生物碳基纳米钯铜催化剂的优化制备及脱硝研究

Preparation of biochar-based palladium-copper nano-catalysts and optimization of denitrification performance

针对目前高效处理水体硝酸盐污染的技术瓶颈,以毛竹生物碳为载体基材,通过湿化学-浸渍还原的手段制备生物碳基纳米钯铜双金属催化剂(Nano-PdCu-BC),并以其为粒子电极,协同传统的二维电化学反应器,搭建三维粒子电催化反应体系去除水体中的硝酸盐污染物.探究了催化剂制备的前驱液浓度、初始硝酸盐氮浓度、电流强度、催化剂投加量和初始pH值对电催化还原NO_(3)-N的影响.结果显示,通过浸渍还原的方法可以将钯铜双金属成功负载在毛竹生物碳载体上,获得纳米钯铜双金属催化剂.在前驱液为0.60g/LPdCl_(2)和0.15g/LCuCl_(2)的溶液组合,初始硝酸盐氮(NO_(3)-N)浓度为100mg/L、电流强度为220mA、初始pH值为7,催化剂投加量为0.80g/L的条件下,反应180min后硝酸盐氮去除率可达99.68%,N_(2)选择性约为44.25%;Nano-PdCu-BC电催化还原NO_(3)-N的反应符合一级反应动力学,反应动力学常数k值为0.034/min;经3次循环使用后,NO_(3)-N去除率仍维持在95%以上,N_(2)选择性保持在40%以上;揭示了纳米钯铜双金属催化剂电催化还原硝酸盐的机理,纳米零价Cu位点吸附NO_(3)-N后被氧化为CuO,提供电子促进NO_(3)-N还原为NO_(2)-N,协同纳米零价Pd,通过为吸附激活原子氢H*间接还原NO_(3)-N,达到将NO_(3)-N还原为NH_4和N_(2)的目的.

The biochar-based nano palladium-copper bimetallic catalysts(Nano-PdCu-BC)were prepared by wet chemicalimmersion 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 NO_(3)-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 PdCl_(2) and 0.15g/L CuCl_(2),the initial NO_(3)-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 NO_(3)-N reached 99.68%,and the selectivity of N2 was about 44.25%after 180min.The reaction of Nano-PdCu-BC electrocatalytic reduction of NO_(3)-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 NO_(3)-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 NO_(3)-N by nano-zero-valent Cu,it was oxidized to CuO,which provided electrons to promote the reduction of NO_(3)-N to NO_(2)-N,and then in synergy with nano-zero-valent Pd to indirectly reduce NO_(3)-N by activating atomic hydrogen(H*)for adsorption,achieving the purpose of reducing NO_(3)-N to NH4 or N2.