An investigation of arsenic adsoorption using zeolites improved surface properties by doping iron and aluminum oxides

Nowadays, the world is facing water crisis due to lacking of clean drinking water. With the fast development of various industries, a huge quantity of wastewater has been produced from industrial processes and was discharged into water systems. Wastewater usually contains many pollutants such as metalloids, benzene, naphthalene, sulfonates, heavy metals which have poisonous and toxic effects on ecosystems. Removal of these contaminants requires cost effective technologies. Many processes have been developed for the removal of heavy metal ions from aqueous media, including chemical precipitation, coagulation, complexions, ion exchange, solvent extraction, biological methods and adsorption. Currently, adsorption and ion exchange is believed to be a simple and effective technique for water and wastewater treatment and the success of the technique largely depends on the development of an efficient adsorbent. Natural zeolites are hydrated aluminosilicate minerals of a porous structure with valuable physicochemical properties, such as cation exchange, molecular sieving, catalysis and sorption. Natural zeolite and its modified forms have also been reported for removal of anions and organics from water systems. Modifiying zeolites with metal oxides have gained importance in recent years. Nanosized metal oxides, improved for water treatment, Fe3O4 (magnetite), γ-Fe2O3 (maghemite), Fe(III) and Fe(II) oxide groups, Al (oxy)hydroxides (AlOOH) show high performance due to their properties. Magnetic separation technique has been shown to be a very promising method due to their extremely small size and high surface-area-to volume ratio and providing better kinetics for the adsorption. Magnetically activated adsorbents are excellent candidates for combining metal binding, selective adsorption properties. Strong oxidizing power of the holes, redox selectivity, high photo-stability, easy preparation and high affinity -especially to arsenic- make metallic oxides good candidate for environmental remediation. Furthermore; Al(oxy)hydroxides are ubiquitous in nature and reactive, have high specific surface area and charge density, and the resultant high surface reactivity. The association of these oxides, higher binding affinity of Fe (hydr)oxides, the higher stability of Al (oxy)hydroxides, can be an advantageous alternative for removing arsenic from aqueous solution. In the present study, natural zeolite was modified with metal oxide particles and arsenic removal capacities of hybrıd adsorbents were investigated. For this reason the study include following sections: (i) the immobilization of the synthesized metal (oxy)hydroxides on zeolite (ii) characterization of the synthesized adsorbents (iii) evaluation of adsorption potential of natural and modified zeolites, (iv) examination the influence of process parameters and modelling experimental design (v) regeneration studies.