以雪硅钙石为晶种回收废水中磷及其再利用研究
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摘要
磷,对于所有的生命形式都是不可缺少的营养元素,是一种不可再生、不可替代的资源,也是造成水体富营养化的重要元素。合成雪硅钙石具有不含重金属和磷,自身能提供OH~-和Ca~(2+)等优点,并可极大地促进磷酸盐的结晶沉淀,所以合成雪硅钙石是一种污水磷回收的理想晶种。同时,磷肥对农作物的增产起着重要作用。世界上84%-90%的磷矿用于生产各种磷肥,是工业上磷肥生产的主要原料。磷矿资源匮乏且不可再生,而磷矿主要是氟磷灰石[Ca_(10)(PO_4)_6F_2],极难溶于水,容易造成氟的污染。因此将来的发展趋势已不仅仅是去除污水中的磷,而且对污水中的磷还要进行回收再利用,从而降低磷矿开采量,提高磷矿使用年限。
利用合成雪硅钙石回收磷的反应在24小时基本达到平衡。通过热力学计算得到磷回收过程的△G﹤0,△S值为正值,△H﹥0,表明结晶过程为吸热反应,吸附结晶过程是有利进行的;动力学分析表明,速率常数随着温度的升高而增大,反应级数随温度的升高而减小。
课题组前期实验得出的合成雪硅钙石回收磷的优化条件为:pH=8、Ca/P=2(摩尔比)、晶种用量2~2.4g/L、振荡速度140r/min。在此优化条件下,改进回收方法,加大晶种和模拟废水的用量。经55次重复回收磷实验,回收效果稳定,除磷率可达82%。55次回收磷后所得产物的含磷量高达35.02%,已符合富磷矿标准,可以作为冷冻法制取硝酸磷肥的原料。通过XRD、FTIR、SEM和EDS的方法对回收产物进行表征,证明回收的磷主要以结晶度不高的羟基磷灰石的形态存在。对养猪场实际废水进行磷回收实验,在钙磷摩尔比为2,pH值为8,晶种浓度为12g/L的优化条件下,雪硅钙石对实际废水中无机磷的回收率达89.08%。实验结果说明合成雪硅钙石对实际废水中的磷也有较好的回收效果。
冷冻法制取硝酸磷肥的酸解探索实验中,HNO_3浓度低并不影响酸解后溶出磷的量,且在室温下静置较短时间就可以溶出较多的磷。探索实验结果表明室温下用55%的HNO_3静置2h可溶出98.28%的磷;室温下用40.6%的HNO_3静置1h也可溶出95.23%的磷。说明以雪硅钙石回收磷容易被再利用。通过进一步实验研究,得到酸解阶段的优化条件为HNO_3浓度为55%,用量为理论值的290%,酸解时间为2h;而冷冻结晶阶段的优化条件为冷冻结晶时间在6～8h,冷冻温度为-5℃。
Phosphorus is not only an indispensable nutrient element for all the living forms, a nonrenewable and irreplaceable resource, but also an important factor which causes eutrophication of water bodies. Synthetic tobermorite contains neither heavy metals nor phosphorus and can giving out OH~- and Ca~(2+) itself, and also it can promote the crystallization of phosphate. So, Synthetic tobermorite is an ideal seed for the phosphorus recovery from wastewater. Meanwhile, phosphorus fertilizer can increase the production of the crop. 84%-90% of the phosphorite in the world is used for producing every kind of phosphorus fertilizer, so phosphorite is the main material for producing phosphorus fertilizer in industry. We are short of phosphorus and it can not renewable. Moreover, Ca_(10)(PO_4)_6F_2 is the main component in phosphorite and it is hard to dissolve in water, and also it will cause the pollution of fluorine. Thus, in order to reduce the amount of the exploitation of phosphorus and prolong the time we could use phosphorus, now what we should do is not only to recover phosphorus from wastewater, but also we should find a good way to recycle it.
