Preparation Of Poly-silicate-ferric-titanium-chloride And Its Application In Coking Wastewater Treatment

Coagulation process is widely used in wastewater treatment,in which flocculant play an important role.Real-world flocculants have their drawbacks in high dosage and weak organic removal ability,so it is necessary to develop new flocculants for high concentration industrial wastewater treatments.Titanium salts are used in flocculant because of their bio-compatibility and non-toxic coagulation effluent,and it’s high metal valence makes them have excellent coagulation ability.Compound flocculant can combine with the strengths of different types of flocculants to improve thecoagulationperformance.Inthisthesis,a poly-silicate-ferric-titanium-chloride（PSFTC）flocculant was prepared with complex process and its coagulation performance on simulated wastewater,raw water of coking wastewater and biochemical effluent were investigated.The main tasks are as follows:（1）Firstly,the preparation process of PSFTC flocculants was optimized by coagulation of humic acid-kaolin simulated wastewater through a three-factor,five-level orthogonal test.The results showed that the PSFTC with optimized coagulation performance could be got at Fe:Ti of 7:1,alkalinity of 0.8 and（Fe+Ti）:Si of 6:1.The removal rates of turbidity,UV₂₅₄and DOC in humic acid-kaolin simulated wastewater were 99.5%,99.3%and95.9%,indicating that the PSFTC could remove colloidal particles completely matter as well as small part of organic pollutants.For phenol-kaolin simulated wastewater,at a dosage of 30 mg/L PSFTC the removal rate of phenol and turbidity were 4.3%and 96.6%,respectively.FT-IR,XRD and Fe-ferron analyses found that Si-O-Fe and Si-O-Ti bonds existed in PSFTC and the iron in the flocculant was mainly aggregated as amorphous polymers in the states of Fe_band Fe_c.（2）To investigate the actual wastewater treatment effect of PSFTC,it was applied to the coagulation treatment of coking wastewater biochemical effluent.The results showed that the removal rates of turbidity,DOC,COD and UV₂₅₄were 95.7%,24%,46.4%and 36.1%,respectively,when the dosage was 600 mg/L.3D-EEM,GC-MS and XAD-8 resin separation analysis showed that PSFTC exhibited excellent performance on the removal of tyrosine-like aromatic organic pollutants.SEM,FT-IR,particle size dynamic monitoring and sedimentation performance characterization of coagulated flocs revealed that the flocs were tightly structured with well-developed pores leading to optimal sedimentation performance and organic pollutant carrying capacity.（3）In coagulation pretreatment of raw coking wastewater with higher organic concentration,the performance of PSFTC was compared with poly-silicate-titanium-chloride（PSTC）.It was found that with PSFTC the removal rates of turbidity,DOC,COD,and UV₂₅₄could also reach 90.2%,10.1%,10.7%,and 24.1%,respectively,at a dosage of 800 mg/L,while with PSTC the removal rates of turbidity,DOC,COD,and UV₂₅₄were 80.5%,7%,8.7%,and 15.3%,respectively.3D-EEM,GC-MS and XAD-8 resin separation were selected to analyze the water samples before and after coagulation.PSFTC showed better coagulation and removal effect on hydrophobic,long-chain carboxylic acid and humic acid-like organic compounds,and had certain targeted removal effect on biodegradable organic compounds.The characteristics of PSFTC and PSTC flocs were tested by SEM,fractal dimension and settling performance,and it was found that with PSFTC a more developed tighter three-dimensional lattice-like flocs was obtained,and so a better settling performance in the coagulation process could be observed.Due to its excellent coagulation performance on coking wastewater,the as-prepared inorganic compound PSFTC shows the potential applications on the removal of organic pollutants from industry wastewater.