K2S2O8强化g-C3N4薄膜电极光电催化降解Cu(CN)32-并同步回收Cu

采用高温液相生长法制得g-C_3N_4薄膜电极并作为光阳极,以石墨毡作为阴极,建立了光电催化系统.通过对比光电催化体系、K_2S_2O_8体系以及外加K_2S_2O_8到光电催化体系,发现在光电催化系统下外加K_2S_2O_8可以有效地提高光电催化降解Cu(CN)_3~(2-)的效率,并实现了Cu在阴极上的有效回收.探究了K_2S_2O_8投加量对CN-降解率和Cu回收率的影响,发现当K_2S_2O_8浓度为1 mmol·L~(-1),偏压为1.0 V时,CN-的去除率和Cu回收率分别达到86.23%和82.11%.通过SEM、EDS和XPS分析阴阳极表面形貌,发现部分Cu+被氧化以CuO的形式存在于沉淀和阳极表面,大部分铜离子通过电化学还原作用以单质铜的形式沉积于阴极表面,铜离子有效地从体系中去除.电子顺磁共振及淬灭实验分析表明,CN-的氧化去除是硫酸根自由基(SO·-4)氧化和非自由基氧化共同作用.

Enhanced Photoelectrocatalytic Oxidation of Cu(CN)32- and Synchronous Cathodic Deposition of Cu by Peroxydisulfate

Oxidation of Cu-cyanides by a photoelectrocatalytic method was enhanced by adding peroxydisulfate (PS). In the photoelectrocatalytic system (PEC), graphitic carbon nitride (g-C₃N₄) thin films prepared by a liquid-based reaction and graphitic carbon felt (GCF) were used as the photoanode and cathode, respectively. First, various processes, including PEC, PS oxidation, and PEC with PS addition (PEC/PS), were compared for Cu-cyanide removal. The addition of PS improved greatly the photoelectrocatalytic efficiency for the oxidation of CN^- and the recovery of Cu on the cathode. The effect of the amount of K₂S₂O₈ was investigated in detail. The removal efficiency of CN^- and Cu recovery can reach up to 86.23% and 82.11%, respectively, with 1 mmol·L^-1 K₂S₂O₈ at 1.0 V bias potential. Combined with the SEM, EDS, and XPS analysis of the electrode surface, it was concluded that the free Cu⁺ was oxidized and existed in the precipitation and photoanode in the form of CuO. Conversely, the liberated Cu⁺/Cu²⁺ ions were electrochemically reduced to elemental Cu on the surface of the graphitic carbon felt cathode. As a result, metal Cu was recovered from the wastewater of the copper cyanide complexes. Electron spin resonance and radical quenching experiment analysis showed that the oxidation of CN^- is assigned to sulfate radical oxidation and non-radical oxidation processes.