Optimization of boron adsorption from desalinated seawater onto UiO-66-NH2/GO composite adsorbent using response surface methodology

Abstract

The removal of boron in desalinated seawater has always been one of the keys to restrict the use of desalinated seawater. For this reason, a composite adsorbent named UiO-66-NH2/GO was successfully prepared by a simple solvothermal method through this research. It is composed of graphene oxide and water-stable metal organic framework UiO-66-NH2, and for the first time as a boron adsorbent for the treatment of desalinated seawater. Various technologies were applied to systematically analyze the stability, structure, topography and chemical characteristics of the composite adsorbent. The relationship between the influencing factors and the adsorption effect was investigated, including the amount of adsorbent, contact time, initial concentration of boron, and pH of the boron solution. It is proved that the boron adsorption complies the pseudo-second-order kinetic model, the intra-particle diffusion model and the Langmuir isotherm model through the fitting of experimental results. The adsorption of boron by UiO-66-NH2/GO has both physical and chemical adsorption, including electrostatic attraction, covalent bond or electron transfer. The results of thermodynamic study pointed out the adsorption of boron is spontaneous and feasible. The response surface method was designed to improve the adsorption conditions of boron. The optimized adsorption conditions to reach 26.45 mg/g of boron adsorption were found to be at dosage of 75.03 mg/g with pH of 5 and temperature of 321.19 k. UiO-66-NH2/GO showed good removal ability for low concentration boron and good reusability. The above suggest that UiO-66-NH2/GO has the potential to be applied to desalinated seawater treatment.