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Papers by HAMDİ SONER ALTUNDOĞAN

Fresenius Environmental Bulletin, 2018

Fresenius Environmental Bulletin, 2018

Process Biochemistry, 2005

In this study, a composite adsorbent was prepared from sugar beet pulp by loading with iron (III)... more In this study, a composite adsorbent was prepared from sugar beet pulp by loading with iron (III) hydroxide and its Cr(VI) removal properties from aqueous solutions were investigated. For this purpose, sugar beet pulp was subjected to the treatments of saponification, ferric ...

Journal of Hazardous Materials, 2007

A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas... more A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas formed during carbonization process have been studied for Cr(VI) removal from aqueous solutions. The SO 2 rich gas was shown to be an excellent Cr(VI) reductant. The equilibrium and kinetic studies were conducted by using the carbonaceous adsorbent derived from sugar beet pulp. The lower pH favoured Cr(VI) adsorption but substantial Cr(VI) reduction was observed. The Langmuir and Freundlich isotherm models were applied and the Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacity of chromium calculated from Langmuir isotherm is about 24 mg g −1 for 25 • C. The adsorption of Cr(VI) is an endothermic process and follows the pseudo-second-order rate kinetics. The sulphuric acid-carbonization is an economical method for particularly chromium removal because the gas generated during carbonization exhibits good Cr(VI) reduction properties and carbonaceous material obtained is an efficient Cr(VI) adsorbent.

Waste Management, 2002

Heat treatment and acid treatment methods have been tested on red mud to increase its arsenic ads... more Heat treatment and acid treatment methods have been tested on red mud to increase its arsenic adsorption capability. The results indicate that the adsorptive capacity of red mud can be increased by acid treatment. This treatment causes sodalite compounds to leach out. As(III) and As(V) adsorption characteristics of activated red mud have similar tendencies with raw red mud. Batch adsorption studies have shown that activated red mud in dosages ranging from 20 to 100 g l À1 can be used effectively to remove arsenic from aqueous solutions. The process is pH dependent, the optimum range being 5.8-7.5 for As(III) and 1.8-3.5 for As(V). The maximum removals are 96.52% for As(V) and 87.54% for As(III) for solutions with a final pH of 7.25 and 3.50, respectively, for the initial arsenic concentration of 133.5 mmol l À1 (10 mg l À1), activated red mud dosage of 20 g l À1 , contact time of 60 min and temperature of 25 C. The adsorption data obtained follow a first-order rate expression and fit the Langmuir isotherm well. Isotherms have been used to obtain the thermodynamic parameters. It was found that the adsorption of As(III) was exothermic, whereas As(V) adsorption was endothermic.

Journal of Environmental Science and Health, Part A, 2003

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Environmental Technology, 2004

Hexavalent chromium introduced to the water ecosystem is an important issue due to the toxic effe... more Hexavalent chromium introduced to the water ecosystem is an important issue due to the toxic effect it poses. The first step of conventional treatment of wastewaters containing hexavalent chromium is its reduction to chromium (Ill) which is less toxic. The use of industrial waste material for the reduction of chromium (VI) may be a new cost-effective alternative. In this study, Cr(VI) reduction characteristics of vinasse which is a waste material of alcohol production from sugar beet molasses was investigated. The parameters of pH, temperature, concentrations of initial Cr(VI) and vinasse on the reduction of Cr(VI) were examined as a function of time by applying batch tests. Cr(VI) was almost completely reduced within about 270 min in the concentrations of Cr(VI) and vinasse of 80 mg !"' and 200 ml!"', respectively, at pH 3.0 and 25°C. The results showed that reduction time can be shortened by increasing acidity and vinasse concentration or decreasing Cr(VI) initial concentration. Cr(VI) reduction process was found be obey first order kinetic model of homogenous phase reactions. The temperature was found to have a positive effect on the reduction process and the activation energy of process was calculated as 46.07 kJ mo!"'. Although the detoxification of wastewaters containing Cr(VI) via reducing it to Cr(Ill) by using vinasse seems to be costeffective, the resulting effluent to be produced necessitates a further treatment to reduce organic pollution.

