Removal of heavy metals from mining effluents in tile and electroplating industries using honeydew peel activated carbon: A microstructure and techno-economic analysis

This study aimed to optimise the preparation of honeydew peel activated carbon (adsorbent) (HDP-AC) for removing heavy metal ions (Cr3+ and Zn2+ ions) from mining effluents in tile and electroplating industries. The potential of HDP-AC for industrial application was evaluated on the basis of technoeconomic analysis. Two types of HDP-AC were prepared with 10%, 20% and 30% of H2SO4 (HDP-ACS) and H3PO4 (HDP-ACP). The carbonisation process was conducted at a temperature between 430 degrees C and 510 degrees C. The properties of HDP-ACs were investigated using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), lignocellulosic and thermogravimetric analysis, specific surface area analysis, Boehm titration analysis, ash content analysis and iodine number (IN) analysis. Results revealed that highly efficient HDP-ACS and HDP-ACP were prepared with 20% of acid at a temperature between 470 degrees C and 490 degrees C. HDP-ACS and HDP-ACP contained 5.98% vs. 7.93% ash and 1.63 vs. 2.50 m mol g(-1) acidity. pH(pzh) was 4 vs. 3.5, IN was 528.60 vs. 1174.19 mg g(-1) and S-BET was 591.92 vs. 1272.38 m(2) g(-1) for both adsorbents. HDP-ACS exhibited 83.49% and 88.88% of Cr3+ and Zn2+ adsorption efficiency, whilst HDP-ACP had 81.55% and 84.13%. The adsorption capacity (Q(max)) was 834.94 mg Cr3+ and 326.19 mg Zn2+ per gram of HDP-ACS. On the contrary, HDP-ACP had 888.85 mg Cr3+ and 336.51 mg Zn2+ g(-1) of Q(max). The specific cost of HDP-AC was USD 261.81/tonne, which was lower than the commercial market price of USD 1000/tonne. Therefore, the prepared HDP-AC was economically feasible. (C) 2019 Elsevier Ltd. All rights reserved.