Nanophotocatalytic treatment of seawater using TiO2 immobilized and suspension system under solar irradiation

Organic fouling in desalination plants is a crucial phenomenon resulting in the deterioration of nanofiltration/reverse osmosis filtration performance of membranes and salt-rejection characteristics. In this research, the ef-ficiency of TiO2-suspension and TiO2-immobilized photocatalysis to pretreat seawater under natural solar irradiation has been investigated. The solar nanophotocatalytic performance was evaluated in terms of chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency from feed seawater. Modelling and optimization study was performed in TiO2 suspension system to determine the effect and optimum settings of input parameters such as pH of seawater, reaction time, TiO2 dosage, initial TOC of seawater, and airflow rate into the photoreactor. In a full factorial design, the photocatalytic efficiency of TiO2 nano-thin film immobilized on borosilicate glass tubes was assessed in terms of methanol-TiO2 ratio, nitric acid -TiO2 ratio and solar irradiation time. The optimum removal efficiency of TOC and COD removal in the immobilized system was determined as 51.98% and 57.25%, respectively, at the input factor setting: methanol-TiO2 ratio = 15: 1, nitric acid-TiO2 ratio = 6:1 and solar irradiation time = 120 min. The optimum organic degradation in suspension system was found to be: TOC removal = 73.47% and COD removal = 65.48%.