Knowledge Management System Of Institute of process engineering,CAS
水资源短缺与水污染共存的局面，严重威胁着人们的生活和经济的可持续发展。目前，选矿业作为用水大户，废水排放量约2亿吨/年，占全国工业废水的10%。选矿废水中通常残留大量微细尾矿颗粒、重金属离子以及选矿药剂等，直接排放将造成对环境的污染和水资源的极大浪费。而若直接回用于选矿流程，微细颗粒及重金属离子是造成浮选指标恶化的两大关键因素，将严重降低选矿行业的经济效益。因此对选矿废水进行高效处理，实现选矿废水的优级循环利用，并确保选矿工序指标正常和生产稳定，具有巨大的经济、环境和社会效益。本课题的研究思路是针对选矿废水中微细颗粒和重金属离子的快速高效去除，设计合成了以无机纳米颗粒为核，高分子链为支链的“星型”结构无机-有机杂化材料，以实现无机与有机组分的均匀杂化及高效协同作用。本研究的主要内容及结果如下：（1）针对颗粒脉石成分比重小、粒度细、表面带负电的特点，合成了以纳米氢氧化铝为核，聚丙烯酰胺为支链的无机-有机杂化絮凝剂氢氧化铝-聚丙烯酰胺（Al-PAM），并将该絮凝剂用于颗粒平均粒径为30 μm，ζ电位为-5.26 mV的氰化尾矿悬浮液的絮凝处理。实验结果表明，Al-PAM可将尾矿悬浮液中颗粒的初始沉降速率提高18.5倍，上清液除浊率可达98.5%，并在0.5 mg/L的用量下达到瓜尔胶（GG）用量为4 mg/L时的最佳絮凝效果。另外，针对于不同颗粒粒度的尾矿悬浮液的絮凝处理，与聚丙烯酰胺（PAM）相比，颗粒粒度越细，杂化型絮凝剂Al-PAM的絮凝优势越明显，说明正电氢氧化铝的引入在负电微细尾矿颗粒的絮凝中起到关键作用，电中和机理和吸附架桥机理高效协同作用实现了Al-PAM对负电微细尾矿颗粒的高效絮凝。（2）基于“星型”杂化絮凝剂Al-PAM对微细颗粒的絮凝优势，通过丙烯酰胺（AM）和阳离子单体二甲基二烯丙基氯化铵（DMDAAC）的共聚合反应，研制出杂化共聚型絮凝剂氢氧化铝-聚（丙烯酰胺-二甲基二烯丙基氯化铵）（Al-P(AM-DMDAAC)），以便合理调整材料的正电荷负载量，提高其对高负电微细颗粒的絮凝性能。将该絮凝剂用于高硅体系悬浮液（硅微粉悬浮液：颗粒平均粒径为5 μm，ζ电位为-27.46 mV）的处理，对比絮凝剂Al-PAM和Al-P(AM-DMDAAC)的絮凝性能。实验结果表明，Al-P(AM-DMDAAC)可将硅微粉悬浮液的上清液浊度由50000 NTU降低至9.066 NTU，而在同等投加量下，相对分子量相近的Al-PAM仅将上清液浊度降低至2032 NTU。与Al-PAM相比，Al-P(AM-DMDAAC)的电中和能力明显提升（ζ电位提高了3~6倍），因此电中和能力大小是决定絮凝剂对高负电微细颗粒悬浮液除浊性能优劣的关键因素。（3）为了实现选矿废水中重金属离子的高效去除，在Al-PAM杂化絮凝结构的基础之上，将二硫代氨基甲酸盐基团（DTC）引入聚丙烯酰胺支链中，成功研制出一种新型吸附剂氢氧化铝-聚丙烯酰胺-二甲基二烯丙基氯化铵（Al-PAM-DTC）。将该吸附剂用于重金属离子的吸附，其对Cu2+的饱和吸附量可达429.067 mg/g，Pb2+的饱和吸附量可达892.505 mg/g。Al-PAM-DTC在含正电铝矾土颗粒和重金属离子二元体系废水的处理中，对重金属离子及浊度去除率均达到97%以上，而对负电硅微粉颗粒的浊度去除率仅达85%。Al-PAM-DTC对Cu2+和Pb2+的吸附属于自发的吸热过程，并且该吸附属于化学吸附，取决于含氮、含氧和黄原酸功能基团对重金属离子的配位螯合。（4）考虑到吸附剂Al-PAM-DTC无法实现对负电微细颗粒的高效絮凝，将DTC引入杂化共聚物Al-P(AM-DMDAAC)中，制备得到吸附剂氢氧化铝-聚（丙烯酰胺-二甲基二烯丙基氯化铵）-二硫代氨基甲酸盐（Al-P(AM-DMDAAC)-DTC），以便通过阳离子单体DMDAAC减弱DTC的负电效应。该吸附剂能更好地适用于负电硅微粉颗粒与重金属离子的共存体系，可实现高达95%以上的浊度去除率以及90%以上的重金属离子去除率。Al-P(AM-DMDAAC)-DTC对Cu2+ 和Pb2+的饱和吸附量分别可达317.777 mg/g 和 586.699 mg/g。（5）通过对杂化材料螯合重金属离子机理的探索性研究，发现含氮、含氧和黄原酸基团对有机染料具备一定的吸附潜力，故将其应用拓展至有机染料废水。实验结果表明，吸附剂Al-PAM-DTC用于50mg/L亚甲基蓝（MB）废水的处理，可在30 min内吸附脱除98%的MB。同目前报道吸附材料相比，Al-PAM-DTC对MB的饱和吸附量可高达1088.55 mg/g，并且该吸附过程放热且为化学吸附，归功于含氮、含氧和黄原酸基团与染料分子间的静电吸引和化学键合。;The water shortage and pollution seriously threaten the people's life and sustainable development of economy. Currently, as the major water users, the annual discharge of mineral processing wastewater is 200m tonnes. The mineral processing wastewater contains fine tailing particles, heavy metal ions and flotation reagents, its direct discharge would cause the environmental pollution as well as a great waste of water resources. However, if directly recycled, the fine particles and heavy metal ions would lead to the deterioration of flotation indexes and reduce the economic benefit of mineral processing industry. Therefore, the mineral processing wastewater efficiently treated could be recycled and ensure the normal and stable index of production, which has great economic, environmental and social significance. In this study, the hybrid materials, showing a “star-like” structure that an organic nano-particle acts as core linking polymer arm chains, have been prepared. In the hybrid material, the inorganic and organic components are well mixed and act synergistically to remove fine particles and heavy metal ions rapidly and efficiently in mineral processing wastewater. The efficient treatment of mineral processing wastewater could recycle the wastewater and ensure the normal and stable index of production. The main works and results are as follows:Cyanide tailing suspension was selected as the flocculation object, the main component of particles in which was gangue, and thus the specific density of particles was low. In addition, the particles were fine with an average size of 30 μm and negatively-charged with a ζ potential of -5.26 mV. So the particles settled slowly by gravity from cyanide tailing suspensios. In view of this, an hybrid material Al-PAM was synthesized with a “star-like” structure that Al(OH)3 colloids acts as cores linking polyacrylamide arm chains. The Al-PAM served as flocculant for the cyanide tailing suspensions, the flocctant GG was used for comparison. The floccation experiments indicated that Al-PAM increased the initial settling rate