Selective Pollutants Removal And Complex Wastewater Purification By Microfludically-generated Functionalized Biosorbents

With the social imbalanced progress and economic rapid development,a large amount of untreated and partially treated wastewater containing highly toxic organic pollutants and refractory heavy metal contaminants from the agriculture,industry and energy sectors,etc.,was directly discharged into aquatic environments,having caused severe water pollution.In this context,this study is aimed at achieving the complex wastewater deep purification and targeted pollutants selective adsorption by using nexw nanomaterials.In this study,polymethyl methacrylate(PMMA)microfluidic chip was designed and fabricated by combining laser engraving and thermocompression bonding technologies.On this basis,microfluidical droplets in-situ observation system was built to realize the online morphology observation and size measure of the microdroplets.Also.microfluidic parallel magnification system was established to achieve the integrated mass production of adsorbent microspheres from preparation,crosslinking to final functionalization.In addition,based on the observed multistage microdroplet formation process(including necking,shearing and spheroidizing stages).the stable preparation of chitosan microdroplets in the controllable size range(911.3 ?m?1522.5 ?m)can be easily achieved by adjusting the weight content of chitosan in dispersed phase,or varying the flow rate ratio of dispersed phase to continuous phase.Based on the natural biomass chitosan as raw materials,three kinds of chitosan-based adsorption microspheres(including chitosan microspheres,ion imprinted chitosan microspheres and polyethyleneimine(PEI)grafted chitosan microspheres)were synthesized by combining microfluidic microdroplet preparation technology,ion imprinting technology and/or functional groups surface modification technology,and used for the adsorption study of heavy metal ions(represented by copper(Cu)ions).The results showed that the above three microspheres exhibited excellent monodisperse properties(Dav= 378 ?m?430 ?m,CV<2.7%)and outstanding adsorption properties(qm=75.52 mg g-1?145.92 mg g-1).Adsorption kinetics and isothermal adsorption studies indicated that the adsorption process of Cu ions on chitosan-based microspheres was a complex three-stage process dominated by chemisisorption process.supported by physical diffusion.Also,as-prepared three adsorption microspheres displayed good mechanical strength(0.26 MPa?0.348 MPa),acceptable regeneration property(71.2%?92.3%)and outstanding selective adsorption characteristics for targeted Cu ions.Subsequently,the selective adsorption mechanism of chitosan-based adsorption microspheres for targeted Cu ions was revealed qualitatively and quantitatively by utilizing ionic scale effect inherent electronegativity of heavy metal elements and density functional theory(DFT)analysis.Eventually,based on the inverse emulsion method and two-step crosslinking process,amphiphilic carboxymethyl chitosan/gelatin composite microspheres(CCGMs),with high specific surface area and hierachical porous structure,were developed for highly efficient pH-induced selective removal of anionic methyl orange(MO)and/or cationic methylene blue(MB)(representatives of azo-dyes)from binary mixture.The maximum adsorbance of CCGMs for MO and MB were 383.142 mg g-1 and 584.795 mg g-1,respectively.The newly developed CCGMs could be a highly promising candidate for dyestuff wastewater treatment.