Journal of Hazardous Materials, 2007

Sugar beet pulp was converted into effective copper sorption material by treating subsequently wi... more Sugar beet pulp was converted into effective copper sorption material by treating subsequently with NaOH and citric acid. Compared with the untreated sugar beet pulp, the cation exchange capacity of the modified sugar beet pulp increased from 0.86 to 3.21 mequiv. g −1. Swelling capacity and COD values of modified sugar beet pulp were found to be decreased in the ratio of 38% and 61%, respectively, compared to the corresponding values of native sugar beet pulp, meaning that modification causes stabilization. Sorption characteristics of the modified sugar beet pulp towards copper ions were studied with batch experiments. Pseudo-first, pseudo-second-order and intraparticle kinetic models were applied to the kinetic data and it was found that the sorption processes followed the pseudo-second-order rate kinetics with activation energy of 16.34 kJ mol −1. The equilibration data fit best with the Langmuir isotherm the maximum copper sorption capacity of which is 119.43 mg g −1. The mean free energy of copper sorption process calculated from Dubinin-Radushkevich model and the Polanyi potential concept was found to be in the range of 10.91-11.95 kJ mol −1 showing that the main mechanism governing the sorption process is ion exchange. The negative values found for enthalpy change (−14.797 kJ mol −1 over the range of 25-55 • C) and free energy change (−19.361 kJ mol −1 for 25 • C) indicate that the sorption process is exothermic and spontaneous in nature.

SSRN Electronic Journal, 2022

Waste Management, 1999

The ability of Copper Smelter Slag (CSS) to reduce Cr(VI) in aqueous solutions has been investiga... more The ability of Copper Smelter Slag (CSS) to reduce Cr(VI) in aqueous solutions has been investigated. The extent of reduction is dependent on the amounts of acid and reductant, contact time, Cr(VI) concentration, temperature of the solution and particle size of CSS. The amount of acid is the most important variable aecting the reduction process. When twice the amount of acid required with respect to Cr(VI) was used, Cr(VI) in 100 ml solution (100 mg/l) was completely reduced in a contact period less than 5 min by a 10 g/l dosage of CSS. Reduction eciency increased with increase in temperature of solution, showing that the process is endothermic. Reduced chromium, and iron and other metals dissolved from CSS were eectively precipitated by using NaOH or calcinated carbonatation sludge from sugar plant.

Bioresource Technology, 2008

A cation exchanging material was developed from lemon by modifying the pectic-cellulosic substanc... more A cation exchanging material was developed from lemon by modifying the pectic-cellulosic substances in the lemon peel by lemon juice having citric acid. For this purpose, chopped lemon removed from seeds and yellow skin was heated in two stages, firstly at 50°C for 24 h and subsequently at 120°C for 2 h. The material obtained was ground, repeatedly washed with water and dried. Lemon peel and lemon resin obtained were characterized through physicochemical analyses and FTIR spectroscopy. Heavy metal binding performance of this material was determined by removal tests conducted by using 10 mM solutions of divalent metals. Experimental results show that the resin prepared from lemon is effective especially for Pb and Cu removals. For a lemon resin dosage of 10 g l À1 , sorption affinity of divalent metal ions is found to be in an order of Pb > Cu > Ni > Fe > Cd > Zn > Co > Mn. Typically, sorption capacities are about 0.87 and 0.43 mmol g À1 for Pb and Mn, respectively.

Environmental Pollution, 1997

The reduction of Cr(VI) by steel wool and the precipitation of reduced chromium by CaC03 powder a... more The reduction of Cr(VI) by steel wool and the precipitation of reduced chromium by CaC03 powder and NaOH solution were investigated in continuous and batch systems, respectively. The effects of acid and initial Cr(VI) concentrations, volumetric rate and temperature of solution on Cr(V1) reduction were studied. The results showed that the reduction of Cr(V1), to a large extent, depended on, and increased with, acid concentration. The Cr(III) and iron ions in the reduced solution were completely precipitated by using NaOH solution at appropriate alkaline conditions. It was concluded that CaC03 powder could be used as a cheap precipitant for Cr(III) ions. But the iron ions in the reduced solution could not be fully removed by using this precipitant.

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2013

In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was inve... more In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was investigated in the pressure reactor by using response surface methodology (RSM). Experiments were planned with all factorial array of central composite design (CCD) as total 86 experiments, so that 10 experiments in centre. The all of investigating parameters having affected on the results were defined as independent variable. The investigating parameters that effect on the metal extraction yield in the chalcopyrite leaching are concentration of ammonium persulfate (APS), leaching temperature, stirring speed and ratio of liquid-solid, reactor occupancy and leaching time. Leaching experiments were performed as batch in the 300 ml pressure reactor. The data obtained from different experimental conditions were optimized that optimizing criteria is maximum copper and minimum iron passing into leach solution, and model equation were formed for both response values. The obtained model equations for copper and iron extraction were determined as second order model. Under the optimum leaching conditions, some model solution points were determined. According to results of performed experiments in these solution points, copper extraction yield is 55% while iron is about 15%.

