Synthesis of highly efficient porous inorganic polymer microspheres for the adsorptive removal of Pb2+from wastewater

This work reports the preparation of novel porous inorganic polymer microspheres using a suspension dispersion solidification (SDS) method. The porous microspheres exhibit good sphericity with an approximate diameter of 100 μm. With the addition of a foaming agent, the BET surface area of the microspheres increased from 79.80 m2/g to 100.99 m2/g with a corresponding decrease in the pore diameter of up to 7 nm. Batch adsorption experiments were carried out to study the effects of time, dosage, pH, initial concentration and temperature on the measured adsorption capacities. Because of their small particle size and large surface area, the porous inorganic polymer microspheres exhibited outstanding adsorption capacities (629.21 mg/g) for Pb2+with high adsorption rates. Kinetic and isothermal studies revealed that the adsorption data fit well to pseudo-second kinetic, Langmuir and D-R (Dubinin-Redushckevich) models, indicating that both chemical and physical adsorptions, as well as monolayer formation, are occurring in the adsorption process. An investigation of thePb2+distributionof the adsorbent after use revealed thatPb2+diffused into the center of the microspheres, suggesting that low diffusion resistance by the adsorbent and maximum use of the adsorption active sites provide the high adsorption capacity. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic. The used adsorbents could be easily regenerated using an EDTA-2Na solution to give a regeneration ratio of 51% after desorption. The cost-effectiveness, ease of synthesis, and high efficiency of this approach suggest it can be effectively applied for the removal of Pb2+ or other heavy metals on an industrial level.