Porous Materials Prepared by Magnesium Phosphate Cement for the Effective Immobilization of Lead Ions

Lead is a toxic heavy metal and is non-biodegradable, often causes soil pollution, and how to fix the soil is a major environmental issue currently facing. The porous material used as lead adsorption materials is one way to solve this problem. In this study, porous adsorption materials were prepared using magnesium phosphate cement (MPC) as a matrix. Their adsorption properties concerning lead ions were studied to understand its fixation ability of lead ions better. The obtained porous materials were characterized by the Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetry (TG) techniques. Batch experiments were conducted to evaluate the effects of leaching time, initial concentration of lead ion solution, and temperature on the prepared materials' performance. The results showed that the pore size distribution of the porous materials based on magnesium phosphate cement (PMMPC) was mainly constituted of mesopores of 4-10 nm. At the same time, the specific surface area was 16.841 m(2)/g. The PMMPC exhibited an excellent adsorption performance for lead ions at 298 K, with a maximum adsorption capacity of 208.233 mg/g. The fitting results of the kinetic and isothermal adsorption equations demonstrated that the adsorption of lead ions by PMMPC followed a pseudo-second-order kinetic and Langmuir model, indicating the occurrence of chemisorption. Within the experimental temperature (298-318 K) and initial concentration (100-250 mg/L) range, the adsorption of Pb2+ on PMMPC was spontaneous owing to the negative values of Delta G. Therefore, PMMPC is a highly effective adsorbent for removing lead ions from aqueous solutions and has vast application potential in wastewater treatment.