Preparation Of TiO₂-SH/molecular Imprinted Polymer In Water And Its Research Of Selective Adsorption And Photodegradation Of 2,4-dinitrophenol

In recent years,as priority pollutants,phenolic compounds have concerned global concerns.Especially,2,4-Dinitrophenol?2,4-DNP?,as one important dinitrophenol forms,has attracted worldwide concerns due to its toxicity,refractory and only partly biodegradability.Seeking for highly efficient methods to remove phenols is of great importance.Titanium dioxide?TiO₂?,as one most popular wide band gap photocatalyst,is widely used in environmental purification du e to its strong oxidization ability,low cost,non-toxicity,and no second pollution.Especially,under UV irradiation,TiO₂ can generate superoxide free radicals?i.e.,O₂^-,HOO^-and OH^-?,thus,exhibits strong oxidation power and completely mineralize ma jority of the organics into CO₂,H₂O and inorganics.However,owing to wide band gap,low utilization of visible-light,poor selectivity,TiO₂ can't specific recognize and selectively remove highly toxic pollutants in mixing solutions,leading to restricted application and development in wastewater treatment.Importantly,in the past three decades,molecular imprinting technology?MIT?has attracted worldwide concerns due to predetermination,specific recognition,practicability.Regarding as one research hotspot,the novel combination of TiO₂photocatalysis and MIT can not only efficiently photodegrade pollutants but also can selectively detect and specifically remove targets.Simultaneously,along with the development of MIP direction from lipophilic substances to hydrophilic molecules,water-compatible molecularly imprinting polymers?CMIPs?in aqueous media have gradually become one hot research trend.Differently,traditional MIPs are commonly formed in organic solvents and used in removal of contam inates in water,however,recognition cavities may be slightly destroyed and changed in the transfer of organic solvent to water.Compared to MIPs formed in organic solvents,CMIPs not only can avoid the possible destroy,but also efficiently reduce the use of organic solvents and responding environmental damage.In this research,a surface molecularly imprinted thiol-functionalized activated TiO₂ photocatalyst?CMIP-coated TiO₂?was successfully prepared in water for selective adsorption and efficient photodegradation of 2,4-DNP in aqueous solution.The main contents are summarized as follows:?1?The molecular imprinting polymers were prepared useing activated TiO₂-SH as support material,2,4-DNP as template molecule,OPDA as functional monomer and cross-linker,MPTMS as silane coupling agent,ammonium peroxydisulfate?APS?as initiator.Then,the obtained particles were washed,signed as CMIP-coated TiO₂.Simultaneously,non-molecular imprinted materials?CNIP-coated TiO₂?were prepared following the identical procedure in the absence of2,4-DNP.The as-synthesized materials were characterized by FESEM,BET,FTIR,UV-vis DRS,XRD,and Zeta-potential.And the results showed that the molecularly imprinted layer was successfully marked on the surface of TiO ₂.?2?Moreover,the prepared CMIP and CNIP-coated TiO₂ were applied to study of the adsorption of 2,4-DNP.Results showed that the average value of adsorption capacity of CMIP-coated TiO₂ was nearly 7.16 mg g^-1,about 1.59 times as many as that(4.51 mg g^-1)of CNIP-coated TiO₂ when pH was 5.0,adsorption time was 20 min,initial concentration of 2,4-DNP was 15 mg L^-1.Additionally,selective adsorption capacity of CMIP-coated TiO₂ for 2,4-DNP was evaluated by comparing the adsorption of CMIP and CNIP-coated TiO₂ for 2,4-DNP and 4-NP in mixed solution.And the selectivity coefficients CMIP and CNIP-coated TiO₂ were 5.8278 and 4.6983,indicating the great selectivity of CMIP-coated TiO₂ for 2,4-DNP.?3?The adsorption kinetics and adsorption isotherm were adopted to investigate the adsorption process of CMIP and CNIP-coated TiO₂ for 2,4-DNP.And the results showed that Langmuir isotherm model was found to better fit to the adsorption equilibrium of 2,4-DNP on CMIP and CNIP-coated TiO₂,indicating adsorption process was monolayer adsorption and binding sites was uniform distributed.Moreover,we have also investigated the adsorption intensity?R_L?further.And the calculated R_L values of CMIP and CNIP-coated TiO₂ at different initial 2,4-DNP concentration were lied in the range of 0¹,confirming that adsorption over the photocatalysts both were favorable.?4?The prepared CMIP and CNIP-coated TiO₂ were studied for photocadegradtion for 2,4-DNP.Results showed that the photocatalytic degradation rate for 2,4-DNP of CMIP and CNIP-coated TiO₂ were 55.61%and 35.68%,respectively,when the pH was 5.0,catalytic reaction time was 120 min and initial concentration of 2,4-DNP initial concentration was 15 mg L^-1.And the results showed that CMIP-coated TiO₂ exhibited great photodegradation performance.And catalytic kinetic was found to better obey the pseudo-first-order kinetic model.Moreover,the influence of experimental parameters such as pH value and initial concentration of 2,4-DNP on the degradation of 2,4-DNP was investigated and analyzed.?5?Moreover,the reusability of CMIP-coated TiO₂ was investigated.And results exhibited that the removal efficiency of 2,4-DNP on CMIP-coated TiO₂ has decreased slightly from 74.62%to 63.26%after five cycles,indicating that prepared CMIP-coated TiO₂ owns great reusability and can be potentially reused in the wastewater treatment.