Preparation Of Poly-silicate-titanium-ferric-zinc And Its Flocculation Performance Of Azo Dyes And Humic Acid In Water

With the accelerated development of urbanization and industrialization,various pollutants are discharged in large quantities and water pollution is increasing.Among them,dyes and humic acids are two typical organic pollutants in environmental water bodies.They are not only difficult to degrade but also the main source of chromaticity in water,and have persistent damage to the water environment.Therefore,how to efficiently remove these two pollutants has important research significance.Flocculation,as a common water treatment process,can economically and efficiently reduce the chromaticity in sewage and remove pollutants such as organic matter.Flocculant is the core of flocculation technology,which not only affects the water treatment effect but also determines the treatment process cost.In this paper,sodium silicate（Na₂Si O₃·9H₂O）,titanium sulfate（Ti（SO₄）₂）,ferric sulfate（Fe₂（SO₄）₃）and zinc sulfate（Zn SO₄·7H₂O）are used as raw materials to optimize the preparation of inorganic polymer composite flocculant poly-silicate-titanium-ferric-zinc（PTFSZ）for the first time,and it is used to treat azo dye wastewater and humic acid wastewater.The main research contents and conclusions are as follows:1)Preparation of PTFSZThe preparation conditions of PTFSZ are gradually optimized by single factor,orthogonal and response surface experiments with Congo red and humic acid as treatment objects,and two kinds of flocculant PTFSZ1 and PTFSZ2 with different preparation conditions were obtained.The optimum preparation conditions of PTFSZ1are as follows:n（Si）:n（Ti）:n（Fe）:n（Zn）=1:0.61:1:0.33,polymerization p H is 5,and polymerization time is 1.23h.Among them,n（Si）:n（Ti）,n（Si）:n（Zn）and polymerization time have significant effects on the removal rate of Congo red.The interaction between n（Si）:n（Ti）and n（Si）:n（Zn）,the interaction between n（Si）:n（Ti）and polymerization time are significant,while the interaction between n（Si）:n（Zn）and polymerization time is not significant.The optimum preparation conditions of PTFSZ2 are as follows:n（Si）:n（Ti）:n（Fe）:n（Zn）=1:0.53:0.6:0.8,polymerization p H is 4.87,and polymerization time is 2h.Among them,n（Si）:n（Fe）have a very significant effect on the removal rate of humic acid,and n（Si）:n（Ti）and polymerization p H have a significant effect on the removal rate of humic acid.The interaction between n（Si）:n（Ti）and n（Si）:n（Fe）,the interaction between polymerization p H and n（Si）:n（Fe）are significant,while the interaction between n（Si）:n（Ti）and polymerization p H is not significant.2)Characterization of PTFSZThe microstructure,chemical composition and structure of PTFSZ are analyzed by scanning electron microscopy,energy dispersive spectrdmete and fourier transform infrared spectroscopy.The results show that The network structure is formed on the surface of PTFSZ,and the rod-like particles are interlaced and superimposed layer by layer,with a high degree of polymerization and enhanced adsorption bridging ability.Titanium,ferric and zinc have been successfully introduced into PTFSZ flocculant molecules.Ti⁴⁺,Fe³⁺and Zn²⁺are connected with Si through-OH or-O-to form chemical bonds such as Fe-OH、Ti-OH、Zn-OH Si-O-Zn and Si-O-Fe.The PTFSZ flocculant is an inorganic polymer composite flocculant.3)Flocculation performance of PTFSZ on pollutantsPTFSZ1 is used to treat Congo red dye wastewater and Direct Black 22 dye wastewater,and PTFSZ2 is used to treat humic acid wastewater,and the flocculation conditions of PTFSZ on each pollutant was optimized.The optimum flocculation conditions for the removal of Congo red by PTFSZ1 are as follows:PTFSZ1 dosage is0.175mmol/L,initial p H of the water sample is 7.17.First stir at a speed of 190 r/min for 6min,and then slowly stir at 40 r/min for 35min,and the standing time is 90min.Under this condition,the removal rate of Congo red at an initial concentration of50mg/L is as high as 99.14%.The optimum flocculation conditions for the removal of direct black by PTFSZ1 are as follows:PTFSZ1 dosage is 0.13mmol/L,initial p H of the water sample is 7.14～7.46.First stir at a speed of 186r/min for 3min,and then slowly stir at 45r/min for 35min,and the standing time is 75min.Under this condition,the removal rate of direct black at an initial concentration of 50mg/L is 98.63%.The optimum flocculation conditions for humic acid simulated wastewater with p H of 8.36and initial concentration of 20mg/L are as follows:PTFSZ2 dosage is 0.6mmol/L,180r/min fast stirring for 5min,66r/min slow stirring for 22.15min,standing for 120min,humic acid removal rate was 97.58%.4)Effect of coexisting substances on flocculation performance of PTFSZDirect black 22 and humic acid are added to Congo red dye wastewater.Chlorides（Na Cl,KCl,NH₄Cl,Ca Cl₂,Mg Cl₂,Al Cl₃）,sodium salts（Na H₂PO₄,Na NO₃,Na NO₂,Na HCO₃,Na₂CO₃,Na₂SO₄）and substance causing turbidity are introduced into Congo red,direct black and humic acid simulated water samples.The results show that direct black has a certain promoting effect on the removal of Congo red,and PTFSZ1 has excellent removal effect on mixed azo dye wastewater.Humic acid has a significant promoting effect on the removal of Congo red by PTFSZ1.The monovalent cations Na⁺,K⁺and NH₄⁺have little effect on the removal of three pollutants by PTFSZ flocculation.The divalent cations Ca²⁺and Mg²⁺have little effect on Congo red and humic acid,and have a greater impact on direct black.The trivalent cation Al³⁺has a greater impact on the removal of the three pollutants.Low concentrations of Mg²⁺and Al³⁺promoted the removal of humic acid.Common anions Cl^-,NO₃^-and SO₄^2-have little effect on the removal of Congo red and direct black by PTFSZ.Cl^-promoted the removal of humic acid,while CO₃^2-and H₂PO₄^-inhibited the removal of three pollutants.Turbidity promoted the removal of three pollutants by PTFSZ.5)Floc characterization and Zeta potential of water samplesThe flocs of the contaminated substances treated under optimal flocculation conditions are analyzed by scanning electron microscopy,and the fractal dimension of the flocs and the zeta potential of the supernatant after treatment with different flocculant concentrations are analyzed.The results show that the flocs of pollutants are irregular network structure,with the ability of net capture and sweeping,and the flocs adhered to each other.The flocs have good compactness and good sedimentation.The larger the fractal dimension,the smaller the floc gap,the better the sedimentation performance,and the higher the pollutant removal rate.There is a positive correlation between the fractal dimension of the floc and the pollutant removal rate.The positive charge of the flocculant and the negative charge of the waste water solution are electrically neutralized.The absolute value of the Zeta potential is close to 0,the pollutant removal rate is the largest.The charge neutralization plays a leading role,adsorption bridging and net sweeping play an auxiliary role...