Removing Tetracycline From Water By MWCNT And The Quick Detection Of Tetracycline

With more and more widely use of tetracycline(TC)in animal husbandry breeding and aquatic products,the residue of TC has caused serious harm to the environment.In this paper we choose Multi-walled carbon nanotubes(MWCNT)as sorbent and has systematicly studied TC's adsorption behavior on MWCNT and adsorption mechanism.The best adsorption conditions were found,which provide the theoretical basis for the subsequent online testing tetracycline.The results of the study show that:1.Compared TC adsorption on the different adsorbents.The results show that the bare MWCNT has the best adsorption effect of TC.The best condition for adsorption:in room temperature,adding 8 mg MWCNT,shaking 20 min,the adsorption rate can reach 99%.On the basis of adsorption,3.25 mol/L AICl3 was used to the desorption experiment,the desorption percentage was up to 80%.2.TC adsorption kinetics were found that the equilibrium was reached within 20 min following the pseudo-second-order model with observed rate constants(k2)of 0.0263,0.0306,0.0322 g/mg·min(at varied temperatures).The activation energy of MWCNT was 2.58 kJ/mol.The whole rate process appeared to be influenced by both intraparticle diffusion and boundary layer diffusion.3.The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 269.54 mg/g(293 K)of TC on MWCNT.The mean energy of adsorption was calculated to be 0.0291 kJ/mol(293 K)from the Dubinin—Radushkevich adsorption isotherm,which indicate that the process belongs to physical adsorption.Moreover,the thermodynamic parameters for the adsorption were estimated,and AG?<0,?H?>0,?S?>0 values indicated the endothermic and spontaneous nature of the sorption process.4.Adsorption mechanism:by changing the TC solution pH value,we found that,when the pH of TC solution value was between 4.5-7.0,we got best adsorption effect.The adsorption mechanism is probably the non-electrostatic ?-? dispersion interaction between bulk ? systems on MWCNT surface and TC molecules contained both benzene rings and double bonds(C=C,C=O),or hydrophobic interaction between MWCNT and TC.The variation of Ionic strength has no effect on adsorption rate proves the adsorption mechanism further.5.MWCNT are modified on electrode,0.1 mol/L,pH=3 Citric acid-citric acid sodium was choosed as buffer solution for this experiment,and 0.5 mg/mL,4 ?L SDBS-MWCNT modified electrode made the best effect.Besides,the limit of detection was 3.59×10-7 mol/L,RSD=6.73%.The experimental results show that 1000 times Na+,K+,Mg2+,Ca2+,Zn2+,Fe3+,Cu2+,Pb2+;500 times Al3+,NO3-,NO2-,SO42-,PO43-;100 times Dopamine had no interference on the experiment.The TC residues of environment has been detected by this method.