Adsorption And Photocatalytic Properties Of Modified Titanium Oxide And Application

Titanate nanotubes?TNT_s?and titanium dioxide?TiO₂?,as two typical titanic oxides,boast tremendous advantages in adsorption and photocatalysis.It has been demonstrated that TNTs may be prepared simply and have a good adsorbing effect for heavy metal cations,while it may be adversely affected by other ions and organic matters in the practical wastewater treatment.TiO₂ features strong oxidability,non-toxic,low price,environmental protection,complete degradation,etc.in photocatalytic degradation of organic pollutants,however,due to its wide band gap,it cannot make an efficient use of solar energy,besides,the electron-hole pair generated on surface has a high recombination rate,leading to a low quantum efficiency.Defects including the said factors constitute key constraint factors for development of TiO₂.TNTs were modified with Powder Activated Carbon?PAC?using one-step hydrothermal method synthesis to gain the new material TNTs@PAC.TNTs may be attached to the surface of active carbon granules in a way of interweaving morphologically,or partially inlaid inside the pore of activated carbon.Conversely,some active carbon granules may be attached to the surface of TNTs,and the specific surface area may reach654.2m²/g.A study was conducted on the adsorption property and mechanism of materials for heavy metal lead ion(Pb²⁺),cationic dye methylene blue?MB?,anionic dye methyl orange?MO?and zwitter-ion dye Rhodamine B?RhB?in wastewater.The maximum monolayer saturated adsorption capacity of TNTs@PAC for Pb²⁺may reach 318.5mg/g.As the concentration of co-existing ions Na⁺and Ca²⁺changed from 0 to 10mM,the adsorption efficiency of TNTs@PAC only reduced by 5.4%and 15.1%,showing insignificant impact.Humic acid?HA?had a weak impact on the adsorption of TNTs@PAC for Pb²⁺,and this is because that its component PAC may adsorb HA and the combined pollutant of HA-Pb.TNTs@PAC was desorbed for regeneration with EDTA-Na₂,after three times of cycle,its desorption rate?D?was still larger than 93.2%and the adsorption rate?R?was still larger than 91%.Its adsorption mechanism mainly comes from the electrostatic attraction and ion exchange.The maximum monolayer saturated adsorption capacity of TNTs@PAC for MB,RhB and MO was 263.16,149.25and 108.7 mg/L respectively.This indicates that this material has the strongest adsorption for cationic dyes.This material was recycled for 3 times using the photocatalysis of TNTs under UV-irradiation,and this material has a high repeating utilization factor for MB,showing stability in the large;while its utilization factor decreased from 96.5%to 67%for RhB,and declined sharply from 96.4%to 46.7%for MO.This may be correlated with the structure of the dye.TiO₂ loaded on SiO₂ was compounded using sol-gel method and modified with Bi system compound,to obtain the new material Bi/TiO₂/SiO₂.Then,the experimental materials Bi/TiO₂/SiO₂-600 and Bi/TiO₂/SiO₂-800 were prepared by burning Bi/TiO₂/SiO₂under high temperature?600? and 800??.This composite was present morphologically as aggregated nano particles.Prior to calcining,Bi/TiO₂/SiO₂ showed as aggregate with blurred and disperse edges,while SiO₂ and TiO₂ were in amorphous state.After calcining,the crystal structure of TiO₂ emerged gradually,and became visible and observable.Photo-degradation kinetics of modified experimental materials Bi/TiO₂/SiO₂-800 and Bi/TiO₂/SiO₂-600 for three kinds of dyes may be described by L-H model.The ideal fitting data of first-order kinetic equation may contribute to the maximum correlation coefficient R?above 0.99?.According to the reaction rate constant of photocatalysis gained from the model,both of the two materials show MB k₁>RhB k₁>MO k₁.While,Bi/TiO₂/SiO₂-800 has a stronger photocatalysis compared with Bi/TiO₂/SiO₂-600.This may be due to that high temperature can contribute to a better crystallization for adherent TiO₂,besides,more rutiles and anatases are generated,therefore,the mixed crystal may greatly improve the photocatalytic performance of the material,thus,the material may play a more efficient function in catalytic degradation of dye ions.