High efficient removal of tetracycline from solution by degradation and flocculation with nanoscale zerovalent iron

• The long-term process of TC reacted with ZVNI was investigated.
• The 99% removal was obtained when 500 mg/L TC was processed with 0.2 g/L ZVNI.
• The flocculation (69%) is more important than the degradation and adsorption (30%) in removal of TC with ZVNI.
• The degradation process and flocculation was analyzed.

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. 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. Furthermore, the flocculation kinetics was strongly dependent on pH and ionic strength. Neutral environment and high ionic strength can improve efficiently the sedimentation rate. The XPS analysis of flocculation showed that the Fe consisted of mainly Fe(III) and some Fe(II). 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.

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