Alkali-modified Ficus benghalensis fruit waste: An effective biosorbent for heavy metal removal from aqueous solutions - A comparative study

Plant-derived biomass is widely recognized as a cost-effective and environmentally friendly option for pollutant removal, as demonstrated in numerous studies. These waste materials are frequently used in bioremediation efforts as alternatives to chemical treatments. In this study, Ficus benghalensis fruit waste powder (FBFWP) was employed as a low-cost biosorbent for the removal of Cr, Ni, and Pb from aqueous solutions. To characterize FBFWP, advanced analytical techniques, including Fourier-transform infrared, powder X-ray diffraction, field emission scanning electron microscope, and BET, were used to analyze its surface properties. Batch experiments were conducted to optimize key parameters such as adsorbent dose, particle size, and pH conditions. In addition, adsorption kinetics and isotherms were evaluated to better understand the adsorption behavior of FBFWP. The kinetic results indicated monolayer adsorption for the FBFWP biosorbent. Removal efficiency decreased with higher initial metal concentrations, likely due to the saturation of available adsorption sites. However, increasing the biosorbent dose improved removal efficiency by providing a larger surface area and more adsorption sites for metal uptake. pH studies revealed that a pH of 5 was optimal for effective binding, facilitating the biosorption of metal ions. The kinetic data closely followed the pseudo-second-order model, with high correlation coefficients near unity for Cr and Pb, indicating chemisorption driven by the adsorption capacity. In contrast, the model was less applicable to Ni (R2 = 0.81). The biosorbent exhibited good reusability for Cr and Pb over two cycles but showed significantly reduced performance for Ni after the first cycle.