The reaction of recovering phosphorus from wastewater by synthetic tobermorite can reach the equilibrium at about 24h. Thermodynamic study shows that△G﹤0, the value of△S is positive and△H﹥0 during the process of phosphorus recovery. These parameters demonstrate that the process of crystallization is endothermic and the phosphorus adsorption and crystallization by synthetic tobermorite as seed are favorable. Kinetics study shows that the rate constant increases with the increase of temperature, the reaction order decreases with the increase of temperature.
Our research group have got the optimized conditions of phosphorus recovery by synthetic tobermorite, those are pH=8, Ca/P=2 (molar ratio), seed contents 2～2.4g/L, surge speed 140r/min. Based on those optimized conditions, this research increases the amount of the seed and the wastewater. After repeat the recovery experiment for 55 times, the rate of dephosphorization is 82% and the production contains 35.02% phosphorus. This production is already can be the raw material for the phosphorus nitrate production as the high quality phosphorite. XRD、FTIR、SEM and EDS have been employed in testing recovery seed, the results showed that the main recovered product was hydroxyapatite with lower crystallization degree. The results of recovering phosphorus from the wastewater from hoggery show that when pH=8, Ca/P=2 (molar ratio), seed contents 12g/L, the rate of dephosphorization can reach 89.08%. So, synthetic tobermorite has a good quality for the phosphorus recovery from real wastewater.
The experiment of producing phosphorus nitrate by refrigeration shows that low concentration of HNO_3 will not infect the amount of phosphorus which is dissolved by HNO_3. And HNO_3 can dissolve most of the phosphorus within a short time under the room temperature. The result shows that under the room temperature, 55% HNO_3 can dissolve 98.28% phosphorus by reacting for 2 hours; 40.6% HNO_3 can dissolve 95.23% phosphorus by reacting for 1hour. All the results demonstrate that the phosphorus which is recovered by synthetic tobermorite can be easily recycled. After more research, the optimized conditions for dissolving by HNO_3 are the concentration of HNO_3 is 55%, the dosage of HNO_3 is 290% compare to the theoretic dosage, and the time for reaction is 2 hours. And the optimized conditions for the refrigeration process are the time for freezing is 6 to 8 hours, and the temperature should be -5℃.
利用合成雪硅钙石回收磷的反应在24小时基本达到平衡。通过热力学计算得到磷回收过程的△G﹤0,△S值为正值,△H﹥0,表明结晶过程为吸热反应,吸附结晶过程是有利进行的;动力学分析表明,速率常数随着温度的升高而增大,反应级数随温度的升高而减小。
课题组前期实验得出的合成雪硅钙石回收磷的优化条件为:pH=8、Ca/P=2(摩尔比)、晶种用量2~2.4g/L、振荡速度140r/min。在此优化条件下,改进回收方法,加大晶种和模拟废水的用量。经55次重复回收磷实验,回收效果稳定,除磷率可达82%。55次回收磷后所得产物的含磷量高达35.02%,已符合富磷矿标准,可以作为冷冻法制取硝酸磷肥的原料。通过XRD、FTIR、SEM和EDS的方法对回收产物进行表征,证明回收的磷主要以结晶度不高的羟基磷灰石的形态存在。对养猪场实际废水进行磷回收实验,在钙磷摩尔比为2,pH值为8,晶种浓度为12g/L的优化条件下,雪硅钙石对实际废水中无机磷的回收率达89.08%。实验结果说明合成雪硅钙石对实际废水中的磷也有较好的回收效果。
冷冻法制取硝酸磷肥的酸解探索实验中,HNO_3浓度低并不影响酸解后溶出磷的量,且在室温下静置较短时间就可以溶出较多的磷。探索实验结果表明室温下用55%的HNO_3静置2h可溶出98.28%的磷;室温下用40.6%的HNO_3静置1h也可溶出95.23%的磷。说明以雪硅钙石回收磷容易被再利用。通过进一步实验研究,得到酸解阶段的优化条件为HNO_3浓度为55%,用量为理论值的290%,酸解时间为2h;而冷冻结晶阶段的优化条件为冷冻结晶时间在6～8h,冷冻温度为-5℃。
Phosphorus is not only an indispensable nutrient element for all the living forms, a nonrenewable and irreplaceable resource, but also an important factor which causes eutrophication of water bodies. Synthetic tobermorite contains neither heavy metals nor phosphorus and can giving out OH~- and Ca~(2+) itself, and also it can promote the crystallization of phosphate. So, Synthetic tobermorite is an ideal seed for the phosphorus recovery from wastewater. Meanwhile, phosphorus fertilizer can increase the production of the crop. 84%-90% of the phosphorite in the world is used for producing every kind of phosphorus fertilizer, so phosphorite is the main material for producing phosphorus fertilizer in industry. We are short of phosphorus and it can not renewable. Moreover, Ca_(10)(PO_4)_6F_2 is the main component in phosphorite and it is hard to dissolve in water, and also it will cause the pollution of fluorine. Thus, in order to reduce the amount of the exploitation of phosphorus and prolong the time we could use phosphorus, now what we should do is not only to recover phosphorus from wastewater, but also we should find a good way to recycle it.
