Abstract

Some trace pollutants exist extensively in the water, soil and other environment, as a result of unorganized emissions. The natural mineral CaCO3 is also widely found in these environments. In this study, we studied the effect of CaCO3 on the transformation of pollutants in water under light and the inactivation of bacteria in different environments. The photolysis of tetracycline (TC) under sunlight in the presence of CaCO3 can be as high as about 77%, which was improved comparing with the pure photolysis under sunlight (15%) and adsorption (32%). The same trend was found when the natural minerals containing CaCO3 (e.g. shell, oyster shell, limestone and marble) were adopted. It was determined that 1.10×10−5 mmol L−1 of ∙OH can be produced under Xenon lamp light source (HID) illumination after 2 h of reaction, which was increased to 4.28×10−5 mmol L−1 in the HID system with addition of CaCO3. According to the calculation by projector-enhanced wave (PAW) method, it was found that the O-H bond length was increased after H2O adsorption on CaCO3. The O-H bond cleavage was easier for more ∙OH generation under light illumination. Based on ZEMAX software simulations, CaCO3 can act as light scatterer and increase the residence time of light in solution.

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