Study On Treatment Of Nitrotoluene Toxic Substances Using Porous Semi-interspersed Thermosensitive Hydrogels Supported NZVI

Nitrotoluene substance belongs to toxic refractory substances and has strong three-way toxicity.It may go into the environment because of safety accidents or improper sewage,and brings biological and human long-term potential harm,causing widespread concern.Due to its stable chemical properties and it's difficult to be biodegradabl.NZVI can reduce nitrotoluene toxic substances to easily biodegradable toluidine substance.However NZVI is easy to deactivate and reunite,preparation of supported NZVI can avoid these problems.But NZVI is easy to deactivate and reunite,preparation of supported NZVI can avoid these problems.In this paper,porous semi-interspersed thermosensitive hydrogels supported NZVI were prepared to treat nitrotoluene toxic harmful substances.Macroporous structure of carriers will favor entry of contaminant molecules.Temperature sensitivity of carriers will favor the control of reduction process and storage stability of supported NZVI.This carrier supported reducing agent can be used for emergency treatment of nitrotoluene toxic substances.Firstly,with N-isopropylacrylamide(NIPAm)as monomer,Polyethylene glycol(PEG)as porogen poly(methylacrylic acid-beta hydroxy ethyl ester)(PHEMA)as second network material,the thermosensitive porous semi-IPN hydrogel carriers with through hole structure and rapid phase transition were prepared by free radical solution polymerization.Effects of different molecular weight porogen PEG,porogen dosage,crosslinker dosage and NIPAm/PHEMA ratio on hydrogels structure and properties were investigated.Structure,microstructure,phase transition temperature,swelling property,specific surface area of gels were characterized by FT-IR,SEM,DSC,BET methods.The results indicated that the vintage preparation conditions are PHEMA/NIPAm=0.25(weight ratio),crosslinker dosage accounting 2.67% of total monomer,PEG molecular weight in 1000~2000.It was found that the pore sizes of the gels prepared under these conditions were about 10 microns and the Specific surface area were about 21m2/g.Swelling equilibrium of gels under room temperature can be reached at 90 minutes,gels of 50?can lose more than 90% of water at 10 minutes.The lower critical solution temperature were about 35.8?.Secondly,using porous semi-interspersed thermosensitive hydrogels of best structure to be carriers to support NZVI with liquid phase in situ reduction NZVI was supported by liquid-pwhase in-situ reduction method,the average weight of supported NZVI was calculated to be 111mg/g from EDS and weighing method.Before swelling gels support NZVI were transparent,after adsorbing Fe3+ they becomed pale yellow,after reducing NZVI gels were black.Comparing SEM micrographs of NZVI-PNIPAm/PHEMA,it shows that NZVI can be successfully supported on the gel carrier,and NZVI particles were evenly dispersed inside the pores,and did not affect the pore structure of the carrier.The size of supported NZVI was about 300 nm.Then with 4-nitrotoluene as the target treatment,effects of the dosage of pH,NZVI-PNIPAm/PHEMA,the initial concentration of 4-nitrotoluene on the treatment efficiency of 4-nitrotoluene were investigated.The optimum treatment conditions that pH=2,mNZVI-PNIPAm/PHEMA=2g,the initial concentration of 60mg/L were determined.Under the optimum treatment conditions,toluene reduction efficiency was 98.52%.Next the kinetics and reaction mechanism of reduction reaction and storage stability and reusability of NZVI-PNIPAm/PHEMA were also discussed.After three months of vacuum drying,efficiency of reduction treatment was still more than 90%,and efficiency of reduction treatment was more than 90% after four times regeneration reuse.At last,using NZVI-PNIPAm/PHEMA to reduce other nitrotoluene materials such as o-nitrotoluene,m-nitrotoluene,dinitrotoluene and trinitrotoluene can achieve better treatment efficiency.