Removal of Cr(VI) from wastewater by impregnated activated carbon generated from vegetable tanned leather waste with aluminium oxide

The elimination of Cr(VI) from wastewater was examined by aluminium oxide-doped activated carbon originating from tannery solid waste. Activated carbon was generated from tannery solid waste at 500 °C and aluminium oxide-modified activated carbon composite was prepared at 400 °C in the muffle furnace. The AC-Al2O3 composite was characterized by elemental analysis, spectroscopically and morphologically. It was used as an adsorbent for the eradication of Cr(VI) from wastewater. The FT-IR spectra of AC-Al2O3 show the presence of different functional groups. A porous structure was found in the adsorbents by SEM analysis which was topped up with the chromium ions after adsorption. The maximum removal percentage by AC-Al2O3 adsorbent was found 97.90% at 60 mg/L while the highest adsorption capacity of Cr(VI) was 19.3 mg/g. The EDX analysis results of adsorbent after adsorption indicate the presence of chromium. The BET surface area, average pore size diameter and pore volume of the Al2O3-AC were observed to be 23.26 m2/g, 56.65 Å and 0.0329 cc/g respectively. The adsorption isotherm study revealed that the Freundlich model was best fitted with the regression coefficient (R2) of 0.9913. The kinetic investigation illustrated that the chromium removal process maintained a pseudo-second-order kinetic with the R2 value of 0.9951. Thermodynamic evaluation demonstrated that the adsorption of chromium on AC-Al2O3 adsorbent was spontaneous and exothermic. The study established that AC- Al2O3 is an inexpensive, environmentally friendly, and efficient adsorbent for extracting Cr(VI) from an aqueous solution.