1. College of Environmental Science and Engineering, Guilin University of Technology, Guilin 541006, China; 2. Key Laboratory of Guangxi Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin 541006, China; 3. Collaborative Innovation Center for Water Pollution Control and Water Security in Karst Areas, Guilin 541006, China; 4. Key Laboratory of Drinking Water Science and Technology, Research Center for Eco Environmental Sciences, Chinese Academy of Sciences, Beijing 100035, China
Abstract：The biochar-based nano palladium-copper bimetallic catalysts (Nano-PdCu-BC) were prepared by wet chemical- immersion reduction method aiming to break through the current technical bottleneck of efficient treatment of nitrate pollution in water. The influences of catalyst preparation precursor concentration, initial nitrate concentration, current intensity, catalyst dosage and initial pH value on electrocatalytic reduction of NO3-N were investigated in this study. The results showed that the palladium copper bimetal could be successfully loaded on the biochar of bamboo by impregnation and reduction, and the Nano-PdCu-BC bimetal catalyst could be obtained. Under the conditions that the precursor solution is 0.60g/L PdCl2 and 0.15g/L CuCl2, the initial NO3-N concentration is 100mg/L, the current intensity is 220mA, the initial pH value is 7, and the catalyst dosage is 0.80g/L, the removal rate of NO3-N reached 99.68%, and the selectivity of N2 was about 44.25% after 180min. The reaction of Nano-PdCu-BC electrocatalytic reduction of NO3-N conforms to the first-order kinetics with a kinetics constant k-value of 0.034/min. After three cycles of reuse, the removal rate of NO3-N remains above 95%, and the selectivity of N2 remains above 40%. Moreover, the mechanism of electrocatalytic reduction of nitrate by Nano-PdCu-BC bimetallic catalyst was revealed. After adsorption of NO3-N by nano-zero-valent Cu, it was oxidized to CuO, which provided electrons to promote the reduction of NO3-N to NO2-N, and then in synergy with nano-zero-valent Pd to indirectly reduce NO3-N by activating atomic hydrogen (H*) for adsorption, achieving the purpose of reducing NO3-N to NH4or N2.
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