ZnO nanoparticles coated rice husk bio adsorbent for the removal of arsenic, phosphate and fluoride from contaminated water samples

A novel and cost effective bio adsorbent is developed for the removal of As (V), phosphate (PO₄^3-) and fluoride (F-) from water samples by using ZnO nanoparticles coated waste rice husk powder. ZnO nano particles used in this work are synthesized from rotten sweet potato pulp through Chemical precipitation method. The use of rice husk waste as an adsorption support is the key finding and novelty of this work. Integration of ZnO nano with rice husk not only provides high surface area for adsorption but also increase the adsorption rate. The batch adsorption study of the developed bio adsorbent was systematically carried out through the effect of pH, contact time, initial adsorbate concentrations etc. The developed bio adsorbent showed high removal efficiency with a minimum dosage of adsorbent (2 g L⁻¹) and 180 minutes of contact time. The sorption equilibrium data fitted to Langmuir and Freundlich isotherm and kinetic model was studied by nonlinear curve fitting. The sorption equilibrium well to Langmuir (R² = 0.9975) isotherm for arsenic, Freundlich isotherm for both phosphate (R²= 0. 88257) and fluoride (R²= 0.91887). The maximum adsorption capacity is 28.23 mg/g for arsenic, 7.928 mg/g for phosphate and 23.01 mg/g for fluoride obtained from nonlinear curve fitting model. The 100 % removal of As (III) from real contaminated water sample signifies that the developed bio adsorbent will be an excellent opportunity for the removal of toxins from contaminated ground water. The developed bio adsorbent’s working principle is explained through a simple mechanism, highlighting a novel approach in this work.