The reaction of recovering phosphorus from wastewater by synthetic tobermorite can reach the equilibrium at about 24h. Thermodynamic study shows that△G﹤0, the value of△S is positive and△H﹥0 during the process of phosphorus recovery. These parameters demonstrate that the process of crystallization is endothermic and the phosphorus adsorption and crystallization by synthetic tobermorite as seed are favorable. Kinetics study shows that the rate constant increases with the increase of temperature, the reaction order decreases with the increase of temperature.
Our research group have got the optimized conditions of phosphorus recovery by synthetic tobermorite, those are pH=8, Ca/P=2 (molar ratio), seed contents 2～2.4g/L, surge speed 140r/min. Based on those optimized conditions, this research increases the amount of the seed and the wastewater. After repeat the recovery experiment for 55 times, the rate of dephosphorization is 82% and the production contains 35.02% phosphorus. This production is already can be the raw material for the phosphorus nitrate production as the high quality phosphorite. XRD、FTIR、SEM and EDS have been employed in testing recovery seed, the results showed that the main recovered product was hydroxyapatite with lower crystallization degree. The results of recovering phosphorus from the wastewater from hoggery show that when pH=8, Ca/P=2 (molar ratio), seed contents 12g/L, the rate of dephosphorization can reach 89.08%. So, synthetic tobermorite has a good quality for the phosphorus recovery from real wastewater.
The experiment of producing phosphorus nitrate by refrigeration shows that low concentration of HNO_3 will not infect the amount of phosphorus which is dissolved by HNO_3. And HNO_3 can dissolve most of the phosphorus within a short time under the room temperature. The result shows that under the room temperature, 55% HNO_3 can dissolve 98.28% phosphorus by reacting for 2 hours; 40.6% HNO_3 can dissolve 95.23% phosphorus by reacting for 1hour. All the results demonstrate that the phosphorus which is recovered by synthetic tobermorite can be easily recycled. After more research, the optimized conditions for dissolving by HNO_3 are the concentration of HNO_3 is 55%, the dosage of HNO_3 is 290% compare to the theoretic dosage, and the time for reaction is 2 hours. And the optimized conditions for the refrigeration process are the time for freezing is 6 to 8 hours, and the temperature should be -5℃.
