Experimental and modelling studies on fixed bed adsorption of As(III) ions from aqueous solution (original) (raw)
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Kinetic characterization of removal of As (III) by mixed adsorbents
Adsorption kinetics for removal of arsenic was carried out by red mud and its mixtures with haematite, china clay and fly ash besides china clay-fly ash at: adsorbate conc., 5.0 mg1 -1 ; particle size of adsorbent, <53 µm; agitation rate, 220 rpm; pH, 8.0; and temp., 30, 40 & 50°C. Data fit into Lagergren equation and adsorption follows first order reaction kinetics. As(III) removal by adsorbents is diffusion controlled. A low value of activation energy indicates flat nature of energy barrier.
Zenodo (CERN European Organization for Nuclear Research), 2023
The core target of this work is to ensure an efficient and low-cost As-removal technique that will remove arsenic acceptably and proficiently. Among Langmuir and Freundlich isotherm models which model is fitted well with the experimental data is also ensured in this research. From the kinetic study, it is known that pH 7 and 3 hours of contact time is the best option for the adsorption of As, and from the isotherm study with different amounts of iron and As, the required amount of iron for higher adsorption of As is evaluated. The adsorption capacity (Ce/qe) for 10 ppm iron concentration was acquired to be 1.111, and the equilibrium concentration of As at the aqueous phase (Ce) was 0.05 ppm for the initial Arsenic concentration of 0.5 ppm. However, for 5ppm Iron, Ce/qe was found to be 0.95238, and Ce was 0.05ppm for an initial As the concentration of 0.5 ppm after two cycles of column study. The adsorption isotherm model is fitted well with the Langmuir isotherm model and not fitted with Freundlich's isotherm.
Fixed-bed Adsorption of Arsenite (As(III)) from Drinking Water: Breakthrough Studies and Modeling
Presence of dissolved arsenic in drinking water has been a major pollution issue across the world. Sadly, many highly arsenic affected areas are heavely populated and have high levels of rural poverty. Hence, a simple, economical, and rapid solution is essential to provide safe, adequate, and affordable drinking water to the rural population. This investigation deals with fixed bed adsorption of arsenite [As(III)] from drinking water by manganese oxide-coated-alumina (MOCA) and activated alumina. Fixed-bed column studies were performed as a function of bed height, initial As(III) concentration and feed flow rate. A direct relationship between bed height and throughput volume was observed whereas a decrease in throughput volume was observed with increase in feed flow rate and initial As(III) concentration. The study reveals that MOCA would be a more effective medium compared to AA to remove As(III) from drinking water. The adsorption dynamics were modeled by bed depth service time (BDST), Bohart-Adams and Thomas model. All the tested models showed good agreement with initial portion of the experimental breakthrough curve. However, Thomas model predicted the data well over entire range of breakthrough curve and the model predicted values for bed capacity were in close agreement with that of the experimental data, irrespective of the operating conditions employed. Hence, the model parameters associated with Thomas model are more appropriate for process design.
REMOVAL OF As(III) AND As(V) FROM AQUEOUS SOLUTION.pdf
This paper presents the results of the removal of arsenite and arsenate ions from an aqueous solution using Fenton modified solid waste vegetable oil industry (SWVOI). Several factors (such as pH, contact time and Fe 2+ /H 2 O 2 ratio, initial arsenic ion concentration and adsorbent concentration) that affect the arsenic ion adsorption on the SWVOI adsorbent material were investigated. The sorption characteristics of the adsorbent material before modification were also studied and compared with those after sorbent modification. Additionally, the influence of experimental conditions on equilibrium Isotherms were observed. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models, and model parameters were evaluated. The adsorption capacity of the adsorbent and arsenic removal efficiency decreased with increasing pH values up to 7. Maximum removal of 84% for As(III) at pH 7 and 78% for As(V) at pH 4 were obtained from arsenical aqueous solutions of 150 µg L -1 using one gram of modified SWVOI.
Chemical Engineering Journal, 2010
An efficient porous adsorbent for arsenic is developed from abundantly available laterite using an optimized acid followed by base treatment methodology. XRD, HRTEM, surface area analyzer and FTIR are used to characterize the treated laterite (TL). Arsenic adsorption capacity of TL is evaluated under varying process conditions in batch mode using synthetic solution of single arsenic species, mixture of both As(III) and As(V) species and real arsenic contaminated groundwater (CGW). The effects of competitive ions like phosphate, silicate, carbonate, etc., on arsenic adsorption using TL are explored in details. Langmuir isotherm is found to be a better fit of the experimental isotherm data of arsenic/TL system. The Langmuir maximum adsorption capacity and constant related to adsorption energy for As(V) and As(III) on TL are found to be 21.6 ± 0.8 mg/g, 20.6 ± 0.5 L/mg and 9.4 ± 0.4 mg/g, 5.0 ± 0.1 L/mg, respectively. The competitive adsorption kinetics of individual arsenic species on TL using mixed arsenic spiked water and CGW are studied by speciation technique. Shrinking core model is applied to match the predicted bulk concentration profile of arsenic with experimental data. The model is applied to evaluate the effective pore diffusivity (D e ) and external mass transfer coefficient (K f ) of arsenic for arsenic/TL system and these values are in the range of 1.3-1.6 × 10 −9 m 2 /s and 0.076-11.25 × 10 −4 m/s, respectively. Fixed bed column runs using 6.5 cm TL bed (empty bed contact time: 2.92 min) is capable to produce ∼3000 bed volume (96.7 L, 1 bed volume = 32.23 mL) of water for effluent concentration at <10 g/L (initial arsenic concentration in CGW: 385 ± 25 g/L). The study reveals that TL is porous and highly efficient adsorbent for both arsenic species.
