Efficient phosphate recovery and treatment of high-phosphorus wastewater using sodium alginate-immobilized microspheres based on aluminum-rich water treatment plant sludge.

In recent years, the enhancement of resource utilization for water treatment plant sludge has emerged as a significant global concern. This study utilized aluminum-rich water treatment plant sludge and applied the sodium alginate crosslinking solidification method to produce Microspheres based on water treatment plant sludge (MS-WTPS). The study investigated their properties as an adsorbent material and their effectiveness in treating high-phosphorus wastewater. The resultant material exhibited a porous structure with an elevated specific surface area of 119.35 m g⁻, and it demonstrated exceptional phosphate adsorption capabilities, showcasing a maximum adsorption capacity of 27.69 mg g⁻, which surpassies reported literature values for analogous adsorbents. Furthermore, the adsorption process maintained stability, displaying low sensitivity to pH fluctuations and resilience against interference from coexisting ions. In the complex environment of the actual wastewater, MS-WTPS achieved a phosphate removal rate of 91.02%, and was not easily dispersed and lost by water flow, which makes it easy to be recycled. Utilizing microscopic structural analysis, adsorption kinetics, and pre- and post-adsorption XPS analysis, it is hypothesized that the adsorption of phosphate ions by MS-WTPS is mainly through electrostatic gravitational interaction, ligand exchange and Al-P complexes formation. These works furnish essential technical and theoretical groundwork for the pragmatic implementation of MS-WTPS in high-phosphate wastewater remediation.