Abstract:In this study, acid leaching solution of coal gangue was taken as a raw material to prepare polyaluminum iron titanium chloride (PTAFC), a highly efficient coagulant, through titanium doping, polymerization, curing, concentration and drying process. The effects of preparation conditions of PTAFC (titanium dosage, pH, polymerization temperature, and polymerization time) on turbidity removal were investigated. Besides, the turbidity, COD, TP and NH3-N removal effects from the effluent of secondary sedimentation tank of urban wastewater treatment plant by PTAFC were studied and compared with those by traditional polyaluminum iron chloride (PAFC). The results showed that the prepared PTAFC possessed the best performance under the preparation conditions of Ti-Fe molar ratio of 0.3, pH 1.5, polymerization temperature of 60 ℃, 3 h polymerization and 24 h curing at room temperature. When the coagulation conditions were set as follows: PTAFC dosage of 70 mg·L?1, pH 7, reaction temperature of 20 ℃ and slow stirring speed of 40 r·min?1, the best removal effects of turbidity, COD and UV254 of laboratory-made wastewater occurred with the removal rates of 99.13%, 37.25% and 39.9%, respectively. For the effluent of secondary sedimentation tank of urban wastewater treatment plant, PTAFC had an excellent removal effect on turbidity and total phosphorus, while a certain removal effect on COD and NH3-N, which were significantly better than PAFC. This study is of great significance for effectively reducing the stockpiling of coal gangue and expanding its utilization channel, as well as realizing the low-cost and high-efficiency industrial production and application of coagulant. Key words:coal gangue/ acid leaching/ polyaluminum iron titanium chloride/ turbidity removal rate.
CHENG W P, CHI F H. A study of coagulation mechanisms of polyferric sulfate reacting with humic acid using a fluorescence-quenching method[J]. Water Research, 2002, 36(18): 4583-4591. doi: 10.1016/S0043-1354(02)00189-6
[2]
BELL-AJY K, ABBASZADEGAN M, IBRAHIM E, et al. Conventional and optimized coagulation for NOM removal[J]. American Water Works Association, 2000, 92(10): 44-58. doi: 10.1002/j.1551-8833.2000.tb09023.x
[3]
EDZWALD J K, TOBIASON J E. Enhanced coagulation: US requirements and a broader view[J]. Water Science & Technology, 1999, 40(9): 63-70.
[4]
黄鑫. 聚合钛盐混凝剂的研究[D]. 济南: 山东大学, 2017.
[5]
OKOUR Y, SHON H K, EL S I. Characterisation of titanium tetrachloride and titanium sulfate flocculation in wastewater treatment[J]. Water Science & Technology, 2009, 59(12): 2463.
[6]
ZHAO Y, GAO B Y, SHON H, et al. Floc characteristics of titanium tetrachloride(TiCl4) compared with aluminum and iron salts in humic acid-kaolin synthetic water treatment[J]. Separation and Purification Technology, 2011, 81: 332-338. doi: 10.1016/j.seppur.2011.07.041
[7]
GAO B Y, LIX X, WANG M, et al. The impact of pH on floc structure characteristic of polyferric chloride in a low DOC and high alkalinity surface water treatment[J]. Water Research, 2011, 45(18): 6181-6188. doi: 10.1016/j.watres.2011.09.019
[8]
CHENG W P. Comparison of hydrolysis/coagulation behavior of polymeric and monomeric iron coagulants in humic acid solution[J]. Chemosphere, 2002, 47(9): 963-969. doi: 10.1016/S0045-6535(02)00052-8
CHENG F, CUI L, MILLER J, et al. Aluminum leaching from calcined coal waste using hydrochloric acid solution[J]. Mineral Processing & Extractive Metallurgy Review, 2012, 33(6): 391-403.
CHEKLI L, ERIPRET C, PARK S H, et al. Coagulation performance and floc characteristics of polytitanium tetrachloride (PTC)compared with titanium tetrachloride (TiCl4) and ferric chloride (FeCl3) in algal tubid water[J]. Separation & Purification Technology, 2017, 175: 99-106.
[20]
ZHAO Y X, GAO B Y, CAO B C, et al. Comparison of coagulation behavior and floc characteristics of titanium tetrachloride (TiCl4) and polyaluminum chloride (PACl) with surface water treatment[J]. Chemical Engineering Jounal, 2011, 166(2): 544-550.
GAO B Y, CHU Q Y, YUE B J, et al. Characterization and coagulation of a polyaluminum chloride (PACl) coagulant with high Al13 content[J]. Journal of Environmental Planning and Management, 2005, 76(2): 143-147.
HUANG X, SUN S L, GAO B Y, et al. Coagulation behavior and floc properties of compound bioflocculant-polyaluminum chloride dual-coagulants and polymeric aluminum in low temperature surface water treatment[J]. Journal of Environmental Sciences, 2015, 30(4): 215-222.
[36]
ISTV'AN L. On the type of bond developing between the aluminum and iron(Ⅲ) hydroxide and organic substances[J]. Water Science and Technology, 1993, 27(11): 242-252.
AUVRAY F, VAN HULLEBUSCH E D, DELUCHAT V, et al. Laboratory investigation of the phosphorus removal (SRP and TP) from eutrophic lake water treated with aluminium[J]. Water Research, 2006, 40(14): 2713-2719. doi: 10.1016/j.watres.2006.04.042
Faculty of Geosciences & Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China Received Date: 2020-02-21 Accepted Date: 2020-04-07 Available Online: 2021-01-13 Keywords:coal gangue/ acid leaching/ polyaluminum iron titanium chloride/ turbidity removal rate Abstract:In this study, acid leaching solution of coal gangue was taken as a raw material to prepare polyaluminum iron titanium chloride (PTAFC), a highly efficient coagulant, through titanium doping, polymerization, curing, concentration and drying process. The effects of preparation conditions of PTAFC (titanium dosage, pH, polymerization temperature, and polymerization time) on turbidity removal were investigated. Besides, the turbidity, COD, TP and NH3-N removal effects from the effluent of secondary sedimentation tank of urban wastewater treatment plant by PTAFC were studied and compared with those by traditional polyaluminum iron chloride (PAFC). The results showed that the prepared PTAFC possessed the best performance under the preparation conditions of Ti-Fe molar ratio of 0.3, pH 1.5, polymerization temperature of 60 ℃, 3 h polymerization and 24 h curing at room temperature. When the coagulation conditions were set as follows: PTAFC dosage of 70 mg·L?1, pH 7, reaction temperature of 20 ℃ and slow stirring speed of 40 r·min?1, the best removal effects of turbidity, COD and UV254 of laboratory-made wastewater occurred with the removal rates of 99.13%, 37.25% and 39.9%, respectively. For the effluent of secondary sedimentation tank of urban wastewater treatment plant, PTAFC had an excellent removal effect on turbidity and total phosphorus, while a certain removal effect on COD and NH3-N, which were significantly better than PAFC. This study is of great significance for effectively reducing the stockpiling of coal gangue and expanding its utilization channel, as well as realizing the low-cost and high-efficiency industrial production and application of coagulant.