Synthesis Of A Novel Series Of Magnetic Composite Flocculants And Their Application In Purification

Flocculant is one of the most commonly used agents in the process of water treatment.And it has a wide variety of applications.The mechanism of flocculation removal of suspended particles in water mainly includes adsorption and charge neutralization,electrostatic cluster,adsorption bridging and net sweeping.Suspended particles in the water first to gradually form a larger floc under the action of the flocculation,then the floc formed is separated from the water in the subsequent flotation or sedimentation process to achieve the purpose of water purification.The efficiency of purification is closely related to the performance of the flocculants.In fact,in order to improve the purification effect,two kinds of flocculants are often added in the process.With the development of material science and technology,organic-inorganic composite materials continue to bring forth the new through the old.Some special functional material can be combined with traditional flocculant to form a complex flocculant with special functions,then the flocculation performance is not affected simultaneously.In this study,a kind of environmentally friendly PAM based composite magnetic flocculant is prepared with nano Fe₃O₄ particles as magnetic materials,and its structure and properties are characterized;The flocculation effect and flocculation mechanism of various kinds of magnetic composite flocculants are studied by coagulation experiments;Based on the fractal theory,the fractal dimension of flocs formed by various flocculants is studied,the relationship between the fractal characteristics of flocs and coagulation effect is revealed,and a mathematical model is established.Fe₃O₄ has a stable crystal structure and strong ferromagnetism.The surface of nano Fe₃O₄ particles is firstly modified by oil acid,and then a series of magnetic composite flocculant are prepared by aqueous solution polymerization of these particles and monomers?AM,DMDAAC,AMPS?in organic-inorganic dual initiator system.That is,CMF1,CMF2 and CMF3 of cationic magnetic composite flocculant,AMF1,AMF2 and AMF3 of anionic magnetic composite flocculant and ACMF1,ACMF2 and ACMF3 of amphoteric magnetic composite flocculant.The structure and properties of the magnetic composite flocculants are characterized by means of FTIR,TG,XRD,SEM,EDX,particle size analysis,magnetic susceptibility,intrinsic viscosity and zeta potential,etc.The results show that Fe₃O₄ is successfully introduced into the molecular chain of composite flocculants,the composite flocculants has magnetic properties.Under the action of the external magnetic field,this characteristic is beneficial to shorten the time of floc separating from water,thereby reducing the volume of subsequent flocculation flotation tank or sedimentation tank,reducing the area,and reducing the investment and operation cost.With the change of comonomer types,magnetic composite flocculants have obvious electrical properties.By adjusting the proportion of monomers,a kind of amphoteric magnetic composite flocculant ACMF2 whose number of negative charges in its molecular chain is equal to the number of positive charges,is prepared.The prepared magnetic composite flocculants have good thermal stability,water solubility,smaller particle sizes,uniform dispersion and high molecular weight.Through the analysis of the thermo gravimetric curve,it is determined that the CMF series of magnetic composite flocculants and ACMF1,ACMF3 are the graft copolymers.There are so many heterocyclic molecules that to be used in conjunction with other flocculants.The AMF series magnetic composite flocculants and ACMF2 are block copolymers.Their molecules are linear,so they can be used alone.The CMF series of magnetic composite flocculants,AMF series magnetic composite flocculants and ACMF2 are respectively used in the kaolin simulated wastewater,Fe?OH?3 colloid solution simulated wastewater and bentonite simulated wastewater,and systematically coagulation experimental studies are conducted in this paper.The effects of dosage,pH,stirring speed and stirring time on flocculation performance are investigated in detail.The mechanism of flocculation is determined combined with the zeta potential and the morphological characteristics of the floc formed after coagulation.The results show that except CMF3,the flocculants have good flocculation performance,more than 90% high removal of turbidity or total iron content has been achieved under the optimum experimental condition,and some even reached more than 99%.Floc particles are large and massive,and easy to separated from water.With the increase of GT value,the flocculation process of AMF3 has experienced a complex process of floc formation,fragmentation,reagglomeration and refragmentation.The coagulation mechanism of CMF1,AMF2 and ACMF2 is mainly electrostatic cluster and magnetic agglomeration,accompanied by adsorption bridging and net sweeping.The coagulation mechanism of CMF2,AMF1 and AMF3 is mainly adsorption and charge neutralization and magnetic agglomeration,accompanied by adsorption bridging and net sweeping.The coagulation mechanism of CMF3 is mainly adsorption and charge neutralization and magnetic agglomeration,and there is a certain degree of adsorption bridging effect,but there is no net sweeping.Among them,the magnetic agglomeration is the unique mechanism of this kind of flocculants,and it is the supplement to the complex coagulation mechanism.Based on the graphic analysis technique,two-dimensional fractal dimension of the floc formed in coagulation has been drawn out through the statistical calculation.The fractal dimension of flocs formed in the optimum coagulation conditions are highly close to 2,indicating this kind of floc formating closely under the comprehensive action of the electrostatic,magnetic coupling and Fan Dehua gravitational forces,and has fractal characteristics of self similarity and scale invariant.According to the experimental correlation between the fractal dimension and the removal rate obtained under various conditions,a mathematical model of ??? is established.And the statistical analyses of the changes and effects of various factors on the mathematical model of the ? value and ?value are carried out in order to judge the performance of flocculants and coagulation effect by a new way.