| Chromium especially hexavalent chromium can poison human skin, respiratory and digestive systems, and can cause cancer,and also is one of five highly toxic heavy metal. Wastewater containing chromium is one of the most serious pollution to environment and one of the most harmful wastewater to human.Although a variety oftemperature; the stir speed was 40~60 r/minchromium-containing wastewater treatment methods have been developed, there are various shortcoming and can’t achieve the desired treatment effect objective.Therefore, the development of new high efficiency of chromium-containing wastewater treatment method is of important practical significance. This study, based on the invention patent "an amphoteric polymeric chelate flocculant and its preparation methods"(ZL200910043653.7), uses chelating precipitation method to treat chromium-containing wastewater, and amplifies the scale zoom to 10 L test,successful synthesis of amphoteric chelating polymer flocculant and its application in chrome tanning and chrome plating wastewater treatment.( 1) PDMAMDTC was synthesized by using dimethyldiallylammonium chloride(DMDAAC), acrylamide(AM), formaldehyde(HCHO), triethylene tetramine(TETA), carbon disulfide(CS2) and sodium hydroxide(Na OH) as raw materials, and according to the 10 L scale of amphoteric chelating polymer flocculant(PDMAMDTC) was synthesized successfully, the suitable synthetic conditions for PDMAMDTC were determined, perfect, optimized the process parameters:â‘ The appropriate synthetic conditions for PDMAM were as follows:a. The ratio of monomer was n(DMDAAC) ∶n(AM)=(0.40~0.45)∶1, the dosage of initiator to monomer was 1.1% ~ 1.1% of total quality;b. Reaction conditions : in nitrogen gas atmosphere 30 min; Reaction temperature and time, respectively : reaction time 2~3 h and temperature 55~60 ℃ at the first stage, and reaction time 0.5 h and temperature 65 ℃ at the second stage.â‘¡ The appropriate synthetic conditions for PDMAM-g-TETA are as follows:a. n(AM)∶n(HCHO) ∶n(TETA)=1∶0.9~0.95∶1.1~1.2b. The appropriate range of p H value was 10.3-10.7c. Reaction temperature and time, respectively: reaction time 40~50 min and temperature 45~50 ℃at the first stage, and reaction time 1.5~2 h and temperature50~55 ℃ at the second stage.â‘¢ The appropriate synthetic conditions for PDMAMDTC were as follows:a. The mass percent concentration of PDMAM)-g-TETA was 4%~5%;b. The ratio of n(TETA)∶n(CS2)∶n(Na OH)=1∶2.5~2.8∶3.25~ 3.64;c. Reaction temperature and time, respectively: reaction time 3~4 h and room temperature at the first stage, and reaction time 1.5~2 h and temperature 50~55 ℃ at the second stage.( 2) This chapter synthesis of amphoteric chelating polymer flocculant PDMAMDTC for drugs, system study the PDMAMDTC chrome tanning wastewater removal effect. After laboratory test and 1 m3 expansion test in the field, determine chrome tanning wastewater treatment process, perfect, optimized the process parameters:â‘ In hexavalent chromium reduction process: the dosage of copperas was80~82 g/m3; the reaction time was 30~35 min; the reaction temperature was at room â‘¡ In chelate reaction process: the p H value was 7.00~10.00; the dosage of PDMAMDTC was 40~42.5 L/m3; the stir speed was 60~100 r/min; reaction time15~20 minâ‘¢ The flocculation precipitation process: the mass percent concentration of PAM was 0.5‰,and treating chrome tanning wastwater the dosage of PAM was 1.5~2L/m3; the stir speed was 40~60 r/min; stir time 5~10min; deposition time was 20~30min.After processing its total chromium and hexavalent chromium can reach leather and fur processing industrial water pollutant discharge standard(GB 30486-2013).COD can reach secondary standard of integrated wastewater discharge standard(GB8978-88). And compared with Na OH, disulfide generation of sodium formate and commercially available heavy metal capture agent DTC, heavy metal icon adsorbent RTC, PDMAMDTC treatment effect was good.(3)PDMAMDTC on effect of chromium plating wastewater treatment were systematically studied, then determine the process flow and main technical parameters:â‘ In chromium plating wastewater use Na HSO3 as reductant can reduction hexavalent chromium effectively, when the dosage of Na HSO3 was 1.4 times of theoretical value, hexavalent chromium was restored basically. The best dosage of Na HSO3 was 689.5 mg/L, reduction reaction time was 10 min, temperature was at home temperature.â‘¡ In chromium plating wastewater treatment the p H value should be controlled in 6.7 ~ 8.5; the dosage of PDMAMDTC was 7.6~8 m L.When the chromium plating wastewate initial COD was 476 mg/L, the total chromium was 238.2 mg/L,the hexavalent chromium was 163.4 mg/L,the p H value was 2.03, the removal rate of total chromium and COD were 99.60% å'Œ 94.44%,meanwhile, the residual turbidity were 1.7 NTU, the indicators of COD and total chromium all below the Emission standard of Pollutants for Electroplating(GB21900-2008); the floc thick and dense, sedimentation speed.In summary, in order to synthesis of amphoteric polymer chelated flocculant PDMAMDTC chrome tanning wastewater treatment and chrome plating wastewater containing chromium, such as wastewater, good treatment effect, simple process, easy operation control;PDMAMDTC both strong chelating chromium ion ability and excellent flocculation performance, it is a good plating chromium waste water treatment agent.This study for the effective governance of chromium-containing waste water provides a feasible way, has a broad application and dissemination value. |
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