Removal Of Tetracycline From Waterbody By Iron Based Materials

Tetracyclines (TCs) are used in livestock and poultry breeding, their emissions cause serious harm in the water environment. The removal of tetracycline (TC) with nanoscale zerovalent iron modified by starch (starch-NZVI) was investigated using batch experiments as a function of reactant concentration, pH, time, competitive anions and ionic strength in this paper. The removal efficiency of 99% was obtained,30% which was contributed from the adsorption and degradation and 69% which was attributed to flocculation when 500 mg/L TC was processed with 0.20 g/L starch-NZVI. The TC removal capacity of starch-NZVI increases with increasing the TC concentration, the maximum removal capacity of TC was 4137.3 mg/g when the initial TC concentration is 1000 mg/L. Furthermore, the flocculation kinetics was strongly dependent on pH and ionic strength. Neutral environment and high ionic strength can improve efficiently the sedimentation rate.99% Fe-TC complex colloid could be deposited after 7 d, When the NaCl concentration was higher than 2.0 M, it could be deposited after 24 h.The XPS analysis of flocculation showed that the Fe consisted of 88% Fe(?) and 12% Fe(?). LC-MS analysis revealed that the organic components included TC and the degradation products which resulted from the oxidization effect for TC. Our results firstly demonstrated that the combination degradation with flocculation is an efficient method on TC removal from solution with NZVI.In order to quickly removal of tetracycline from waterbody, we find that the Fe(?) and tetracycline is easy to form a positively charged chelating substances, it can be adsorbed fastly and efficiently by PP composite resin. By studying the material number of O=C-NH-C groups, the content of iron ion and tetracycline, salt ions, combination optimization under the condition of adsorption isotherms, kinetics found Fe(?) can significantly promote the tetracycline by resin adsorption, whereas Fe(?) uptake seldom changed in the copresence of TC. Within 500 min, a large number of tetracycline has been removed. Preliminary discussion on the mechanism is as follows:Fe(?) and TC formed Fe-TC complex first, then by resin adsorption, as the iron bridge, it has a large number of unoccupied molecular orbitals, not only with tetracycline has coordination effect, but also with the amide and O=C-NH-C of PP have coordination effect. The more resin in the O=C-NH-C groups, the effect of removing tetracycline is higher. The interaction between Fe(?)/Fe-TC and carboxyl was probably a kind of ionic exchange, but the carboxylic acid groups and iron ion interaction force is strong, can destroy the Fe-TC complex structure, and form the COO-Fe (?) structure.