Preparation Of Moderately Hydrophobically Modified Organic/inorganic Composite Flocculants And Their Application In The Purification Of Slightly Polluted Water

Rapid urbanization and industrialization have caused serious environmental problems,especially water pollution,which is related to human health and the quality of water environment.In previous studies,emerging pollutants,such as organic micro pollutants and inorganic micro pollutants,seriously polluted the water.The representative of inorganic micro pollutants in water is phosphate and nitrate,while the representative of organic micro pollutants is mainly small molecule drugs such as norfloxacin and diclofenac sodium.Among the above pollutants,more and more attention has been paid to their toxicity and non biodegradability,which has caused great harm to people and other organisms for a long time.Therefore,it is necessary to remove trace inorganic and organic small molecule pollutants in water.Two kinds of moderately hydrophobic modified organic/inorganic composite flocculants were synthesized in this paper,which are:（1）long hydrophobic carbon chain composite metal（iron or titanium）hydroxide（CSF,CST）,and（2）poly（n-propylacrylamide）composite aluminum hydroxide（NSA）.The structure of the product was characterized by Fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscopy and Zeta potential.Then,the application of moderate hydrophobic modified organic/inorganic composite flocculant in surface water containing trace inorganic small molecule pollutants and organic small molecule pollutants was studied by beaker experiment and a small continuous flow flocculation sedimentation device.Finally,the mechanical explanation of flocculation effect was made by X-ray photoelectron spectroscopy,Fourier infrared spectrum and simulation calculation.（1）Long hydrophobic carbon chain composite metal（iron or titanium）hydroxide.The organic/inorganic composite flocculant（CSF,CST）modified by 3-（trimethoxy）propyl-n-octadecyldimethyl ammonium chloride and metal chloride solution showed a good removal effect on macromolecular pollutants such as kaolin,humic acid and small molecular pollutants such as phosphate,nitrate and small molecular drugs.In particular,the removal rate of turbidity,humic acid,nitrate,total phosphorus,sulfamethoxazole and norfloxacin,tyloxacin and diclofenac sodium can reach 80%,90%,75%,91%,80%and 70%respectively.This is mainly attributed to the ability of inorganic polymer components to destroy and capture macromolecular pollutants.Hydrophobic long carbon chain and positively charged quaternary ammonium salt can remove hydrophilic and hydrophobic small molecular pollutants through hydrophobic association and electrostatic neutralization,and remove both small molecular pollutants and particulate pollutants from water at the same time.Compared with traditional commercial flocculants,CSF has high suspended matter removal rate,high flocculant strength and fast sedimentation rate.（2）Poly-N-propylacrylamide composite aluminum hydroxide.Through comparative study,it is found that compared with CSF and CST flocculants,the organic/inorganic composite flocculant（NSA）formed after amidation reaction of polyn-propanylacrylamide and aminosilane coupling agent and then condensation modification with metal chloride solution reduces the amount of flocculant,which reduces the cost to a certain extent.Because there is no quaternary ammonium group in NSA,the nitrate removal rate of NSA is not much different from that of commercial flocculants.NSA has a good removing effect on pollutants in water when the optimal dosage is 40 mg/L,while the optimal dosage of CSF and CST is 120mg/L,which may be caused by the changes in the structure of flocculant caused by different modification methods.The NSA’s purification of water containing small amounts of kaolin,humic acid,phosphate and small molecule drugs has also achieved a better result.The removal rate of turbidity reached 90%,UV₂₅₄reached 98%,phosphate（TP）reached 78%,and four kinds of small molecule pollutants（NOR,SMXL,DCF,TYL）reached 81%,84%,75%,70%,respectively.Compared with the published papers,the number of functional groups of kh-550 was greatly increased after modification.The removal rate of turbidity,norfloxacin,humic acid,phosphate,tylosin,sulfamethoxazole and diclofenac sodium by NSA-10 was improved due to the hydrophobic polymer chain,amino group and aluminum oxide functional groups in the modified organic/inorganic composite flocculant both are relatively high.Through the comparative study of the two systems,it shows that NSA,CSF and CST have obvious advantages as substitutes for traditional commercial flocculants in water treatment.There are organic and inorganic components in NSA,CSF and CST,which overcomes the shortcomings of single flocculant with insufficient charge density.The charge density is greatly increased,and the flocculation window of the composite flocculant is widened and the sedimentation speed is accelerated.In addition,NSA,CSF and CST show a large removal rate for micro organic pollutants in water.Compared with the traditional commercial flocculant,the metal residue in the water after flocculation is smaller,which has no secondary pollution to the environment and avoids the impact of the conventional single flocculant on the environment.