Abstract
The present research considers the adsorption of H2AsO 4 – , CrO 4 2– , Ni 2+ , Fe 3+ ions from their aqueous solutions by mineral sorbent - tripoli. Tripoli was characterized by different physico-chemical methods such as X-ray phase analysis, inductively coupled plasma atomic emission spectrometry, method of thermal desorption of nitrogen. Contact time, specific surface area, specific pore volume and surface charge of tripoli have been determined. The effect of tripoli surface area modification by iron (III) oxide-hydroxide on tripoli sorption capacity for the arsenic anions has been investigated. The maximum adsorption was found to occur within 30 minutes of contact time. Different models including the pseudo-first-order kinetic and the pseudo-second-order kinetic equations were used to analyse kinetic data. All the models being considered, it has been stated that the pseudo-second-order kinetic model is the most appropriate to describe the adsorption behaviour of Fe 3+ ions on tripoli. The adsorption has been explained in terms of Langmuir and Freundlich isotherms. Based on values of correlation coefficients, H 2 AsO 4 – , CrO 4 2– , Ni 2+ , Fe 3+ sorption isotherm data were better fitted by Langmuir model. It has been detected that the modification of mineral sorbent (tripoli) leads to the increase in H2AsO 4 – adsorbing capacity of tripoli. In general, the results indicated that tripoli can be an efficient low-cost sorbent for removing H2AsO 4 – , Ni 2+ , Fe 3+ ions from aqueous solutions.
Highlights
Existing methods for water purification from H2AsO4, CrO42, Ni2+, Fe3+ ions are based on processes of oxidation, sedimentation, coagulation and membrane technologies
To determine the optimal time required for reaching the sorption equilibrium, static adsorption was induced, with different contact time being considered
Equal quantity of 0.05g of dry adsorbent was mixed with 50 mL of the solution with equal initial concentration of Fe3+ ions 20 mg∙L–1 over the periods corresponding to different contact time; and the mixture was centrifuged with the centrifuge «Allegra 64R» (USA) for 10 min at 10000 rpm
Summary
Existing methods for water purification from H2AsO4–, CrO42–, Ni2+, Fe3+ ions are based on processes of oxidation, sedimentation, coagulation and membrane technologies. They cannot be used to reduce concentrations of these ions to permissible levels. The present study is focused upon adsorption of H2AsO4–, CrO42–, Ni2+, Fe3+ ions from their aqueous solutions by mineral sorbent tripoli. The effect of various parameters affecting sorption behaviour such as contact time, specific surface area, tripoli surface charge, modification of the surface area of sorbent has been investigated to better understand the adsorption process and ways of possible usage of the mineral sorbent (tripoli) for wastewater purification
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