The use of low cost zeolites for the removal of selected contaminants and combination with biological process for wastewater treatment

Abstract

Two types of low cost zeolites, namely natural mordenite and synthetic zeolite Y synthesized from a local agro-wastes, rice husk ash were applied to remove various types of contaminants from water. Zeolite Y was synthesized under hydrothermal conditions with appropriate seeding and aging methods, in which the overall relative composition of Na2O: Al2O3: SiO2: H2O is 5.1: 1.0: 10.5: 184.0. The physico-chemical properties of the zeolites were characterized using various techniques. Ammonium removal studies were carried out with the raw mordenite and as-synthesized zeolite Y. Pseudo first order kinetic model and pseudo second order kinetic model were employed to understand the sorption kinetics, while several isotherm equations such as Langmuir, Freundlich and Temkin to study the sorption behavior. To bombard against oxyanions such as nitrate, sulfate and phosphate, the surface chemistry of the zeolites were altered by a cationic surfactant, quaternary amine HDTMA-Br in proportional to the external cation exchange capacity of the zeolites. Both the surfactant-modified zeolites (SMZ) presented significant affinity and adsorption capacity towards the oxyanions. Besides that, while the unmodified zeolites had no affinity towards anionic organic, Acid Orange 7 (AO7), the SMZ showed impressively high adsorption capacity with a rapid removal rate. Suitable kinetics and isotherms models were employed to further understand the sorption behaviors. Combination of the adsorption and biological treatment process in wastewater treatment is interesting. Prior to the study of the combined process, the powdered zeolites and its modified form were first fabricated to the small round particle; several studies were carried out to study the physico-chemical characteristics of the zeolite particles. Indigenous bacteria strains were isolated from a wastewater source and the performance of the bacteria to remove different contaminants was screened. Finally the use of zeolite particle in textile wastewater treatment together with the mixed cultures of bacteria was studied in several approaches.