改性生物质材料制备及对水中砷吸附性能与处理工艺研究
发布时间：2018-08-30 12:55
【摘要】：为应对突发水环境砷污染事件,研发大流量、低流阻、低成本的应急吸附材料已成为一种实际的需求。本文以废弃生物质材料木屑和咖啡渣为基体,采用化学方法制备改性木屑吸附材料和改性咖啡纤维素吸附材料;考查其对水中砷的吸附性能,并开展相关吸附机理的探讨;采用改性木屑为吸附材料,分别建立吸附固定床工艺和吸附-超滤组合工艺,为水中砷的去除提供技术支持。以木屑为基体,环氧氯丙烷为醚化剂,二乙烯三胺为交联剂,采用醚化交联和铁氧化物沉积的方法制备改性木屑吸附材料。优化后的制备条件为:木屑与环氧氯丙烷的用量比例为1:3(即每千克木屑需要3 L环氧氯丙烷),木屑与二乙烯三胺的用量为1:1(即每千克木屑需要1 L二乙烯三胺),醚化反应温度为90℃,醚化反应60 min,交联反应温度为70℃,交联反应时间为120 min。实验结果表明,醚化反应温度和醚化剂用量是吸附材料制备过程中的关键影响因素。改性木屑吸附材料适用的最佳pH值范围为5-6,对As(III)和As(V)的最大吸附容量分别为13.2和46.1 mg/g,优于文献中报道的结果。以咖啡渣为基体,经过氢氧化钠溶液预处理后,用5%次氯酸钠溶液反复漂洗提取咖啡纤维素,以聚乙烯亚胺(PEI)为氨化剂,以戊二醛为交联剂,经络合Fe(III)后制备改性咖啡纤维素吸附材料。优化后的制备条件为:PEI的浓度为5%,氨基反应时间为120 min,交联剂戊二醛的浓度为0.1%,交联反应时间为240 min,Fe(NO3)3溶液的浓度为500 mg/L。与改性木屑吸附材料不同的是,改性咖啡纤维素络合Fe(III)后,没有采用加碱陈化的方法负载铁氧化物,这是由于络合Fe(III)可以显著增加咖啡纤维素表面的Zeta电位,从而更好的实现对As(V)阴离子的吸附。弱酸性条件有利于As(V)的吸附,改性咖啡纤维素对As(V)的最大吸附容量为91 mg/g。改性咖啡纤维素吸附As(V)后,还可以实现对水中Cu(Ⅱ)的连续吸附,对Cu(Ⅱ)的最大吸附容量达到200 mg/L。分别对上述两种改性生物质材料的吸附过程进行相关的模型拟合,结合两种改性生物质材料的特点探讨其对水中砷的吸附机理。吸附反应动力学研究结果表明,两种改性生物质材料对水中砷的吸附过程均较好地符合拟二级反应动力学方程,表明两种改性生物质材料对砷的吸附是一个以化学吸附为主的过程。Langmuir模型对两种改性生物质材料吸附砷的拟合效果较好,表明砷在两种改性生物质材料表面的吸附是单分子层化学吸附。吸附传质机理模型表明,内部传质系数[kLa]d在总传质系数[kLa]g中的比例较大,表明主要的传质阻力来自于砷与改性木屑表面活性吸附位点之间的物理化学反应,以及砷向吸附材料孔隙内部的扩散;对于改性咖啡纤维素,主要的传质阻力来自于As(V)与改性咖啡纤维素表面活性吸附位点之间的物理化学反应。结合两种改性生物质材料的特点探讨其对水中砷的吸附机理,结果表明,负载在木屑表面的铁氧化物对As(III)的吸附起主要作用,而接枝氨基对As(V)的吸附起主要作用;对于改性咖啡纤维素,接枝氨基和络合三价铁离子均显著增加了吸附材料表面的Zeta电位,从而大大提高了对As(V)阴离子的吸附效果,As(V)和Cu(Ⅱ)在改性咖啡纤维素表面的连续吸附是静电引力和表面络合反应共同作用的结果。为了模拟实际应急处置中吸附坝的动态吸附过程,设计固定床吸附工艺装置。对比不同填充高度及进水流量下的吸附穿透曲线。采用动态吸附模型对吸附过程进行拟合分析,Thomas模型拟合结果表明,当总砷的初始浓度为10 mg/L,流量为4.8 mL/min时,改性木屑滤床的饱和吸附容量达到15.6 mg/g;BDST模型拟合结果表明,改性木屑最大动态吸附速率常数达到3.13×10-4 L/min·mg,固定床穿透时间的模型拟合值和实测值之间的差异很小,表明BDST模型可以较好的预测不同柱高条件下,滤床到达饱和的穿透时间。为模拟实际应急处置中移动式处置过程,设计吸附-超滤组合工艺,完成对水中砷污染物的有效去除,同时实现对吸附饱和后吸附材料的有效分离。实验结果表明,曝气搅拌不仅可以使吸附材料在反应器中的混合更加均匀,还会增加水中溶解氧的含量,加速As(III)向As(V)的氧化,从而提高总砷的去除效率。对模拟含砷地表水条件下总砷的去除效果进行了研究,当总砷的初始浓度为0.1 mg/L时,经该组合工艺处理后出水砷浓度优于I类地表水环境质量标准。研究表明,本文研制的生物质吸附材料及吸附处理工艺适用于突发水环境砷污染事件的应急处置技术要求。
[Abstract]:In order to cope with the arsenic pollution incidents in the water environment, it has become a practical demand to develop high flow rate, low flow resistance and low cost emergency adsorption materials. Adsorption properties and adsorption mechanism were discussed. Modified wood chips were used as adsorption materials to establish adsorption fixed bed process and adsorption-ultrafiltration combined process, respectively, to provide technical support for the removal of arsenic in water. The optimized preparation conditions were as follows: the ratio of sawdust to epichlorohydrin was 1:3 (that is, 3 L epichlorohydrin per kg of sawdust), the ratio of sawdust to diethylenetriamine was 1:1 (that is, 1 L diethylenetriamine per kg of sawdust), the etherification temperature was 90 C, the etherification reaction was 60 min, and the cross-linking reaction was trans-linked. The results showed that the etherification reaction temperature and the dosage of etherifying agent were the key factors in the preparation of the adsorbent. The optimum pH range of the modified wood chip adsorbent was 5-6, and the maximum adsorption capacity of As (III) and As (V) was 13.2 and 46.1 mg/g, respectively, which were better than those reported in literature. Result: The modified coffee cellulose adsorbent material was prepared by using coffee residue as matrix, pretreated with sodium hydroxide solution, rinsed and extracted repeatedly with 5% sodium hypochlorite solution, polyethylenimine (PEI) as ammoniating agent, glutaraldehyde as crosslinking agent, and complexed with Fe (III). The reaction time was 120 min, the concentration of glutaraldehyde was 0.1%, the crosslinking reaction time was 240 min, and the concentration of Fe (NO3) 3 solution was 500 mg/L. Unlike the modified sawdust adsorption material, the modified coffee cellulose complex with Fe (III) did not use alkali aging method to load iron oxide, because the complex Fe (III) could significantly increase the content of Caffee. The Zeta potential on the surface of enkephalin cellulose can better realize the adsorption of As (V). Weak acidity conditions are favorable for the adsorption of As (V). The maximum adsorption capacity of modified coffee cellulose for As (V) is 91 mg/g. After adsorbing As (V), the modified coffee cellulose can also achieve the continuous adsorption of Cu (II) in water, and the maximum adsorption capacity of Cu (II) can reach the maximum. To 200 mg/L, the adsorption processes of the two modified biomass materials were modeled and the adsorption mechanism of arsenic in water was discussed according to the characteristics of the two modified biomass materials. