Preparation Of Cu₅（OH）₄（PO₄）₂ And Its Photocatalytic Reduction Of Uranium Water

With the rapid development of nuclear power industry in China,uranium mining has been strengthened,uranium production and application have been continuously expanded,and decommissioned nuclear facilities have been continuously treated.Therefore,the amount of radioactive uranium containing wastewater has gradually increased.How to effectively remove low concentration uranium in water is attracting more and more attention.Photocatalysis technology has attracted the attention and research of many scholars at home and abroad because of its non-toxic environmental protection,economic efficiency,good stability and high recovery.Ti O₂ is the most widely used photocatalyst in photocatalytic reaction because of its high availability,chemical stability,low cost and corrosion resistance.However,the band gap energy of Ti O₂ is high（3.2 e V）and can only respond in the ultraviolet region（≤400 nm,accounting for 5%of solar light）,so the utilization rate of solar energy is low.Therefore,seeking suitable photocatalysts,expanding the spectral range of photocatalytic materials and utilizing solar energy efficiently are the frontier directions in the field of photocatalytic reduction of U（Ⅵ）.Cupric hydroxyphosphate（Cu₂（OH）PO₄）is a kind of photocatalysis material with research value and development prospect because of its easy separation of electron hole and wide light response range.However,the electron in Cu₂（OH）PO₄ is transferred by the bridge O in·OH,which leads to the low photocatalytic activity.In order to solve the above problems,the pseudomalachite type copper tetrahydroxyphosphate（Cu₅（OH）₄（PO₄）₂）was selected as the research object.By increasing the proportion of bridge O and introducing more electron transfer channels,the photocatalytic activity was improved;the photocatalytic reduction rate of uranium containing wastewater was further improved by the"amorphization"of microstructure regulation;combined with the related characterization methods,the light was explored The mechanism of Cu₅（OH）₄（PO₄）₂photocatalytic reduction of U（Ⅵ）and the mechanism of amorphous structure improving its photocatalytic activity were discussed.The main conclusions are as follows（1）In this study,pseudomalachite type Cu₅（OH）₄（PO₄）₂ Photocatalyst was prepared by hydrothermal method with Cu（NO₃）₂ and（NH₄）₂HPO₄ as raw materials and polyvinyl pyrrolidone as dispersant.The composition and crystallinity of pseudomalachite type Cu₅（OH）₄（PO₄）₂ are the key factors affecting the photocatalytic performance.The results show that the preparation conditions（ratio,p H value,preparation temperature,preparation time）have different effects on the crystal growth,morphology and photocatalytic performance of the microspheres.The optimal preparation conditions are:m（Cu（NO₃）₂:（NH₄）₂HPO₄）=5.5:1,p H=9.5,preparation temperature T=190℃,preparation time t=18 h.The optimal conditions are as follows:p H=6.0,s=1.25 g/L,photocatalysis time 180 min,the removal rate of U（Ⅵ）is 80.5%,and 76.2%of U（Ⅵ）can still be removed after 5 times of recycling.（2）Amorphous Cu₅（OH）₄（PO₄）₂ was prepared at low temperature.The optimum preparation conditions were obtained as follows:m（Cu（NO₃）₂:（NH₄）₂HPO₄）=4.5:1,p H=9,preparation temperature T=100℃,preparation time t=15 h.The results showed that 96.3%of U（Ⅵ）could be removed from the wastewater containing uranium at p H=6.0,s=1.25 g/L,and photocatalytic time was 120 min.92.3%of U（Ⅵ）could be removed after 5 times of recycling.