Adsorption of inorganic ions from aqueous solutions using mineral sorbent - tripoli

Tomsk Polytechnic University, Tomsk, Russia

^* Corresponding author: nina.b.shakhova@gmail.com

Abstract

The present research considers the adsorption of H2AsO₄^–, CrO₄^2–, Ni²⁺, Fe³⁺ 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 Fe³⁺ ions on tripoli. The adsorption has been explained in terms of Langmuir and Freundlich isotherms. Based on values of correlation coefficients, H₂AsO₄^–, CrO₄^2–, Ni²⁺, Fe³⁺ 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 H2AsO₄^– adsorbing capacity of tripoli. In general, the results indicated that tripoli can be an efficient low-cost sorbent for removing H2AsO₄^–, Ni²⁺, Fe³⁺ ions from aqueous solutions.