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was a chemical adsorption process. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was monolayer chemical adsorption. The larger proportion of internal mass transfer coefficient [kLa] D in total mass transfer coefficient [kLa] g indicates that the main mass transfer resistance comes from the physicochemical reaction between arsenic and the surface active adsorption sites of modified sawdust, as well as the diffusion of arsenic into the pores of adsorption materials; for modified coffee cellulose, the main mass transfer resistance comes from As (V) and modified coffee. The adsorption mechanism of arsenic in water was discussed based on the characteristics of two modified biomass materials. The results showed that the adsorption of As (III) by iron oxides loaded on wood chips played a major role, while the adsorption of As (V) by grafted amino groups played a major role. The Zeta potential on the surface of the adsorbent material was significantly increased by grafting amino group and complexing ferric ion, and the adsorption effect of As (V) and Cu (II) on the modified coffee cellulose surface was greatly improved. The continuous adsorption of As (V) and Cu (II) on the modified coffee cellulose surface was the result of the interaction of electrostatic attraction and surface complexation reaction. The adsorption process was fitted and analyzed by dynamic adsorption model. The results of Thomas model showed that when the initial concentration of total arsenic was 10 mg/L and the flow rate was 4.8 mL/min, the modified sawdust filter bed was saturated. The adsorption capacity reached 15.6 mg/g; BDST model fitting results showed that the maximum dynamic adsorption rate constant of modified sawdust reached 3.13 *10-4 L/min.mg, and the difference between model fitting value and measured value of fixed bed penetration time was very small, indicating that BDST model can better predict the filter bed penetration time to saturation under different column heights. A combined process of adsorption and ultrafiltration was designed to remove arsenic pollutants effectively and separate adsorbents saturated by adsorption. The experimental results show that aeration stirring can not only make the mixture of adsorbents more uniform in the reactor, but also increase the dissolution of adsorbents in water. The removal efficiency of total arsenic in simulated arsenic-containing surface water was studied. When the initial concentration of total arsenic was 0.1 mg/L, the concentration of arsenic in effluent treated by the combined process was better than that of the environmental quality standard of class I surface water. Material adsorption materials and adsorption process are suitable for emergency treatment of arsenic contamination in water environment.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X52
[Abstract]:In order to cope with the arsenic pollution incidents in the water environment, it has become a practical demand to develop high flow rate, low flow resistance and low cost emergency adsorption materials. Adsorption properties and adsorption mechanism were discussed. Modified wood chips were used as adsorption materials to establish adsorption fixed bed process and adsorption-ultrafiltration combined process, respectively, to provide technical support for the removal of arsenic in water. The optimized preparation conditions were as follows: the ratio of sawdust to epichlorohydrin was 1:3 (that is, 3 L epichlorohydrin per kg of sawdust), the ratio of sawdust to diethylenetriamine was 1:1 (that is, 1 L diethylenetriamine per kg of sawdust), the etherification temperature was 90 C, the etherification reaction was 60 min, and the cross-linking reaction was trans-linked. The results showed that the etherification reaction temperature and the dosage of etherifying agent were the key factors in the preparation of the adsorbent. The optimum pH range of the modified wood chip adsorbent was 5-6, and the maximum adsorption capacity of As (III) and As (V) was 13.2 and 46.1 mg/g, respectively, which were better than those reported in literature. Result: The modified