Preparation And Study On Photocatalytic And Adsorption Performance Of Titanium-based Oxides

How to deal with ammonia nitrogen pollution algae pollution and heavy metal pollution in water is still the focus of world environmental research.In this paper,the environmentally friendly titanium oxide was used as photocatalyst and adsorbent,and the hollow B-SiO₂@TiO₂ and TiO₂graphite composite photocatalyst were used to catalyze the degradation of ammonia nitrogen and green algae.Also,the adsorption of heavy metal ions in water by nano calcium titanate was studied.The structure-activity relationship between structure and catalytic activity of the photocatalytic degradation of ammonia nitrogen and green algae by nano TiO₂ composite photocatalyst and the kinetic and thermodynamic characteristics of the adsorption of heavy metal ions by nano calcium titanate were studied.The specific research results are as follows.:?1?Hollow B-SiO₂@TiO₂ composites were prepared by the wet chemical deposition method starting from TiCl₄ and hollow B-SiO₂ microspheres.TiO₂ layers composed of anatase TiO₂nanoparticles were coated on the surfaces of the hollow B-SiO₂ microspheres probably through the formation of Ti–O–Si and Ti–O–B bonds.A great number of–OH groups were also present at the TiO₂ coating layers.The presence of Ti–O–Si bonds and Ti–O–B bonds resulted in the formation of defects in the TiO₂ coating layers,which decreased the band gap of the TiO₂ coating layers to ca.3.0 eV and endowed the TiO₂ coating layers with visible light absorption performance.The buoyancy hollow B-SiO₂@TiO₂ composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae.The conversion of ammonia-nitrogen reached65%when the degradation of ammonia-nitrogen?43 mg/L at pH value of 8?was catalyzed by the B–SiO₂@TiO₂?100:10?composite under the simulated solar light irradiation at 35 ^oC for 660 min.The green algae?5 mg/L?were almost completely degraded over the B–SiO@TiO₂?100:20?photocatalyst under the visible light irradiation at 35^oC for 510 min.?2?In this experiment,titanium tetrachloride was used as raw material to support TiO₂ and prepare TiO₂/nano-graphite sheet catalyst.Due to the small supporting capacity of TiO₂,there was no TiO₂ peak in the XRD peak.TiO₂ particles can be clearly seen on the surface of prepared TiO₂/nano-graphite catalyst,with the average size ranging from 0.03?m to 0.04?m.Under the simulated sunlight irradiation,TiO₂/nano-graphite sheet photocatalyst was used to conduct ammonia nitrogen degradation experiment.According to the experimental results,the highest ammonia nitrogen conversion rate was 89%?initial concentration of ammonia nitrogen 50 mg/L,pH=10?after the catalytic degradation of ammonia nitrogen for 300 min at the reaction temperature of 17⁰C by TiO₂/nano-graphite sheet?100:3?composite photocatalyst.The experimental results show that TiO₂/nano-graphite nanophotocatalyst has good photocatalytic performance.?3?Calcium titanate?CaTiO₃?cuboid-like nanoparticles with the average widths and lengths of101–184 and 203–329 nm were hydrothermally synthesized using metatitanic acid and calcium hydroxide as starting materials at 120–180^o C.Metatitanic acid is an intermediate in the commercial TiO₂ pigment production by the sulfuric acid method.High hydrothermal temperature favored the formation of small-sized CaTiO₃ cuboid-like nanoparticles.When the CaTiO₃cuboid-like nanoparticles were used as the absorbents for the removal of heavy metallic cations from aqueous solution,the Langmuir adsorption isotherms showed that the maximum adsorption capacities of the CaTiO₃ cuboid-like nanoparticles for Pb?II?,Cd?II?,Ni?II?,and Co?II?cations were 237.0,74.7,60.8 and 61.2 mg g^-1,respectively.The thermodynamic analysis revealed that the adsorption process of these metallic cations was spontaneous and endothermic.Conclusion:based on the above experiments,it can be seen that B–SiO₂@TiO₂ and TiO₂/graphite composite photocatalyst were successfully prepared and showed good degradation effects on ammonia nitrogen,reaching 75%and 89%respectively,indicating that titanium oxide has a very good degradation capacity for ammonia nitrogen.At the same time,calcium titanate was successfully prepared and adsorbed in heavy metal ions,and it was found that cations of Cd?II?,Pb?II?,Ni?II?and Co?II?have a high adsorption capacity.It can be seen that titanium oxide has a good adsorption performance for heavy metal ions.