Surface Modification Of Fe₃O₄ Nanoparticles For Treatment On Emulsified Oil Wastewater

Oily wastewater not only brings many environmental issues,but also threatens the survival of human society.At present,there are so many defects of common oil-water separation materials,such as huge dosage,difficulty re-collection,the secondary pollution and so on.Therefore,it is urgent to develop an effective,advisable method to separate the oil from aqueous environment.In this paper,we devoted our efforts to the fabrication of chitosan?CS?-based flocculants,aminopropyl-modified nanoparticles and chitosan?QC?-coated magnetic nanoparticles.Detailed studies were conducted on oil-water separation performance and mechanism.The main contents include the following three parts:?1?Chitosan?CS?-based flocculants,denoted as CS-g-PAM and CS-g-PDBC,were successfully prepared via graft copolymerization of CS with acrylamide?AM?or dimethyl acryloyloxyethyl benzyl ammonium chloride?DBC?.It was found that CS-g-PDBC exhibited excellent flocculation performance under both acidic and neutral conditions,while CS showed better flocculation ability under alkaline condition.The flocculation mechanism of CS and CS-g-PDBC was investigated via zeta potential measurements.Results showed that different flocculation mechanisms were involved at various pH levels.As regarding CS,the flocculation mechanism is mainly charge neutralization,patching and sweep floc under acidic,neutral and alkaline conditions,respectively;while for CS-g-PDBC,patching was the dominant mechanism under both acidic and neutral conditions.?2?A series of pH-sensitive magnetic nanomaterials?MNPs?were synthesized and characterized for their evaluation in separation of emulsified oil from aqueous environments.A coprecipitation method was used to produce Fe₃O₄ magnetic nanoparticles that were coated in a 2-step process with first silica to form a surface for anchoring an?3-aminopropyl?triethoxysilane?APTES?molecular layer.Also,characterization methods such as TEM,XRD,FTIR,Zeta potential,VSM were used to prove magnetic nanoparticles successfully preparation.Detailed studies were conducted on effects of MNPs dosage,APTES anchoring density?DA?and pH on oil-water separation performance of the synthetic MNPs.Alkaline conditions allowed the MNPs to be recycled up to 9 cycles without showing any significant decrease in oil-water separation efficiency.An examination of the oil-water separation mechanism found that electrostatic interaction and interfacial activity both played important roles in oil-water separation.Results showed that,under both acidic and neutral conditions,MNPs with high DA exhibited enhanced oil-water separation performance,while under alkaline condition,the oil-water separation process was minimal.?3?A class of novel quaternized chitosan?QC?-coated magnetic nanoparticles?MNPs?was successfully synthesized.The synthesized MNPs were characterized by various technologies such as TEM,XRD,FTIR,Zeta potential and their oil-water separation efficiencies were evaluated in detail.Results showed that Fe₃O₄ and Fe₃O₄@SiO₂ MNPs exhibited negligible oil-water separation effect.After coating with APTES,the oil-water separation efficiency was only improved under acidic condition.However,QC-coated MNPs not only exhibited excellent oil-water separation performance at various pH levels,but also could be reused up to 8 times without showing significant decrease in oil-water separation efficiency.All of these results suggested QC-coated MNP could potentially be a class of promising materials for oil-water separation.An examination of the oil-water separation mechanism found that electrostatic interaction played important roles in oil-water separation.