Journal of Hazardous Materials, 2009

Sorption of Cd 2+ , Cr 3+ , Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ onto a carboxyl groups-rich material ... more Sorption of Cd 2+ , Cr 3+ , Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ onto a carboxyl groups-rich material prepared from lemon was investigated in batch systems. The results revealed that the sorption is highly pH dependent. Sorption kinetic data indicated that the equilibrium was achieved in the range of 30-240 min for different metal ions and sorption kinetics followed the pseudo-second-order model for all metals studied. Relative sorption rate of various metal cations was found to be in the general order of Ni 2+ > Cd 2+ > Cu 2+ > Pb 2+ > Zn 2+ > Cr 3+. The binding characteristics of the sorbent for heavy metal ions were analyzed under various conditions and isotherm data was accurately fitted to the Langmuir equation. The metal binding capacity order calculated from Langmuir isotherm was Pb 2+ > Cu 2+ > Ni 2+ > Cd 2+ > Zn 2+ > Cr 3+. The mean free energy of metal sorption process calculated from Dubinin-Radushkevich parameter and the Polanyi potential was found to be in the range of 8-11 kJ mol −1 for the metals studied showing that the main mechanism governing the sorption process seems to be ion exchange. The basic thermodynamic parameters of metals ion sorption process were calculated by using the Langmuir constants obtained from equilibration study. The G • and H • values for metals ion sorption on the lemon sorbent showed the process to be spontaneous and exothermic in nature. Relatively low H • values revealed that physical adsorption significantly contributed to the mechanism.

Environmental Technology, 2001

This study was carried out to reduce Cr(VI) in aqueous solutions by using synthetic iron sulphide... more This study was carried out to reduce Cr(VI) in aqueous solutions by using synthetic iron sulphide. For that purpose, the effects of acid content, contact time, initial Cr(VI) concentration, temperature of the solution, particle size and dosage of iron sulphide on the Cr(VI) reduction were investigated. Reduction extent of Cr(VI) is, to a great extent, dependent on the amount of acid. The Cr(VI) in the solution containing two times the H:zS04 with respect to stoichiometric amount of Cr(VI) was completely reduced within 45 min by using 2.5 g litre'! iron sulphide at 25 0c. The reduction efficiency of Cr(VI) was increased with temperature of solution. The variation in particle size of iron sulphide did not affect the reduction yield of Cr(VI). The total reduction capacity of synthetic iron sulphide was found to be 237.6 mg Cr(VI) g-\ The results related to shrinking particle model showed that the reduction reaction was chemically controlled and activation energy for the process was calculated as 38.4 kJ mol". Cr(VI) compounds known as chromates and dichromates enter waters from many industrial processes such as leather tanning, electroplating, metal cleaning, alloy preparation etc [1]. Cr(VI) is a strong oxidant. It is more

Environmental Technology, 1999

Journal of Chemical Technology & Biotechnology, 2003

In this study, acid treatment and heat treatment methods have been investigated in order to enhan... more In this study, acid treatment and heat treatment methods have been investigated in order to enhance the phosphate adsorption capacity of bauxite. For this purpose, a series of bauxites treated with 0.1-1.0 M HCl and another one heated at various temperatures between 200 and 1000 • C were subjected to standardized orthophosphate adsorption tests. Besides determining chemical and mineralogical compositions, TGA and DTA were performed and point of zero net proton charge (PZNPC), surface area, mean particle size and porosity were measured for selected samples. The results have shown that the acid treatment of bauxite has a negative effect on the phosphate adsorption capability. On the other hand, it has been observed that the phosphate adsorption capacity of bauxite could be increased by heating. The optimum heating temperature was determined as 600 • C. Bauxite heated at 600 • C exhibited about an eight-fold increase in surface area compared with raw bauxite. The results showed that the activation of bauxite occurred via dehydration of boehmite and diaspore, being the hydrated mineral phases. Maximum adsorption efficiencies for ortho-, tripoly-and glycerophosphates were achieved in the slightly acidic pH range. It was found that the adsorption capacities of thermally-activated bauxite for all phosphate species investigated were higher than that of raw bauxite. But the increase in adsorption efficiency is not proportional to the increase in specific surface area. It was found that the relative adsorptivity of phosphate species investigated is in the order of orthophosphate > tripoly(phosphate) > glycerophosphate. In addition, it was found that the desorption trends of these phosphate species were similar to the results obtained for raw bauxite.

