Research progress of modified natural zeolites for removal of typical anions in water

Natural zeolite has been regarded as an adsorbent for cation removal in water. However, natural zeolite cannot effectively adsorb anions due to the negative charge. In recent years, great effort has been put into surface modification of natural zeolite to enhance the anion removal performance. Modification methods and research progress of anionic contaminant removal in water by zeolites were reviewed. The adsorption mechanisms were also generalized to provide useful implications in designing of zeolite adsorbents with excellent performance against anions. In addition, the prospect of natural zeolite application in wastewater treatment was also investigated. The main conclusion drawn was that the composite-modified zeolite exhibited the optimal performance. Tuning the pore size, modifying the pores, and introducing appropriate functional groups into the internal and external structure of zeolites were core to the design and enhancement of zeolite properties. However, attention needs to be paid to the treatment of the adsorbed saturated zeolite to prevent the generation of new pollution sources into the environment.