引文
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[2]郝晓地,刘壮,刘国军.欧洲水环境控磷策略与污水除磷技术(上).给水排水, 1998, 24(8): 69-73
[3]唐云梯.实用环境保护数据大全.武汉:湖北人民出版社, 1993, 50–55
[4]杨桢奎.水域的富营养化及其防治对策.北京:中国环境科学出版社, 1989, 71-73
[5]刘延华,冯生华.对活性污泥过量摄磷发生条件的新认识.给水排水, 1997, (10):18-20
[6]邵林广.控磷除磷在水体富营养化控制中的作用.环境与开发, 1999, 14(2): 39-42
[7]杨丽华,卓奋.湖泊水体磷污染及其防治对策.污染防治技术, 1996, 9(2): 47-49
[8]愈栋,谢有奎,方振东等.污水除磷技术的现状与发展.重庆工业高等专科学校学报, 2004, 19(1): 9-12
[9]张杰,臧景红,杨宏等. A2/O工艺的固有缺欠和对策研究.给水排水, 2003, 3(29): 23-26
[10]华光辉,张波.城市污水生物除磷脱氮工艺中的矛盾关系及对策.给水排水, 2000, 12(26): 1-4
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[12]周雹,周丹. A2/O除磷脱氮工艺设计计算(上).给水排水, 2003, 3(29): 26-29
[13]顾小红,黄种买,虞启义.污水除磷技术的现状及发展趋势.再生资源研究, 2002, 3: 33-35
[14]段瑞文.化学辅助除磷在改良A2O工艺中的应用.中国给水排水, 2005, 21(8): 94-96
[15]郑兴灿.城市污水生物除磷脱氮工艺方案的选择.给水排水, 2003, 5(26): 1-4
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[17]张继华.化学沉淀法处理磷化废水.工业水处理, 2000, 20(5): 43-44
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[19]俞栋,谢有奎,方振东等.污水除磷技术的现状与发展.重庆工业高等专科学校学报, 2004, 19(1): 9-12
[20]许景文.水域的水质保护与氮磷去除技术的研究.污染防治技术, 1995, 8(3): 150-156
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[22] K.Kumashiro, H.Ishiwater, and Y.Nawamura. A pilot plant study on using seawateras a magnesium source for struvite precipitation. Paper of the 2nd International Conference on Phosphate Recovery for Recycling from sewage and animal wastes. Noordwijkerhout, the Netherlands,2001
[23] P.Battistoni, G.Fava, P.Pavan, et al. Phosphate removal in anaerobic liquors by struvite crystallization without addition of chemicals: Preliminary results. Water Research, 1997, 31(11): 2925-2929
[24] I.StrartfuL, M.D.Scrimshaw, J.N.Lester. Conditions influence the precipitation of magnesium ammonium phosphate. Water Research, 2001, 35(17): 4191-4199
[25] K.Suzuki, Y.Tanaka, K.Kuroda, et al. Recovery of phosphorous from swine wastewater through crystallization. Bioresource Technology, 2005, 96: 1544-1550
[26] Y.H.Song, P.G.Weidler, U.Berg. Calcite-seeded crystallization of calcium phosphate for phosphorus recovery. Chemosphere, 2006, 63: 236-243
[27] N.Karapinar, E.Hoffmann, H.H.Hahn. P-recovery by secondary nucleation and growth of calcium phosphates on magnetite mineral. Water Research, 2006, 40(6): 1210-1216
[28] N.Bellier, F.Chazarenc, Y.Comeau. Phosphorus removal from wastewater by mineral apatite. Water Research, 2006, 40: 2965-2971
[29]潘兆鲁.结晶学及矿物学.北京:地质出版社, 1984,7-16
[30]郭杰.诱导结晶法处理含磷废水.硕士论文.湖南,湖南大学,2006
[31]张盼,马鸿文.利用钾长石粉体合成雪硅钙石的实验研究.岩石矿物学杂志, 2005, 24(4): 333-338
[32]张蓓蓓,郑红,马鸿文等.以合成雪硅钙石为晶种回收废水中的磷.岩石矿物学杂志, 2007, 26(6): 553-557
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[40]张蓓蓓.合成雪硅钙石用于含磷废水中磷回收的实验研究.硕士论文.北京.中国地质大学(北京),2007:23