Minerals Engineering, 2004

Minerals Engineering, 2004

In this study, to increase the Cr(VI) adsorption capacity of bauxite, heat treatment method was t... more In this study, to increase the Cr(VI) adsorption capacity of bauxite, heat treatment method was tested and the effects of pH, adsorbent dosage, contact time, initial Cr(VI) concentration and temperature on the adsorption of Cr(VI) were investigated. Although heating provides an enhanced adsorption, the heat-activated bauxite was found to be a weak adsorbent for Cr(VI). The maximum adsorption yield (64.9%) was obtained at the conditions of pH 2, activated bauxite dosage of 20 g l À1 , contact time of 180 min, for the initial Cr(VI) concentration of 10 mg l À1 and temperature of 20°C by using the bauxite sample heated at 600°C. The adsorption data fit a first-order rate expression and Langmuir isotherm. Enthalpy, free energy and entropy changes were calculated from the isotherm data. The adsorption of Cr(VI) onto heat-activated bauxite was found to be exothermic.

In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was inve... more In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was investigated in the pressure reactor by using response surface methodology (RSM). Experiments were planned with all factorial array of central composite design (CCD) as total 86 experiments, so that 10 experiments in centre. The all of investigating parameters having affected on the results were defined as independent variable. The investigating parameters that effect on the metal extraction yield in the chalcopyrite leaching are concentration of ammonium persulfate (APS), leaching temperature, stirring speed and ratio of liquid-solid, reactor occupancy and leaching time. Leaching experiments were performed as batch in the 300 ml pressure reactor. The data obtained from different experimental conditions were optimized that optimizing criteria is maximum copper and minimum iron passing into leach solution, and model equation were formed for both response values. The obtained model equations f...

Fresenius Environmental Bulletin, 2018

Fresenius Environmental Bulletin, 2018

Process Biochemistry, 2005

In this study, a composite adsorbent was prepared from sugar beet pulp by loading with iron (III)... more In this study, a composite adsorbent was prepared from sugar beet pulp by loading with iron (III) hydroxide and its Cr(VI) removal properties from aqueous solutions were investigated. For this purpose, sugar beet pulp was subjected to the treatments of saponification, ferric ...

Journal of Hazardous Materials, 2007

A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas... more A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas formed during carbonization process have been studied for Cr(VI) removal from aqueous solutions. The SO 2 rich gas was shown to be an excellent Cr(VI) reductant. The equilibrium and kinetic studies were conducted by using the carbonaceous adsorbent derived from sugar beet pulp. The lower pH favoured Cr(VI) adsorption but substantial Cr(VI) reduction was observed. The Langmuir and Freundlich isotherm models were applied and the Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacity of chromium calculated from Langmuir isotherm is about 24 mg g −1 for 25 • C. The adsorption of Cr(VI) is an endothermic process and follows the pseudo-second-order rate kinetics. The sulphuric acid-carbonization is an economical method for particularly chromium removal because the gas generated during carbonization exhibits good Cr(VI) reduction properties and carbonaceous material obtained is an efficient Cr(VI) adsorbent.

Waste Management, 2002

Heat treatment and acid treatment methods have been tested on red mud to increase its arsenic ads... more Heat treatment and acid treatment methods have been tested on red mud to increase its arsenic adsorption capability. The results indicate that the adsorptive capacity of red mud can be increased by acid treatment. This treatment causes sodalite compounds to leach out. As(III) and As(V) adsorption characteristics of activated red mud have similar tendencies with raw red mud. Batch adsorption studies have shown that activated red mud in dosages ranging from 20 to 100 g l À1 can be used effectively to remove arsenic from aqueous solutions. The process is pH dependent, the optimum range being 5.8-7.5 for As(III) and 1.8-3.5 for As(V). The maximum removals are 96.52% for As(V) and 87.54% for As(III) for solutions with a final pH of 7.25 and 3.50, respectively, for the initial arsenic concentration of 133.5 mmol l À1 (10 mg l À1), activated red mud dosage of 20 g l À1 , contact time of 60 min and temperature of 25 C. The adsorption data obtained follow a first-order rate expression and fit the Langmuir isotherm well. Isotherms have been used to obtain the thermodynamic parameters. It was found that the adsorption of As(III) was exothermic, whereas As(V) adsorption was endothermic.

