Norita Mohamed - Academia.edu (original) (raw)

Papers by Norita Mohamed

Water Science & Technology

This study was conducted to: (1) evaluate the performance of constructed wetlands in removing Zn,... more This study was conducted to: (1) evaluate the performance of constructed wetlands in removing Zn, Pb and Cd, respectively, and Zn, Pb, Cd and Cu in combination and (2) investigate the speciation patterns of the dissolved metals differentiated according to their detectability by anodic stripping voltammetry (ASV) and their lability towards Chelex resin along the treatment path of metal-containing wastewater in horizontal subsurface-flow constructed wetlands. Four laboratory scale wetland units planted with cattails (Typha latifolia) were operated outdoors for six months. Three of the units were, respectively, fed with primary-treated domestic wastewater spiked with Zn(II), Pb(II) and Cd(II) whilst the fourth was spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II). The results demonstrate that a metal removal efficiency of over 99% was achievable for wetland units treating the metals singly or in combination provided the sorption capacity of the media was not exceeded. When...

Talanta, 1979

Fifteen new hydrazones with one or more ferroin groups were prepared, and their chelation and chr... more Fifteen new hydrazones with one or more ferroin groups were prepared, and their chelation and chromogenic properties with iron(II), copper(I), cobalt(II) and nickel(II) were investigated. Improved sensitivity in the spectrophotometric determination of cobalt, copper, and nickel is provided by several of the new compounds. Several others are capable of forming unusually stable and interesting binuclear iron(II) complexes.

Science of The Total Environment, 2003

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as ... more The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails (Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater at a constant flow rate of 25 ml/min. After 6 months, three of the wetland units were fed with the same type of wastewater spiked with Zn(II), Pb(II) and Cd(II), respectively, at 20, 5 and 1 mg/l for a further 9 months. The remaining unit was fed with the same type of wastewater spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II) at concentrations of 10, 2.5, 0.5 and 5 mg/l, respectively, over the same period. The chemical oxygen demand (COD) and ammoniacal nitrogen (AN) concentrations were monitored at the inlet, outlet and three additional locations along the length of the wetland units to assess the performance of the wetland units at various metal loadings. At the end of the study, all cattail plants were harvested for the determination of total Kjeldahl nitrogen and metal concentrations. The results showed that the COD removal efficiency was practically independent of increasing metal loading or a combination of metal loadings during the duration of the study. In contrast, the AN removal efficiency deteriorated progressively with increasing metal loading. The relative effect of the heavy metals was found to increase in the order: Zn<Pb<Cd and the synergistic effect of metals was not observed. The metals seem to exhibit some inhibitory effect on nitrogen uptake by cattail plants as indicated by lower nitrogen uptake rates in comparison to rates recorded in wetland systems treating domestic wastewater only.

The speciation studies of Cd species in the presence of organic ligands such as humic acid (HA) w... more The speciation studies of Cd species in the presence of organic ligands such as humic acid (HA) were investigated based on a combination of physical characterization by size fractionation using ultrafiltration and chemical characterization by retention studies on different solid sorbents. The aim of this study is to distinguish the labilities of complexed Cd-HA among species with different chemical behaviors at different pH conditions. A set of three columns packed with different substrates, namely, a chelating ion exchange resin Chelex-100, an anion exchange resin Dowex l-X8 and C-18 reversed phase was developed. The retention behavior of the complexes was compared according to their labilities onto the substrates as a function of pH. The applicability of the method to synthetic river water (SRW) sample spiked with Cd species in the presence of humic acid (HA) was demonstrated.

Journal of Coatings Technology and Research, Oct 5, 2010

In this work, Cu-P-SiC composite coatings were deposited via electroless plating with the additio... more In this work, Cu-P-SiC composite coatings were deposited via electroless plating with the addition of sodium hypophoshite (NaH 2 PO 2 ) as a reducing agent. The coating compositions deposited were determined by using energy dispersive X-ray spectroscopy (EDX). The surface morphology of the coatings that were analyzed using scanning electron microscopy (SEM) showed that SiC particles were uniformly distributed by virtue of surfactant addition and mechanical stirring. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings in NaCl and HCl solutions were investigated by the weight loss and potentiodynamic polarization techniques. The results showed that the corrosion resistance of Cu-P-SiC coatings was superior to that of electroless Cu-P coatings and carbon steel substrates in various concentrations of NaCl and HCl solutions.

