Generating Electricity,Producing Persulfate And Hydrogen Peroxide Simultaneously From Sulfate Wastewater

Sulfates are the primary components of wastewater discharged from various industries including medical,fertilizer,and chemical,which is a potential contaminant for the aqueous environment and is detrimental to human health.However,the existing wastewater treatment methods are ineffective in utilizing sulfate productively.Because of the catalytic properties of WO₃photoelectrode,we proposed a photocatalytic fuel cell（PFC）based on sulfate radicals converted from sulfates in situ for wastewater treatment and chemical energy utilization.What’s more,we further explored the self-bias photoelectrocatalytic system producing persulphate and hydrogen peroxide by oxidizing sulphate wastewater,for the resourceful use of sulphate wastewater.The main contents of the research are as follows:（1）A novel photocatalytic fuel cell（PFC）is first proposed for the treatment of sulfate-rich organic wastewater,in which sulfates can be converted in situ easily into sulfate radicals to degrade organics in wastewater while generating electricity.The results of the present study show that various model compounds and actual wastewater can be used as substrates in the PFC system.For instance,methyl orange,a typical refractory organic,exhibits excellent electricity generation with a short-circuit current density of 3.72 m A·cm^-2,open-circuit voltage of 1.32 V,and a maximum power-density output of 1.68 m W·cm^-2.Meanwhile,the degradation efficiency of methyl orange reached 74.2%after 4 h in the PFC system.Significant wastewater treatment and chemical energy utilization i s also achieved from the self-bias design of the photoanode,which includes a front photoanode of WO₃ and a rear photocathode of Si photovoltaic cell（Si PVC）,accelerating the charge separation and increasing the electron transfer rate of the PFC cell.Therefore,the proposed PFC system provides great potential for resourceful utilization of sulfate-rich organic wastewater and chemical energy recycling.Furthermore,sulfate radicals dominating the oxidation reaction of the PFC system are confirmed by the free-radical capture reaction.（2）A self-bias photoelectrocatalytic system was proposed to further explore generating persulphate and hydrogen peroxide simultaneously by photoelectrocatalytic.In this system,we used self-bias photoanode to generate persulphate and gas diffusion electrode（GDE）with its porous structure on the surface to generate hydrogen peroxide.The results showed that the concentration of hydrogen peroxide and persulphate were0.75m M·h^-1 and 2.63m M·h^-1respectively when the p H value was 2,the sodium sulfate concentration was 1M,and the gas diffusion electrode was selected.Compared with the traditional preparation method,the PEC system does not require external voltage and chemical substances added.The system also provides a new idea for the resourceful use of sulphate wastewater.