Effect of calcium ion on the adsorption of dissolved humic acid onto TiO2 particles in water

In order to clarify the role of HA (humic acid)-TiO2 adsorption in the phot ocatalytic process, a series of experiments were performed to investigate t he adsorption mechanisms in the absence or presence of calcium according to the intermolecular interaction force theory. Based on the experimental res ults, the models of adsorption mechanism were designed, which were useful i n explaining the phenomena that happened during adsorption processes. ne ad sorption of humic acid onto the TiO2 particles was desperately pH-dependent ; however, calcium could increase the amount of adsorption, which was mainl y attributed to the calcium ion bridging. The effects of calcium concentrat ion and TiO2 dosage on the adsorption process are also discussed.