The Cu-P and Cu-P-SiC composite coatings on carbon steel substrates were deposited via electroles... more The Cu-P and Cu-P-SiC composite coatings on carbon steel substrates were deposited via electroless plating. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings were studied in 3.5% NaCl solution. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings were investigated in 3.5% NaCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. It has been found that the shift in the corrosion potential (E corr ) towards the noble direction, decrease in the corrosion current density (I corr ), increase in the charge transfer resistance (R ct ) and decrease in the double layer capacitance (C dl ) values indicated an improvement in corrosion resistance with the incorporation of SiC particles in the Cu-P matrix. The effects of varying the SiC concentration on the corrosion resistance of carbon steel were investigated and it was found that the best anti-corrosion property of Cu-P-SiC is at 5 g L À1 SiC in the bath formulation.

Materials Chemistry and Physics, Oct 1, 2011

The present paper aims to compare the corrosion resistance of the electroless Cu-P-SiC with Cu-P ... more The present paper aims to compare the corrosion resistance of the electroless Cu-P-SiC with Cu-P composite coating on carbon steel in 1 M HCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopic (EIS) techniques. The study reveals that, the corrosion current density (I corr ) and the double layer capacitance (C dl ) values decrease, the charge transfer resistance (R ct ) and inhibition of efficiencies (IE %) increase with the incorporation of SiC particles in the Cu-P matrix indicating the improvement in corrosion resistance.

Agenda 21 of UNESCO's Decade of Education for Sustainable Development (2005-2014) is centred ... more Agenda 21 of UNESCO's Decade of Education for Sustainable Development (2005-2014) is centred on man and calls for humankind to change behaviours to attain sustainability. Education plays a critical role in realising sustainable development and promoting the capability of the people to address environmental issues towards improving the quality of life for the present and future generations. One approach that could be adopted to attain this goal is through greening the chemistry curriculum particularly the practical work. Green chemistry can contribute to sustainable development through application and extension of its 12 principles. The interdisciplinary nature of green chemistry which embeds economical, environmental and societal dimension is a student centred deep learning approach. However, the success of green chemistry depends on the training and education of a new generation of chemists. Hence, there is a need to educate our teachers with the principles of green chemistry a...

Materials Science and Engineering: B, 2015

This paper highlights the effect of iron impregnation and surface oxidation on the physicochemica... more This paper highlights the effect of iron impregnation and surface oxidation on the physicochemical characteristics of iron impregnated carbon materials. These materials were characterized by various techniques like surface area, pore size distribution, SEM/EDX, CHN, XRD, FTIR, TG/DT, VSM and XPS analyses. The increase in the surface functionalities and pores diameter (3.51-5.49 nm) of the iron-impregnated carbon materials was observed with the increase in iron contents and surface oxidation. The saturated magnetization values (0.029-0.034 emu/g) for the iron-impregnated carbon materials reflected the magnetic tendency due to the development of small size iron oxides on their surfaces. The XPS spectra revealed the existence of different oxidation states of the corresponding metals on the iron impregnated carbon materials. The percentage removal of model dyes (Methylene Blue and Methyl Orange) by iron-impregnated carbon materials was enhanced (>90%) with the increase in iron contents and pores diameters.

Electrochimica Acta, 2014

The electrochemical behavior of a Pt-Cu (copper-platinum) electrode on the electroreduction of ni... more The electrochemical behavior of a Pt-Cu (copper-platinum) electrode on the electroreduction of nitrate and nitrite ions has been investigated in an alkaline medium (0.05 M NaOH) in the presence of 5 mM sodium inositol phytate (NaIP 6 ). Different electrode materials (Cu, Pt, and Pt-Cu) were used to study their activity and selectivity towards the electroreduction of nitrates and nitrites using cyclic voltammetry. The Pt-Cu electrode shows the best performance. The addition of NaIP 6 is to prevent the oxidation of copper atoms to copper ions. The effect of NaIP 6 on the optimization of the electrode activity and stability was investigated in this study. The presence of NaIP 6 further improves the performance of the Pt-Cu electrode especially the stability of the electrode. The final nitrate and nitrite reduction product is ammonia (NH 3 ) which was observed both in the presence and absence of NaIP 6 , although different mechanism pathways are assumed to have taken place in both systems.

PloS one, 2015

In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation an... more In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7-10. Although the reaction kinetics was pseudo-second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effec...