Taguchi’s Optimizing Technology for Removal of As(III) from Aqueous Solution by Khangar
Asian Journal of Chemistry, 2016
Khangar has been used for the removal of As(III) ions from aqueous solution by adsorption process. Taguchi optimization method was used for optimization of process parameters like pH, adsorbent dose, metal ion concentration and contact time. L16 orthogonal array was used in designing the experiments. Statistical tools viz. signal to noise ratio and analysis of variance have been used at 95 % confidence level for all considered parameters. pH was found to be the most important parameter for removal of As(III) from aqueous solution. The optimum results were obtained at pH 7; adsorbent dose 0.7 g/50 mL; metal ion concentration 20 mg/L and contact time 120 min. SEM and FTIR studies of khangar before and after As(III) adsorption were made in order to understand the nature of adsorption. Comparison of adsorption on different adsorbents has also been included in the manuscript.
Removal of arsenate from water by adsorbents: a comparative case study
Environmental Geochemistry and Health, 2011
Laboratory and field filtration experiments were conducted to study the effectiveness of As(V) removal for five types of adsorbent media. The media included activated alumina (AA), modified activated alumina (MAA), granular ferric hydroxide (GFH), granular ferric oxide (GFO), and granular titanium dioxide (TiO 2). In laboratory batch and column experiments, the synthetic challenge water was used to evaluate the effectiveness for five adsorbents. The results of the batch experiments showed that the As(V) adsorption decreased as follows at pH 6.5: TiO 2 [ GFO [ GFH [ MAA [ AA. At pH 8.5, however, As(V) removal decreased in the following order: GFO = TiO 2 [ GFH [ MAA [ AA. In column experiments, at pH 6.5, the adsorbed As(V) for adsorbents followed the order: TiO 2 [ GFO [ GFH, whereas at pH 8.5 the order became: GFO = TiO 2 [ GFH when the challenge water containing 50 lg/L of As(V) was used. Field filtration experiments were carried out in parallel at a wellhead in New Jersey. Before the effluent arsenic concentration increased to 10 lg/L, approximately 58,000 and 41,500 bed volumes of groundwater containing an average of 47 lg/L of As(V) were treated by the filter system packed with GFO and TiO 2 , respectively. The As(V) adsorption decreased in the following sequence: GFO [ TiO 2 [ GFH [ MAA [ AA. Filtration results demonstrated that GFO and TiO 2 adsorbents could be used as media in small community filtration systems for As(V) removal.
Applied Geochemistry, 2009
Batch and column experiments were conducted on As adsorption from aqueous solution by natural solids to test the feasibility of these materials to act as adsorbents for As removal from groundwater and drinking water. The solids considered are natural hematite and natural siderite. The As species studied are As(V), As(III) and dimethylarsinic acid (DMA). Arsenic(III), As(V) and DMA were removed to different extents by the solids studied from water solutions containing these three As species, with the highest efficiency for As(V). In aqueous solutions with a mixture of As species, adsorption kinetics depend on the species. On both materials, As(V) was preferentially adsorbed in the batches and first reached equilibrium, followed by DMA and As(III). The As adsorption took place more slowly on natural hematite and natural siderite compared with ferrihydrite. The results demonstrate that the amount of As removed from As(III) batches was greater than that from As(V) batches due to a surface alteration of the solids caused by As(III) oxidation. Although the highest efficiency for As retention was observed on hematite HIO1 in the batch experiments, siderite used as column filling was more efficient in removing As from water containing the As species studied in comparison with hematite. The coating of fresh Fe(III)-oxides was much more intensive in the siderite-packed column than in the hematite-packed column. The combination of siderite and hematite would promote the column filling performance in removing As from aqueous solution.
Removal of arsenic from water by different adsorbents
Indian Journal of Chemical Technology, 2004
Present study is carried out for the removal of As(III) from water using commonly available adsorbents such as sand, from Yamuna river ( Delhi ), as well as from Ganga river (Kolkata), activated carbon, Hametite ore and sand -iron scrap mixture. All these adsorbents are used as received but sand and activated carbon which do not show much adsorption for As(III) are modified by treating with different metal ions in order to improve their adsorption efficiency. Results of the laboratory experiments under static conditions have confirmed that iron impregnated granular activated carbon (GAC), spherical activated carbon (SAC) as well as sand - iron scrap mixture have much promise as a medium for the removal of As(III) in drinking water. Various parameters like adsorbent dose, contact time, pH and arsenic concentration are optimized. A simple and economical domestic arsenic removal kit has been designed and successfully evaluated in the laboratory using sand-iron scrap mixture as media fo...