4.2.5. Leather industry waste
The feasibility of leather industry solid waste was evaluated as an adsorbent for removal of Cr(VI) and As(V) from aqueous media. The high amounts of Cr(VI)-133 mg/g and As(V)26 mg/g adsorbed demonstrated the great potential for using this solid waste from the leather industry as a low-cost alternative to the traditionally used adsorbent materials. Fleshing from animal hides/skins, another waste from leather industry, is high in protein content. Raw fleshing has been complexed with iron and is used for the removal of chromium(VI). Iron treatment greatly improved adsorption of the fleshing for hexavalent chromium. The ultimate adsorption capacity of iron treated fleshing was 51 mg of chromium(VI) per gram of fleshing. The sorption capacity of untreated fleshing was 9 mg/g indicating that iron treatment significantly increased the adsorption capacity of fleshing. The adsorption kinetics was well described by pseudo-second-order kinetic model. X-ray photoelectron spectroscopic (XPS) studies showed that the iron was incorporated into the protein matrix. Shifts in XPS spectra suggested that dichromate binding occurred with iron at active adsorption sites and that iron treated fleshing removed chromium(VI) without reducing it to chromium(III).
Sekaran et al. used buffing dust, waste generated from leather industry, for the removal of dyes. The adsorption capacity of buffing dust was found to be 6.24 mg/g at pH 3.5 and 30 ◦C for acid brown dye. The removal of methylene blue from aqueous solutions by adsorption on tanned solid wastes was studied by Tahiri et al.. The maximum adsorption capacity was found ca. 84 mg of methylene blue for each gram of buffing dust.