Removal of Zn²⁺ from Aqueous Solution Using Biomass Ash and Its Modified Product as Biosorbent

To study the removal effect of bottom ash of biomass power plants and its modified products on zinc (Zn²⁺) in aqueous solution, a series of indoor experiments is carried out. The aim of this work is to explore a method to improve the ability of biomass ash to remove Zn²⁺ from aqueous solution and obtain its adsorption characteristics of Zn²⁺ in aqueous solution; on this basis, the feasibility of its application in the treatment of Zn²⁺-contaminated wastewater is analyzed. The mesoporous siliceous material is used to modify the biomass, and the modified material is functionalized with 3-aminopropyltriethoxysilane. The results show that the specific surface area of modified biomass ash is nine times that of the material before modification. The adsorption capacity of Zn²⁺ on the material increases with the increase of pH, and pH 6 is the optimum pH to remove Zn²⁺ from the aqueous solution. The Langmuir model and Freundlich model can show better fits for biomass ash and the modified material, respectively. Thermodynamic analysis results show that the adsorption of Zn²⁺ is spontaneous and endothermic in nature. The adsorption of Zn²⁺ onto biomass and modified biomass ash follow pseudo-first-order and pseudo-second-order kinetics, respectively.