Applied Catalysis A: General, 2014

The electrocatalytic reduction of NO 3 − and its intermediate NO 2 − in neutral medium was perfor... more The electrocatalytic reduction of NO 3 − and its intermediate NO 2 − in neutral medium was performed at a Cu-immobilized Pt surface. The voltammetric investigations showed that the bare Cu electrode has little effect on nitrate reduction reactions (NRR) whereas an enhanced catalytic effect (i.e. a positive shift of the peak potential and an increased reduction current) was observed when Cu particles were immobilized onto Pt surface. At the Cu-Pt electrode surface, the NRR process was observed to occur via a two-step reduction mechanism with a transfer of 2 and 6 electrons in the first and second steps, respectively. Similar results were obtained by chronoamperometric (CA) studies. Closer NRR mechanistic studies at the as prepared Cu-Pt electrode revealed concentration-dependent kinetics with a "critical" nitrate ion concentration of ca. 0.02 M. Moreover, NRR proceeded via a simple adsorption-desorption mechanism following a Langmuir isotherm with an adsorption Gibbs free-energy of ca. −10.16 kJ mol −1 (1st step) and ca. −10.05 kJ mol −1 (2nd step). By means of a Pt|Nafion|Cu-Pt type reactor without any supporting electrolyte, bulk electrolysis was performed to identify nitrate reduction products. It was found that after 180 min of electrolysis, 51% of NO 3 − was converted into NO 2 − intermediate. This percentage decreased to 30% in CO 2 buffered conditions. However, when a tri-metallic Pt-Pd-Cu electrode was employed as a cathode, all of the NO 2 − produced could be successfully converted into NH 3 and N 2 . The electrocatalysis of nitrate ion on Cu-Pt electrode surface showed no apparent surface poisoning as confirmed by its stability after excessive CV runs. This was further supported by surface analysis and morphology of the as-prepared catalyst with scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis.

... and their skills in handling the equipment were markedly improved after adoption of this ... ... more ... and their skills in handling the equipment were markedly improved after adoption of this ... economical, student centered, interesting and time saving, stimulates enjoyment in learning chemistry and ... In: M. Ismail, S.Osman, and HMYunus (Eds), Proceedings for Seminar Pendidikan ...

Water Science & Technology

This study was conducted to: (1) evaluate the performance of constructed wetlands in removing Zn,... more This study was conducted to: (1) evaluate the performance of constructed wetlands in removing Zn, Pb and Cd, respectively, and Zn, Pb, Cd and Cu in combination and (2) investigate the speciation patterns of the dissolved metals differentiated according to their detectability by anodic stripping voltammetry (ASV) and their lability towards Chelex resin along the treatment path of metal-containing wastewater in horizontal subsurface-flow constructed wetlands. Four laboratory scale wetland units planted with cattails (Typha latifolia) were operated outdoors for six months. Three of the units were, respectively, fed with primary-treated domestic wastewater spiked with Zn(II), Pb(II) and Cd(II) whilst the fourth was spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II). The results demonstrate that a metal removal efficiency of over 99% was achievable for wetland units treating the metals singly or in combination provided the sorption capacity of the media was not exceeded. When...

Talanta, 1979

Fifteen new hydrazones with one or more ferroin groups were prepared, and their chelation and chr... more Fifteen new hydrazones with one or more ferroin groups were prepared, and their chelation and chromogenic properties with iron(II), copper(I), cobalt(II) and nickel(II) were investigated. Improved sensitivity in the spectrophotometric determination of cobalt, copper, and nickel is provided by several of the new compounds. Several others are capable of forming unusually stable and interesting binuclear iron(II) complexes.

Science of The Total Environment, 2003

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as ... more The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails (Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater at a constant flow rate of 25 ml/min. After 6 months, three of the wetland units were fed with the same type of wastewater spiked with Zn(II), Pb(II) and Cd(II), respectively, at 20, 5 and 1 mg/l for a further 9 months. The remaining unit was fed with the same type of wastewater spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II) at concentrations of 10, 2.5, 0.5 and 5 mg/l, respectively, over the same period. The chemical oxygen demand (COD) and ammoniacal nitrogen (AN) concentrations were monitored at the inlet, outlet and three additional locations along the length of the wetland units to assess the performance of the wetland units at various metal loadings. At the end of the study, all cattail plants were harvested for the determination of total Kjeldahl nitrogen and metal concentrations. The results showed that the COD removal efficiency was practically independent of increasing metal loading or a combination of metal loadings during the duration of the study. In contrast, the AN removal efficiency deteriorated progressively with increasing metal loading. The relative effect of the heavy metals was found to increase in the order: Zn<Pb<Cd and the synergistic effect of metals was not observed. The metals seem to exhibit some inhibitory effect on nitrogen uptake by cattail plants as indicated by lower nitrogen uptake rates in comparison to rates recorded in wetland systems treating domestic wastewater only.

