Effect of cations Ca2+ and Mg2+ on the removal efficiency of humic acid by UV/TiO2

Humic acid (HA) is released from degradation of plant and animal components. Humic substances contribute to chlorination as precursors of disinfection by-products. This study was conducted to investigate the effect of cations Ca2+ and Mg2+ on the removal efficiency of humic acid by the titanium dioxide nanoparticle (UV/TiO2). In this quasi-experimental study, the effect of different variables such as pH, contact time, various concentrations of TiO2, Ca2+, and Mg2+ on the removal efficiency of humic acid by the UV/TiO2 on synthetic water and raw water of Zayandehroud in Isfahan was studied. The results obtained were analyzed using Pearson correlation coefficient test and SPSS software. Optimal concentration of the TiO2 catalyst for removal of HA was 1g/L. The removal efficiency was the highest in acidic conditions (pH=3) within 60 minutes of contact time. The removal efficiency of HA by the UV/TiO2 decreased with increase of contact time. The presence of Ca2+ and Mg2+ ions increased the rate of HA removal by the UV/TiO2. TiO2 photocatalytic process results in a significant reduction in humic materials in water. If water or wastewater contains a high amount of resistant compounds and hardness, these compounds can be broken by a preliminary photocatalytic catharsis and transform to degradable by-products.