New eco-friendly FeS-modified biochar derived from peanut shells and walnut shells: a green synthesis approach for removal of lead

The study aimed at firstly preparing two eco-friendly biomaterials of PFeS&PEB and PFeS&WAB from peanut shells biochar (PEB) and walnut shells biochar (WAB) by loading with ferrous sulfide powder (Powder-FeS) to evaluate the ability to remove Pb(II) from sewage. FeS was immobilized to the surfaces biochar through functional groups such as -OH, -COOH and C-O. The results of batch experiments showed that PFeS&PEB had the maximum adsorption capacity (98.039 mg center dot g-1) when pH = 5 and the dosage was 0.75 g center dot L-1. The adsorption data were adequately simulated with adsorption kinetics and isothermal thermodynamic analysis, suggesting that the adsorption of Pb(II) by PFeS&PEB and PFeS&WAB was mainly monolayer chemisorption, and the adsorption process was spontaneous endothermic. The removal of Pb(II) was achieved by the association of complexation, redox, ion exchange, electrostatic attraction and physical adsorption. Reusability studies showed that PFeS&PEB and PFeS&WAB had good stability over four consecutive cycles. Hence, the cost-effective materials of PFeS&PEB and PFeS&WAB can be used as effective bio-adsorbent for the removal Pb(II) from wastewater.