Preparation and Optimization of the Adsorbent for Phosphorus Removal Using the Response Surface Method

A diatomaceous earth (DE)-based adsorbent DE-Ce was prepared and optimized to remove phosphorus from wastewater. DE was modified through purification–cerium loading, improving its phosphorus adsorption capacity and recycling ability. The preparation conditions were optimized using the Box–Behnken design, and the response surface method was employed to analyze the effects of roasting temperature, cerium concentration, and HCl concentration on the preparation of DE-Ce. Scanning electron microscopy, X-ray fluorescence spectrometry, and X-ray photoelectron spectroscopy were used for characterization, with results indicating that HCl washing can effectively remove impurities. Cerium was mainly loaded onto DE in the form of Ce(OH)3, and pore size and capacity increased following cerium loading, with the formation of a macroporous structure. The obtained DE-Ce adsorbent removed 98.30% phosphorous, with the removal process following the secondary kinetic and Langmuir models. According to material characterization and model analysis results, the phosphorus removal mechanism primarily involves electrostatic adsorption, ligand exchange, and precipitation. Overall, the findings indicate that cerium modification can effectively improve the adsorption capacity of DE.