coffee cellulose adsorbent material was prepared by using coffee residue as matrix, pretreated with sodium hydroxide solution, rinsed and extracted repeatedly with 5% sodium hypochlorite solution, polyethylenimine (PEI) as ammoniating agent, glutaraldehyde as crosslinking agent, and complexed with Fe (III). The reaction time was 120 min, the concentration of glutaraldehyde was 0.1%, the crosslinking reaction time was 240 min, and the concentration of Fe (NO3) 3 solution was 500 mg/L. Unlike the modified sawdust adsorption material, the modified coffee cellulose complex with Fe (III) did not use alkali aging method to load iron oxide, because the complex Fe (III) could significantly increase the content of Caffee. The Zeta potential on the surface of enkephalin cellulose can better realize the adsorption of As (V). Weak acidity conditions are favorable for the adsorption of As (V). The maximum adsorption capacity of modified coffee cellulose for As (V) is 91 mg/g. After adsorbing As (V), the modified coffee cellulose can also achieve the continuous adsorption of Cu (II) in water, and the maximum adsorption capacity of Cu (II) can reach the maximum. To 200 mg/L, the adsorption processes of the two modified biomass materials were modeled and the adsorption mechanism of arsenic in water was discussed according to the characteristics of the two modified biomass materials. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was a chemical adsorption process. The Langmuir model showed that the adsorption of arsenic on the surface of the two modified biomass materials was monolayer chemical adsorption. The larger proportion of internal mass transfer coefficient [kLa] D in total mass transfer coefficient [kLa] g indicates that the main mass transfer resistance comes from the physicochemical reaction between arsenic and the surface active adsorption sites of modified sawdust, as well as the diffusion of arsenic into the pores of adsorption materials; for modified coffee cellulose, the main mass transfer resistance comes from As (V) and modified coffee. The adsorption mechanism of arsenic in water was discussed based on the characteristics of two modified biomass materials. The results showed that the adsorption of As (III) by iron oxides loaded on wood chips played a major role, while the adsorption of As (V) by grafted amino groups played a major role. The Zeta potential on the surface of the adsorbent material was significantly increased by grafting amino group and complexing ferric ion, and the adsorption effect of As (V) and Cu (II) on the modified coffee cellulose surface was greatly improved. The continuous adsorption of As (V) and Cu (II) on the modified coffee cellulose surface was the result of the interaction of electrostatic attraction and surface complexation reaction. The adsorption process was fitted and analyzed by dynamic adsorption model. The results of Thomas model showed that when the initial concentration of total arsenic was 10 mg/L and the flow rate was 4.8 mL/min, the modified sawdust filter bed was saturated. The adsorption capacity reached 15.6 mg/g; BDST model fitting results showed that the maximum dynamic adsorption rate constant of modified sawdust reached 3.13 *10-4 L/min.mg, and the difference between model fitting value and measured value of fixed bed penetration time was very small, indicating that BDST model can better predict the filter bed penetration time to saturation under different column heights. A combined process of adsorption and ultrafiltration was designed to remove arsenic pollutants effectively and separate adsorbents saturated by adsorption. The experimental results show that aeration stirring can not only make the mixture of adsorbents more uniform in the reactor, but also increase the dissolution of adsorbents in water. The removal efficiency of total arsenic in simulated arsenic-containing surface water was studied. When the initial concentration of total arsenic was 0.1 mg/L, the concentration of arsenic in effluent treated by the combined process was better than that of the environmental quality standard of class I surface water. Material adsorption materials and adsorption process are suitable for emergency treatment of arsenic contamination in water environment.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X52
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