The speciation studies of Cd species in the presence of organic ligands such as humic acid (HA) w... more The speciation studies of Cd species in the presence of organic ligands such as humic acid (HA) were investigated based on a combination of physical characterization by size fractionation using ultrafiltration and chemical characterization by retention studies on different solid sorbents. The aim of this study is to distinguish the labilities of complexed Cd-HA among species with different chemical behaviors at different pH conditions. A set of three columns packed with different substrates, namely, a chelating ion exchange resin Chelex-100, an anion exchange resin Dowex l-X8 and C-18 reversed phase was developed. The retention behavior of the complexes was compared according to their labilities onto the substrates as a function of pH. The applicability of the method to synthetic river water (SRW) sample spiked with Cd species in the presence of humic acid (HA) was demonstrated.

Journal of Coatings Technology and Research, Oct 5, 2010

In this work, Cu-P-SiC composite coatings were deposited via electroless plating with the additio... more In this work, Cu-P-SiC composite coatings were deposited via electroless plating with the addition of sodium hypophoshite (NaH 2 PO 2 ) as a reducing agent. The coating compositions deposited were determined by using energy dispersive X-ray spectroscopy (EDX). The surface morphology of the coatings that were analyzed using scanning electron microscopy (SEM) showed that SiC particles were uniformly distributed by virtue of surfactant addition and mechanical stirring. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings in NaCl and HCl solutions were investigated by the weight loss and potentiodynamic polarization techniques. The results showed that the corrosion resistance of Cu-P-SiC coatings was superior to that of electroless Cu-P coatings and carbon steel substrates in various concentrations of NaCl and HCl solutions.

The Cu-P and Cu-P-SiC composite coatings on carbon steel substrates were deposited via electroles... more The Cu-P and Cu-P-SiC composite coatings on carbon steel substrates were deposited via electroless plating. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings were studied in 3.5% NaCl solution. The anti-corrosion properties of Cu-P and Cu-P-SiC coatings were investigated in 3.5% NaCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. It has been found that the shift in the corrosion potential (E corr ) towards the noble direction, decrease in the corrosion current density (I corr ), increase in the charge transfer resistance (R ct ) and decrease in the double layer capacitance (C dl ) values indicated an improvement in corrosion resistance with the incorporation of SiC particles in the Cu-P matrix. The effects of varying the SiC concentration on the corrosion resistance of carbon steel were investigated and it was found that the best anti-corrosion property of Cu-P-SiC is at 5 g L À1 SiC in the bath formulation.

Materials Chemistry and Physics, Oct 1, 2011

The present paper aims to compare the corrosion resistance of the electroless Cu-P-SiC with Cu-P ... more The present paper aims to compare the corrosion resistance of the electroless Cu-P-SiC with Cu-P composite coating on carbon steel in 1 M HCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopic (EIS) techniques. The study reveals that, the corrosion current density (I corr ) and the double layer capacitance (C dl ) values decrease, the charge transfer resistance (R ct ) and inhibition of efficiencies (IE %) increase with the incorporation of SiC particles in the Cu-P matrix indicating the improvement in corrosion resistance.

Agenda 21 of UNESCO's Decade of Education for Sustainable Development (2005-2014) is centred ... more Agenda 21 of UNESCO's Decade of Education for Sustainable Development (2005-2014) is centred on man and calls for humankind to change behaviours to attain sustainability. Education plays a critical role in realising sustainable development and promoting the capability of the people to address environmental issues towards improving the quality of life for the present and future generations. One approach that could be adopted to attain this goal is through greening the chemistry curriculum particularly the practical work. Green chemistry can contribute to sustainable development through application and extension of its 12 principles. The interdisciplinary nature of green chemistry which embeds economical, environmental and societal dimension is a student centred deep learning approach. However, the success of green chemistry depends on the training and education of a new generation of chemists. Hence, there is a need to educate our teachers with the principles of green chemistry a...

