Solar Engineering of Wastewater Treatment for Full Mineralization of Organic Pollutants.

Full mineralization of organic pollutants is a tough task by using existing technologies. Even if all conventional energies and extremes are exhausted, high temperature wastewater treatment is not worth the loss from the perspective of energy. Solar engineering holds promise for a goal of the full mineralization of organic pollutants to tackle the global fossil energy shortage. Here, we report a solar engineering for full mineralization and efficient solar utilization. The solar energies and spectrum were fully utilized to initiate the solar heat and solar electricity. Two energies were applied to trigger the thermochemical and electrochemical oxidation of the organic pollutants. Our study bridges the gap between the energy and environment toward efficient solar utilization and effective water treatment. As a proof-of-concept study, we demonstrate a solar engineering of full phenol mineralization in wastewater. A record phenol mineralization rate was achieved to reach an oxidation of rate 98% and COD of 93% under a constant current density of 50mA/cm at 150°C. UV and HPLC were used to detect the intermediates during variable time intervals. The results showed that the intermediate products are composed of maleic acid, hydroquinone and p-benzoquinone. In the extremes of high temperature (90°C), the solar oxidation time and pathway are greatly altered. The reaction rate constant at 150°C is about 11 times than that at 90°C. Application of more solar heat significantly favors to reduce the activated energy of the pollutant oxidation and lower the electrolysis potential.