Journal of Environmental Science and Health, Part A, 2003

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Environmental Technology, 2004

Hexavalent chromium introduced to the water ecosystem is an important issue due to the toxic effe... more Hexavalent chromium introduced to the water ecosystem is an important issue due to the toxic effect it poses. The first step of conventional treatment of wastewaters containing hexavalent chromium is its reduction to chromium (Ill) which is less toxic. The use of industrial waste material for the reduction of chromium (VI) may be a new cost-effective alternative. In this study, Cr(VI) reduction characteristics of vinasse which is a waste material of alcohol production from sugar beet molasses was investigated. The parameters of pH, temperature, concentrations of initial Cr(VI) and vinasse on the reduction of Cr(VI) were examined as a function of time by applying batch tests. Cr(VI) was almost completely reduced within about 270 min in the concentrations of Cr(VI) and vinasse of 80 mg !"' and 200 ml!"', respectively, at pH 3.0 and 25°C. The results showed that reduction time can be shortened by increasing acidity and vinasse concentration or decreasing Cr(VI) initial concentration. Cr(VI) reduction process was found be obey first order kinetic model of homogenous phase reactions. The temperature was found to have a positive effect on the reduction process and the activation energy of process was calculated as 46.07 kJ mo!"'. Although the detoxification of wastewaters containing Cr(VI) via reducing it to Cr(Ill) by using vinasse seems to be costeffective, the resulting effluent to be produced necessitates a further treatment to reduce organic pollution.

Journal of Hazardous Materials, 2007

Sugar beet pulp was converted into effective copper sorption material by treating subsequently wi... more Sugar beet pulp was converted into effective copper sorption material by treating subsequently with NaOH and citric acid. Compared with the untreated sugar beet pulp, the cation exchange capacity of the modified sugar beet pulp increased from 0.86 to 3.21 mequiv. g −1. Swelling capacity and COD values of modified sugar beet pulp were found to be decreased in the ratio of 38% and 61%, respectively, compared to the corresponding values of native sugar beet pulp, meaning that modification causes stabilization. Sorption characteristics of the modified sugar beet pulp towards copper ions were studied with batch experiments. Pseudo-first, pseudo-second-order and intraparticle kinetic models were applied to the kinetic data and it was found that the sorption processes followed the pseudo-second-order rate kinetics with activation energy of 16.34 kJ mol −1. The equilibration data fit best with the Langmuir isotherm the maximum copper sorption capacity of which is 119.43 mg g −1. The mean free energy of copper sorption process calculated from Dubinin-Radushkevich model and the Polanyi potential concept was found to be in the range of 10.91-11.95 kJ mol −1 showing that the main mechanism governing the sorption process is ion exchange. The negative values found for enthalpy change (−14.797 kJ mol −1 over the range of 25-55 • C) and free energy change (−19.361 kJ mol −1 for 25 • C) indicate that the sorption process is exothermic and spontaneous in nature.

SSRN Electronic Journal, 2022

Waste Management, 1999

The ability of Copper Smelter Slag (CSS) to reduce Cr(VI) in aqueous solutions has been investiga... more The ability of Copper Smelter Slag (CSS) to reduce Cr(VI) in aqueous solutions has been investigated. The extent of reduction is dependent on the amounts of acid and reductant, contact time, Cr(VI) concentration, temperature of the solution and particle size of CSS. The amount of acid is the most important variable aecting the reduction process. When twice the amount of acid required with respect to Cr(VI) was used, Cr(VI) in 100 ml solution (100 mg/l) was completely reduced in a contact period less than 5 min by a 10 g/l dosage of CSS. Reduction eciency increased with increase in temperature of solution, showing that the process is endothermic. Reduced chromium, and iron and other metals dissolved from CSS were eectively precipitated by using NaOH or calcinated carbonatation sludge from sugar plant.