Materials Science and Engineering: B, 2015

This paper highlights the effect of iron impregnation and surface oxidation on the physicochemica... more This paper highlights the effect of iron impregnation and surface oxidation on the physicochemical characteristics of iron impregnated carbon materials. These materials were characterized by various techniques like surface area, pore size distribution, SEM/EDX, CHN, XRD, FTIR, TG/DT, VSM and XPS analyses. The increase in the surface functionalities and pores diameter (3.51-5.49 nm) of the iron-impregnated carbon materials was observed with the increase in iron contents and surface oxidation. The saturated magnetization values (0.029-0.034 emu/g) for the iron-impregnated carbon materials reflected the magnetic tendency due to the development of small size iron oxides on their surfaces. The XPS spectra revealed the existence of different oxidation states of the corresponding metals on the iron impregnated carbon materials. The percentage removal of model dyes (Methylene Blue and Methyl Orange) by iron-impregnated carbon materials was enhanced (>90%) with the increase in iron contents and pores diameters.

Electrochimica Acta, 2014

The electrochemical behavior of a Pt-Cu (copper-platinum) electrode on the electroreduction of ni... more The electrochemical behavior of a Pt-Cu (copper-platinum) electrode on the electroreduction of nitrate and nitrite ions has been investigated in an alkaline medium (0.05 M NaOH) in the presence of 5 mM sodium inositol phytate (NaIP 6 ). Different electrode materials (Cu, Pt, and Pt-Cu) were used to study their activity and selectivity towards the electroreduction of nitrates and nitrites using cyclic voltammetry. The Pt-Cu electrode shows the best performance. The addition of NaIP 6 is to prevent the oxidation of copper atoms to copper ions. The effect of NaIP 6 on the optimization of the electrode activity and stability was investigated in this study. The presence of NaIP 6 further improves the performance of the Pt-Cu electrode especially the stability of the electrode. The final nitrate and nitrite reduction product is ammonia (NH 3 ) which was observed both in the presence and absence of NaIP 6 , although different mechanism pathways are assumed to have taken place in both systems.

PloS one, 2015

In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation an... more In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7-10. Although the reaction kinetics was pseudo-second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effec...

Applied Catalysis A: General, 2014

The electrocatalytic reduction of NO 3 − and its intermediate NO 2 − in neutral medium was perfor... more The electrocatalytic reduction of NO 3 − and its intermediate NO 2 − in neutral medium was performed at a Cu-immobilized Pt surface. The voltammetric investigations showed that the bare Cu electrode has little effect on nitrate reduction reactions (NRR) whereas an enhanced catalytic effect (i.e. a positive shift of the peak potential and an increased reduction current) was observed when Cu particles were immobilized onto Pt surface. At the Cu-Pt electrode surface, the NRR process was observed to occur via a two-step reduction mechanism with a transfer of 2 and 6 electrons in the first and second steps, respectively. Similar results were obtained by chronoamperometric (CA) studies. Closer NRR mechanistic studies at the as prepared Cu-Pt electrode revealed concentration-dependent kinetics with a "critical" nitrate ion concentration of ca. 0.02 M. Moreover, NRR proceeded via a simple adsorption-desorption mechanism following a Langmuir isotherm with an adsorption Gibbs free-energy of ca. −10.16 kJ mol −1 (1st step) and ca. −10.05 kJ mol −1 (2nd step). By means of a Pt|Nafion|Cu-Pt type reactor without any supporting electrolyte, bulk electrolysis was performed to identify nitrate reduction products. It was found that after 180 min of electrolysis, 51% of NO 3 − was converted into NO 2 − intermediate. This percentage decreased to 30% in CO 2 buffered conditions. However, when a tri-metallic Pt-Pd-Cu electrode was employed as a cathode, all of the NO 2 − produced could be successfully converted into NH 3 and N 2 . The electrocatalysis of nitrate ion on Cu-Pt electrode surface showed no apparent surface poisoning as confirmed by its stability after excessive CV runs. This was further supported by surface analysis and morphology of the as-prepared catalyst with scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis.

... and their skills in handling the equipment were markedly improved after adoption of this ... ... more ... and their skills in handling the equipment were markedly improved after adoption of this ... economical, student centered, interesting and time saving, stimulates enjoyment in learning chemistry and ... In: M. Ismail, S.Osman, and HMYunus (Eds), Proceedings for Seminar Pendidikan ...