of particles by 18.5 times of blank without flocculants, and the turbidity removal efficiency of supernatant by Al-PAM was 98.5%. Meanwhile, Al-PAM achieved the equivalent effect at lower addition of 0.5 mg/L with GG at its optimum dosage of 4 mg/L. When used in the cyanide tailing suspensions with average particle size of 30 μm, 14 μm and 3 μm respectivle, Al-PAM all performed better than PAM. What’s more, the much fine the particles were, the more superior Al-PAM performed. Therefore, the Al(OH)3 colloids in Al-PAM played a significant role in flocculation of negatively-charged fine particles. The excellent performance of Al-PAM could be attributed to the charge neutralization of Al(OH)3 colloids and bridge adsorption of extended PAM chains.Considering the flocculation advantage of inorganic-organic polymer Al-PAM for fine particles, the cationic hybid copolymer Al-P(AM-DMDAAC) was obtained through the copolymerization of acylamide and dimethyldiallylammonium chloride onto the surface of Al(OH)3 colloidal paticles, in order to effectively flocculate the fine particles with high negative surface charge. The flocculation sample was silica suspensions, the partilces in which had an average size of 5 μm and high ζ potential of -27.46 mV. The Al-PAM was also investigated in silica suspensions for comparison. The results showed that Al-P(AM-DMDAAC) reduced the supernatant turbidity of silica suspensions to 9.066 NTU from 50000 NTU in blank experiment. However, Al-PAM which had a similar molecular weight with Al-P(AM-DMDAAC) just reduced the supernatant turbidity to 2032 NTU. The charge neutralizing ability of Al-P(AM-DMDAAC) was obviously improved compared with Al-PAM (ζ potential increased by 3~6 times), which indicated that charge neutralizing ability is a significant parameter in determining the performance of flocculants for the removal of fine particles with high negative surface charge. The adsorbent Al-PAM-DTC was successfully synthesized by grafting dithiocarbamate onto the “star-like” hybrid structure of Al-PAM for efficient removal of heavy metal ions in mineral processing wastewater. The maximum adsorption capacities of Al-PAM-DTC for Cu2+ and Pb2+ were 416.959 mg/g and 892.505 mg/g, respectively. Al-PAM-DTC was able to remove above 97% of positively-charged bauxite particles as well as 97% of Cu2+ or Pb2+ simultaneously through flocculation and chelation in the binary systems containing fine particles and heavy metal ions. However, the removal efficiency of negatively-charged partilcles by Al-PAM-DTC was only 85%. Chemisorption was the adsorption mechanism of Al-PAM-DTC for Cu2+ and Pb2+, which was attributed to the chelation of nitrogen-containing, oxygen-containing and xanthate functional groups with metal ions. In view of the weak flocculation of Al-PAM-DTC for negatively-charged particles, the DTC was grafted onto the hybrid copolymer Al-P(AM-DMDAAC) to obtain Al-P(AM-DMDAAC)-DTC in order to neutralize the negative charge of DTCs by cationic DMDAAC. Al-P(AM-DMDAAC)-DTC performs better in the coexisting system of negatively-charged silica particles and heavy metal ions , achieving more than 97% of turbidity removal and 90% of Cu2+ or Pb2+ removal. The saturated adsorption capacities of Al-P(AM-DMDAAC)-DTC for Cu2+ and Pb2+ were 317.777 mg/g and 586.699 mg/g, respectively.Al-PAM-DTC was further used for the adsorption of MB to investigate the adsorption potential of functional chelation groups for dyes. Al-PAM-DTC could quickly and efficiently remove more than 98% of MB from 50mg/L of the synthetic dye wastewater within 30 min. In addition, it demonstrated much higher MB adsorption capacity of 1088.55 mg/g than any other reported synthetic materials, and thus could be used for effective treatment of dyes wastewater. The MB adsorption was a spontaneous and exothermic process, and the chemisorption mechanism could be attributed to the electrostatic attraction and coordination of nitrogen-containing, oxygen-containing and xanthate functional groups with dyes.
|刘娅. 聚丙烯酰胺基无机-有机杂化材料的制备及性能研究[D]. 中国科学院研究生院,2018.|
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