Study On The Functionalization Of Mesoporous Silica And Its Adsorption/Degradation Performance Of Antibiotics In Wastewater

Tetracyclines（TCs）antibiotics are widely used in the treatment of human diseases,agriculture,forestry and animal husbandry because of their high practicability and low price.Due to the serious"virtual persistence"of antibiotics on human health and ecological balance,how to find effective treatment methods to remove antibiotics from wastewater has become a frontier and hotspots in research.Antibiotic treatment methods include biochemical,electrochemical,membrane separation,adsorption,catalysis and so on.Among them,adsorption has the advantages of inexpensive,high efficient,recyclable and easy operation.Based on the adsorption,catalysis can further decompose the pollutant molecules and then reduce secondary pollution.This paper focused on mesoporous silica with high specific surface area,large pore volume and controllable and adjustable pore size.Adsorption active species aluminum（Al）was introduced into the mesoporous silica（SiO₂）by improving the synthesis method;Then,catalytic species were introduced into Al-SiO₂ through the grinding-assisted self-infiltration method to further enhance the catalytic ability of the material.After that,the obtained Cu-SiO₂ composites were used in the treatment of antibiotic wastewater.1.Using the traditional hydrothermal method,a series of mesoporous SiO₂adsorbents（named Fx）containing Al were prepared by under the weak acid environment provided by the hydrolysis of AlCl₃·6H₂O in aqueous solution containing template and silicon source.Fx has high specific surface areas(723-876 m²·g^-1)and large pore volume(0.82-1.06 cm³·g^-1).The adsorption of TC followed the pseudo-second-order kinetic model,and F1.0（r Al:Si=1:1）has the highest removal rate for TC(83%,C₀=80 mg·L^-1).Moreover,F1.0 has better TC removal ability than SBA-15,Al₂O₃ and industrial SiO₂.The adsorption of TC on Fx samples can be well fitted by Langmuir isotherm model,showing that the process of adsorbing TC is a monolayer chemical adsorption.Futhermore,the adsorption of TC is dependened by p H values of the reaction solutions.F1.0 has the highest removal rate when p H=5.0(86%,C₀=80mg·L^-1).F1.0 also has 61.8 mg·L^-1 and 62.8 mg·L^-1 adsorption capacity of NOR and CIP(C₀=80 mg·L^-1).At the same time,F1.0 has high recyclability and stability.The material still maintains a good adsorption capacity(73.6%,C₀=80 mg·L^-1)after 6times of adsorption/desorption.Through the influence of p H value and ionic strength on adsorption,it is confirmed that electrostatic interaction is the main mechanism of mesoporous Al-SiO₂ material to remove TC.UV-vis and FT-IR also prove the formation of the surface complexes between TC and F1.0.2.Considering that single adsorption will cause secondary pollution,and the mesoporous SiO₂ still lack active catalytic sites.Therefore,a series of Cu-doped mesoporous C/SiO₂ adsorption/catalyst were synthesized by a simple grinding-assisted self-infiltration method combined with the subsequent in-situ carbonization reduction method.Mesoporous Cu-C/SiO₂ materials have a large specific surface area(653-417m²·g^-1)and pore volume(0.81-0.54 cm³·g^-1);Cu species in the material are mainly Cu（0）compared with a small amount of Cu（I）,and Cu nanoparticles（NPs）are uniformly dispersed in the mesoporous frame.When the dopped Cu species amount is r Cu:Si=0.2:1,the crystal sizes of Cu and Cu₂O NPs in the obtained material Cu-C/SiO₂（0.2）are16.6 nm and 4.2 nm,respectively.The adsorption of TC on Cu-C/SiO₂ material follows the the pseudo-second-order kinetic model,in which Cu-C/SiO₂（0.2）has the highest TC removal rate(86%,C₀=300 mg·L^-1).The Cu-C/SiO₂（0.2）composite has combined adsorption/degradation property for the removal of high concentration TC solution(500mg·L^-1).The removal efficiency reaches 100%within 4 h,and the degradation rate constant was 0.05766.The addition of humic acid（HA）and several cations(Na⁺,Ca²⁺,K⁺)can promote the adsorption of TC on Cu-C/SiO₂（0.2）without reducing the degradation results.Cu-C/SiO₂（0.2）maintain S high total removal capacities of TC（94%,100%）in both tap water and pure water,proving that it can be adapted to a variety of water environments.Further research shows that the carbon,Cu（0）and Cu（I）in Cu-C/SiO₂（0.2）material are all involved in Fenton catalisis,and·OH plays an important role in the catalysis process.Moreover,UV-Vis,FT-IR and XPS all prove the formation of the surface complexes between TC and Cu-C/SiO₂（0.2）material.