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[44]张跃庭.氟对硝酸磷肥生产的影响.磷肥与复肥, 2002, 17(3): 36-37
[45]魏华.硝酸磷肥酸解结晶过程的相图应用.磷肥与复肥, 1994, 3: 36-40
[46]张盼,马鸿文.利用钾长石粉体合成雪硅钙石的实验研究.岩石矿物学杂志, 2005, 24(4): 333-338
[2]郝晓地,刘壮,刘国军.欧洲水环境控磷策略与污水除磷技术(上).给水排水, 1998, 24(8): 69-73
[3]唐云梯.实用环境保护数据大全.武汉:湖北人民出版社, 1993, 50–55
[4]杨桢奎.水域的富营养化及其防治对策.北京:中国环境科学出版社, 1989, 71-73
[5]刘延华,冯生华.对活性污泥过量摄磷发生条件的新认识.给水排水, 1997, (10):18-20
[6]邵林广.控磷除磷在水体富营养化控制中的作用.环境与开发, 1999, 14(2): 39-42
[7]杨丽华,卓奋.湖泊水体磷污染及其防治对策.污染防治技术, 1996, 9(2): 47-49
[8]愈栋,谢有奎,方振东等.污水除磷技术的现状与发展.重庆工业高等专科学校学报, 2004, 19(1): 9-12
[9]张杰,臧景红,杨宏等. A2/O工艺的固有缺欠和对策研究.给水排水, 2003, 3(29): 23-26
[10]华光辉,张波.城市污水生物除磷脱氮工艺中的矛盾关系及对策.给水排水, 2000, 12(26): 1-4
[11]邱维,张智.城市污水化学除磷的探讨.重庆环境科学, 2002, 24(2): 81-84
[12]周雹,周丹. A2/O除磷脱氮工艺设计计算(上).给水排水, 2003, 3(29): 26-29
[13]顾小红,黄种买,虞启义.污水除磷技术的现状及发展趋势.再生资源研究, 2002, 3: 33-35
[14]段瑞文.化学辅助除磷在改良A2O工艺中的应用.中国给水排水, 2005, 21(8): 94-96
[15]郑兴灿.城市污水生物除磷脱氮工艺方案的选择.给水排水, 2003, 5(26): 1-4
[16]陈华.化学沉淀法除磷和生物法除磷的比较.上海环境科学, 1997, 16(8): 33-35
[17]张继华.化学沉淀法处理磷化废水.工业水处理, 2000, 20(5): 43-44
[18] Morse G K,Brett S W,Guy J A.,et al. Review: Phosphorus removal and recovery technologies. The Science of the Total Environment, 1998, 212: 69-81
[19]俞栋,谢有奎,方振东等.污水除磷技术的现状与发展.重庆工业高等专科学校学报, 2004, 19(1): 9-12
[20]许景文.水域的水质保护与氮磷去除技术的研究.污染防治技术, 1995, 8(3): 150-156
[21]陈利德,王偲.浅议污水厂的磷回收.环境工程, 2004, 8(24): 26-27
[22] K.Kumashiro, H.Ishiwater, and Y.Nawamura. A pilot plant study on using seawateras a magnesium source for struvite precipitation. Paper of the 2nd International Conference on Phosphate Recovery for Recycling from sewage and animal wastes. Noordwijkerhout, the Netherlands,2001
[23] P.Battistoni, G.Fava, P.Pavan, et al. Phosphate removal in anaerobic liquors by struvite crystallization without addition of chemicals: Preliminary results. Water Research, 1997, 31(11): 2925-2929
[24] I.StrartfuL, M.D.Scrimshaw, J.N.Lester. Conditions influence the precipitation of magnesium ammonium phosphate. Water Research, 2001, 35(17): 4191-4199
[25] K.Suzuki, Y.Tanaka, K.Kuroda, et al. Recovery of phosphorous from swine wastewater through crystallization. Bioresource Technology, 2005, 96: 1544-1550
[26] Y.H.Song, P.G.Weidler, U.Berg. Calcite-seeded crystallization of calcium phosphate for phosphorus recovery. Chemosphere, 2006, 63: 236-243
[27] N.Karapinar, E.Hoffmann, H.H.Hahn. P-recovery by secondary nucleation and growth of calcium phosphates on magnetite mineral. Water Research, 2006, 40(6): 1210-1216
[28] N.Bellier, F.Chazarenc, Y.Comeau. Phosphorus removal from wastewater by mineral apatite. Water Research, 2006, 40: 2965-2971
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