Studies on the treatment of tannery wastewater using low cost natural adsorbents

Abstract

Environmental impact of leather production is considerable. Three major pollutants namely chromium, dye and phenol from the leather process industries are known to cause major concern to the environmentalists. This is due to the significant impact they have on the environment. The currently practiced treatment methods are unsatisfactory and expensive and often have secondary pollution problems with sludge. Hence, there is a need for cost effective and efficient removal technologies. Biosorptive removal of chromium from aqueous solution has been carried out by employing naturally available low cost materials like seaweed (Sargassum wightii, Turbinaria ornata) and Bacillus subtilis microbial biomass. The treatment of protonated biosorbent with aqueous chromium solution at a pH of 3.5-3.8 for duration of 6 h gave the maximum uptake of about 35, 28 and 25 mg/g for protonated S. wightii, T. ornata and B. subtilis, respectively. FT-IR, EDX analysis and flame photometry studies have been carried out to understand the mechanistic pathway for the removal of chromium by the selected biosorbent. Desorption studies carried out indicate the reuse potential of the biosorbent. Calcium alginate beads have been employed as an adsorbent for the removal of anionic and cationic dyes, which are most commonly used in leather industry. Maximum adsorption capacity of 27.5, 25, 12.5 and 57.70 mg/g has been achieved at an initial concentration of 300 mg/L of acid brown, direct blue, acid orange and basic black dye, respectively employing 4 g/L of calcium alginate. Desorption studies have been carried out, which indicate the reuse potential of the alginate beads. Biosorption of basic yellow and basic blue dye onto the Caulerpa scalpelliformis seaweed has been carried out. A maximum uptake of 27 and 33 mg of cationic yellow and cationic blue dye, respectively per gram of seaweed has been observed. The average effective diffusion coefficients have been determined for both the dyes.