Removal of copper from aqueous solutions by low cost adsorbent-Kolubara lignite

Serbian lignite from “Kolubara” deposit was used as a low cost adsorbent for removal of copper ions (Cu2 +) from aqueous solutions. Lignite was subjected to the elementary and technical analysis as well as BET and FTIR analysis due to complete characterization. Basic comparison between lignite and activated carbon was also done. As a method, batch adsorption procedure was applied. Adsorption efficiency was studied as a function of the initial metal concentration, pH of the solution, contact time, and amount of the adsorbent. Optimum removal of copper ions was achieved at pH values of 5.0. About 90% of copper cations were removed in 5 min of contact time from the solution with the lowest copper concentration (50 mg Cu2 +/l) regardless adsorbent amount, while the same effect of adsorption was achieved in 60 min in case of solutions with higher concentrations of copper. It was concluded that the effect of adsorbent amount on adsorption kinetics is evident but not crucial. It was proved that the experimental results of copper adsorption fit well to a Langmuirian type isotherm which was used to describe monitored adsorption phenomena. The calculated adsorption capacities of lignite for copper adsorption decrease with increasing adsorbent amount. The study proved that tested lignite is very efficient adsorbent material, especially in case of low copper concentration in aqueous solution where the usual methods are either economically unrewarding or technically complicated. This behavior can be explained by FTIR spectrum despite a small specific surface area of lignite. Namely, many bands (peaks) are attributed to the functional groups that they are involved in chemisorption and ionic exchange, basic mechanisms of copper adsorption.