Conversion and utilization of waste biomass into sustainability treasure: Surface modified eggplant biomass by PEI and enhanced removal of Pb(II) from aqueous solutions

It is imperative to develop innovative methods for transforming natural biomass waste into environmentally benign and cost-effective functional adsorbents for use in the remediation of contaminated water environment. In this work, a polyethyleneimine (PEI) functionalized biomass-based adsorbent (PEI@E-Bio) with a high density of amino groups and rough and expansive surface was synthesized using waste eggplant as the raw material, exhibiting a high removal efficiency and a rapid rate of Pb(II) removal from polluted water. The maximum Pb(II) removal efficiency of 99.36 % was achieved for the optimized run with conditions of pH: 6, temperature: 20 °C, adsorption time: 90 min, PEI@E-Bio dosage: 0.2 g/L, and initial Pb(II) concentration: 10 mg/L. The pseudo-second order kinetic model provides a superior fit to the adsorption data, suggesting that the removal of Pb(II) by the PEI@E-Bio adsorbent occurs via a chemisorption process. Additionally, the influence of microstructure and surface chemistry on Pb(II) adsorption efficiency was also evaluated. The results demonstrated that the plate-like structure was the primary factor influencing the physical adsorption process. Conversely, the abundance of functional amino groups could markedly enhance the impact of chemical adsorption. The negative values of Δ H o and Δ G o demonstrate that the exothermic characteristic of the spontaneous and feasible adsorption process. The PEI@E-Bio has demonstrated robust adsorption stability and efficient regeneration performance in practical applications, highlighting its potential as a feasible, cost-efficient, and sustainable material for removing Pb(II). This research study is centered on the transformation of natural waste into biomass to effectively eliminate pollutants. It establishes a theoretical framework for environmentally conscious waste treatment, resource utilization, and the conversion of waste biomass into advanced materials.