High performance adsorbents based on hierarchically porous silica for purifying multicomponent wastewater

Hybrid hierarchically porous silica adsorbents were simply fabricated by the sol-gel method and modified with thiol or sulfonic groups. These materials with pores on both micrometre and nanometre scales exhibit a satisfactorily adsorptive property to various pollutants in water, including heavy metal ions (Hg2+, Cd2+, Pb2+, Cu2+, Ag+ and CrO42-) and organic compounds (dyes, biogenic amines, pesticides and amino acids). The thiol functionalized hierarchically porous silica micro-foam (SH-HSM), which has a low thiol content (0.66 mmol g(-1)), shows significantly high adsorption capability to Hg2+ (140.1 mg g(-1)) in particular. Then sulfonic acid-functionalized adsorbent (SO3H-HSM) was obtained through direct oxidization of SH-HSM by H2O2 without destruction of the hierarchical structure. It was found that SO3H-HSM could effectively remove organic compounds with positive charge in solution through electrostatic interactions. The adsorption capability of SO3H-HSM for some basic dyes, such as fuchsin basic, could reach approximately 1145.2 mg g(-1). The mixture of SH-HSM and SO3H-HSM showed good purifying capacity to simulate multicomponent wastewater, containing different inorganic and organic chemicals. The removal rate for any of the pollutants was more than 90%, and could even reach 100% for metal ions and dyes. The strong adsorption ability of these porous adsorbents may be due to the interwoven meso-and macroporous structures which can increase mass transport and easier accessibility for pollutants to the active sites.