Bioresource Technology, 2008

A cation exchanging material was developed from lemon by modifying the pectic-cellulosic substanc... more A cation exchanging material was developed from lemon by modifying the pectic-cellulosic substances in the lemon peel by lemon juice having citric acid. For this purpose, chopped lemon removed from seeds and yellow skin was heated in two stages, firstly at 50°C for 24 h and subsequently at 120°C for 2 h. The material obtained was ground, repeatedly washed with water and dried. Lemon peel and lemon resin obtained were characterized through physicochemical analyses and FTIR spectroscopy. Heavy metal binding performance of this material was determined by removal tests conducted by using 10 mM solutions of divalent metals. Experimental results show that the resin prepared from lemon is effective especially for Pb and Cu removals. For a lemon resin dosage of 10 g l À1 , sorption affinity of divalent metal ions is found to be in an order of Pb > Cu > Ni > Fe > Cd > Zn > Co > Mn. Typically, sorption capacities are about 0.87 and 0.43 mmol g À1 for Pb and Mn, respectively.

Environmental Pollution, 1997

The reduction of Cr(VI) by steel wool and the precipitation of reduced chromium by CaC03 powder a... more The reduction of Cr(VI) by steel wool and the precipitation of reduced chromium by CaC03 powder and NaOH solution were investigated in continuous and batch systems, respectively. The effects of acid and initial Cr(VI) concentrations, volumetric rate and temperature of solution on Cr(V1) reduction were studied. The results showed that the reduction of Cr(V1), to a large extent, depended on, and increased with, acid concentration. The Cr(III) and iron ions in the reduced solution were completely precipitated by using NaOH solution at appropriate alkaline conditions. It was concluded that CaC03 powder could be used as a cheap precipitant for Cr(III) ions. But the iron ions in the reduced solution could not be fully removed by using this precipitant.

SAÜ Fen Bilimleri Enstitüsü Dergisi, 2013

In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was inve... more In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was investigated in the pressure reactor by using response surface methodology (RSM). Experiments were planned with all factorial array of central composite design (CCD) as total 86 experiments, so that 10 experiments in centre. The all of investigating parameters having affected on the results were defined as independent variable. The investigating parameters that effect on the metal extraction yield in the chalcopyrite leaching are concentration of ammonium persulfate (APS), leaching temperature, stirring speed and ratio of liquid-solid, reactor occupancy and leaching time. Leaching experiments were performed as batch in the 300 ml pressure reactor. The data obtained from different experimental conditions were optimized that optimizing criteria is maximum copper and minimum iron passing into leach solution, and model equation were formed for both response values. The obtained model equations for copper and iron extraction were determined as second order model. Under the optimum leaching conditions, some model solution points were determined. According to results of performed experiments in these solution points, copper extraction yield is 55% while iron is about 15%.

Journal of Hazardous Materials, 2009

Sorption of Cd 2+ , Cr 3+ , Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ onto a carboxyl groups-rich material ... more Sorption of Cd 2+ , Cr 3+ , Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ onto a carboxyl groups-rich material prepared from lemon was investigated in batch systems. The results revealed that the sorption is highly pH dependent. Sorption kinetic data indicated that the equilibrium was achieved in the range of 30-240 min for different metal ions and sorption kinetics followed the pseudo-second-order model for all metals studied. Relative sorption rate of various metal cations was found to be in the general order of Ni 2+ > Cd 2+ > Cu 2+ > Pb 2+ > Zn 2+ > Cr 3+. The binding characteristics of the sorbent for heavy metal ions were analyzed under various conditions and isotherm data was accurately fitted to the Langmuir equation. The metal binding capacity order calculated from Langmuir isotherm was Pb 2+ > Cu 2+ > Ni 2+ > Cd 2+ > Zn 2+ > Cr 3+. The mean free energy of metal sorption process calculated from Dubinin-Radushkevich parameter and the Polanyi potential was found to be in the range of 8-11 kJ mol −1 for the metals studied showing that the main mechanism governing the sorption process seems to be ion exchange. The basic thermodynamic parameters of metals ion sorption process were calculated by using the Langmuir constants obtained from equilibration study. The G • and H • values for metals ion sorption on the lemon sorbent showed the process to be spontaneous and exothermic in nature. Relatively low H • values revealed that physical adsorption significantly contributed to the mechanism.

