Fabrication, characterization, and potential application of modified sawdust sorbents for efficient removal of heavy metal ions and anionic dye from aqueous solutions

Abstract

The present research focuses on developing highly efficient, low-cost, and eco-friendly bio-sorbents based on lingo-cellulosic materials in oak wood sawdust waste. Sawdust was chemically modified using poly (amido amine) PAMAM as an active polymer and epichlorohydrin as a cross-linker. The chemical composition and surface morphology of resulting sorbents were investigated before and after immobilization of titanium oxide, TiO2, and zinc oxide, ZnO, nanoparticles onto modified sawdust. The potential application of the bio-sorbents for removing heavy metal ions, including Cu2+, Co2+, Cr6+, Cd2+, and Mn7+, and Alphanol® fast blue acid dye from their aqueous solutions was evaluated. The modified sawdust sample with the highest nitrogen content, SD3, exhibited the best adsorption efficiency. The extent of removal varies by pollutant as: acid dye (100%) ˃Cu2+(99%)˃ Mn7+(98%) ˃ Co2+(95%) ˃ Cr6+(92%) ˃ Cd2+(85%), keeping other parameters constant (adsorbent dose, 1 g L−1; time, 45 min; initial concentration, 100 mg L−1). Immobilization of titanium dioxide and zinc oxide nanoparticles (TiO2 NPs and ZnO NPs) onto SD3 significantly improves pollutant removal. The highest adsorption capacity obtained at equilibrium was 200 mg g−1 for acid dye uptake. Additionally, adsorption of both Cr +6 and acid dye follow pseudo-second order kinetics which suggests that adsorption takes place via chemisorption reactions. Reusability and regeneration of cellulosic adsorbents were also demonstrated. Removal of heavy metal ions and acid dyes from wastewater could be attained using low-cost and highly effective adsorbents. TiO2 and ZnO NP-loaded sorbents exhibited a remarkable adsorption capability and also significantly inhibited the growth of pathogenic microorganisms.