Environmental Technology, 2001

This study was carried out to reduce Cr(VI) in aqueous solutions by using synthetic iron sulphide... more This study was carried out to reduce Cr(VI) in aqueous solutions by using synthetic iron sulphide. For that purpose, the effects of acid content, contact time, initial Cr(VI) concentration, temperature of the solution, particle size and dosage of iron sulphide on the Cr(VI) reduction were investigated. Reduction extent of Cr(VI) is, to a great extent, dependent on the amount of acid. The Cr(VI) in the solution containing two times the H:zS04 with respect to stoichiometric amount of Cr(VI) was completely reduced within 45 min by using 2.5 g litre'! iron sulphide at 25 0c. The reduction efficiency of Cr(VI) was increased with temperature of solution. The variation in particle size of iron sulphide did not affect the reduction yield of Cr(VI). The total reduction capacity of synthetic iron sulphide was found to be 237.6 mg Cr(VI) g-\ The results related to shrinking particle model showed that the reduction reaction was chemically controlled and activation energy for the process was calculated as 38.4 kJ mol". Cr(VI) compounds known as chromates and dichromates enter waters from many industrial processes such as leather tanning, electroplating, metal cleaning, alloy preparation etc [1]. Cr(VI) is a strong oxidant. It is more

Environmental Technology, 1999

Journal of Chemical Technology & Biotechnology, 2003

In this study, acid treatment and heat treatment methods have been investigated in order to enhan... more In this study, acid treatment and heat treatment methods have been investigated in order to enhance the phosphate adsorption capacity of bauxite. For this purpose, a series of bauxites treated with 0.1-1.0 M HCl and another one heated at various temperatures between 200 and 1000 • C were subjected to standardized orthophosphate adsorption tests. Besides determining chemical and mineralogical compositions, TGA and DTA were performed and point of zero net proton charge (PZNPC), surface area, mean particle size and porosity were measured for selected samples. The results have shown that the acid treatment of bauxite has a negative effect on the phosphate adsorption capability. On the other hand, it has been observed that the phosphate adsorption capacity of bauxite could be increased by heating. The optimum heating temperature was determined as 600 • C. Bauxite heated at 600 • C exhibited about an eight-fold increase in surface area compared with raw bauxite. The results showed that the activation of bauxite occurred via dehydration of boehmite and diaspore, being the hydrated mineral phases. Maximum adsorption efficiencies for ortho-, tripoly-and glycerophosphates were achieved in the slightly acidic pH range. It was found that the adsorption capacities of thermally-activated bauxite for all phosphate species investigated were higher than that of raw bauxite. But the increase in adsorption efficiency is not proportional to the increase in specific surface area. It was found that the relative adsorptivity of phosphate species investigated is in the order of orthophosphate > tripoly(phosphate) > glycerophosphate. In addition, it was found that the desorption trends of these phosphate species were similar to the results obtained for raw bauxite.

Minerals Engineering, 2004

Minerals Engineering, 2004

In this study, to increase the Cr(VI) adsorption capacity of bauxite, heat treatment method was t... more In this study, to increase the Cr(VI) adsorption capacity of bauxite, heat treatment method was tested and the effects of pH, adsorbent dosage, contact time, initial Cr(VI) concentration and temperature on the adsorption of Cr(VI) were investigated. Although heating provides an enhanced adsorption, the heat-activated bauxite was found to be a weak adsorbent for Cr(VI). The maximum adsorption yield (64.9%) was obtained at the conditions of pH 2, activated bauxite dosage of 20 g l À1 , contact time of 180 min, for the initial Cr(VI) concentration of 10 mg l À1 and temperature of 20°C by using the bauxite sample heated at 600°C. The adsorption data fit a first-order rate expression and Langmuir isotherm. Enthalpy, free energy and entropy changes were calculated from the isotherm data. The adsorption of Cr(VI) onto heat-activated bauxite was found to be exothermic.

In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was inve... more In this study, ammonium persulfate leaching of metals from Kure chalcopyrite concentrate was investigated in the pressure reactor by using response surface methodology (RSM). Experiments were planned with all factorial array of central composite design (CCD) as total 86 experiments, so that 10 experiments in centre. The all of investigating parameters having affected on the results were defined as independent variable. The investigating parameters that effect on the metal extraction yield in the chalcopyrite leaching are concentration of ammonium persulfate (APS), leaching temperature, stirring speed and ratio of liquid-solid, reactor occupancy and leaching time. Leaching experiments were performed as batch in the 300 ml pressure reactor. The data obtained from different experimental conditions were optimized that optimizing criteria is maximum copper and minimum iron passing into leach solution, and model equation were formed for both response values. The obtained model equations f...