辐射接枝制备功能吸附材料及对金离子的吸附性能研究

Millions of tons of spent electrical and electronic devices are discarded every year. In a rough estimate, the percentage composition of different metals by weight in a mobile phone, for example, is: copper, 15%; iron, 3%; zinc, 1%; and less than 1% of a number of metals such as tin, palladium and gold. Although the portion of gold is very low compared to the other metals in one piece of a device, the amount of gold disposed in this form is much higher than the content in gold ore itself. Discarding of such electronic waste indicates not only the loss of huge amounts of resources but also the threat of environmental pollution. With technological advances, many methods of rare metal, especially gold recovery have been formulated. The most common processes at present are chloride leaching and cyanide leaching. From an economic point of view, the recovery process should be such that the precious metals are highly selectively separated from base metals such as iron, copper, and zinc that often coexist with the precious metals in disproportionate amounts. Attempts have been made in recent years to develop new processes consisting of total leaching in hydrochloric acid containing chlorine gas or hypochlorite, followed by solvent extraction and ion exchange. In the new processes, adsorbents with high selectivities and high loading capacities are strongly required to simplify the process and decrease the costs. Radiation technique is considered as a competitive method to prepared polymer adsorbent by the benefits of economical, clean and efficient. Radiation-induced graft polymerization has been a mature technique for decades to modify variety of matrix and further develop into environmental application. In this project, we will develop a new adsorbent utilizing radiation graft polymerization for gold recovery. Polyethylene-coated polypropylene or polyethylene terephthalate (PE/PP or PE/PET) non-woven fabric will be used as a trunk material for polymerization. The tertiary amine group modified fiber will be prepared by radiation-induced graft polymerization of DMAEMA and DEAEMA, respectively. Recovery of Au(III) will be carefully investigated with batch and column model. Sorption isotherm, sorption kinetics, sorption capacity of Au(III) and effect of hydrochloric acid (HCl)and Cu2+ in solution will be investigated in order to elucidate the mechanism of adsorption. Not only pure Au(III) solution but also simulated leaching solution will be used to study the sorption behavior. The behaviors of desorption of Au(III) will be carefully optimized. The performance of adsorption against Au(III) and the service life of the adsorbent will be evaluated in an attempt to achieve high adsorption capacity and service life of 6 cycles.

从电子垃圾中回收贵金属具有显著的经济价值和环保意义。在现有的贵金属回收方法中，吸附法是一种最具前途的固-液分离方法，其关键在于制备低价而高效的吸附材料。同时，对于从电子垃圾中回收金则要考察高酸度、高浓度共存离子条件下选择性吸附目标离子的材料和方法。本项目拟利用预辐射接枝技术，研究一种新型金离子（Au(III)）的叔胺基吸附材料。选择高强度且耐酸碱的聚乙烯(PE)包覆聚丙烯（PP）、PE包覆聚对苯二甲酸乙二酯（PET）为基材，接枝2-(二甲氨基)甲基丙烯酸乙酯（DMAEMA）和2-(二乙氨基)甲基丙烯酸乙酯（DEAEMA），获得叔胺基类吸附材料；研究该吸附材料对Au（III）的吸附行为，阐明吸附机理；研究脱附方法；并利用模拟贵液在实验室评估材料对Au（III）的吸附性能和使用寿命。通过优化实验条件，获得在高酸度、高浓度共存离子条件下具有高吸附容量和吸附效率且能重复使用6次以上的吸附材料。

通过预辐射溶液接枝的方法将DMAEMA单体接枝到PE/PP和PE/PET纤维上。通过红外光谱上出现的叔氨基的伸缩振动峰，可以证明成功地将PDMAEMA链段接枝到PE/PP纤维上；通过对接枝反应时间，辐照吸收剂量，接枝溶剂组分和接枝反应温度与接枝率之间关系的研究，发现了50 kGy，60℃和5 h可以获得接枝率超过120%的吸附材料，确定该条件作为接枝反应的最优条件；利用SEM对纤维表面形貌进行表征，发现接枝DMAEMA使得PE/PP纤维的直径明显增加，纤维没有出现明显的破裂和损伤。拉力测试表面，辐射对PE/PP纤维机械性能影响较大，而DMAEMA的接枝对PE/PP纤维的机械性能没有显著影响。相对于PE/PP,由于PET的惰性，接枝所需吸收剂量要高于200 kGy,才能获得接枝率高于100%，可以应用于吸附领域的材料。因此需要选择PE/PP为基材合成叔氨基的吸附材料。. 研究了Dg= 51.6%的PE/PP-g-PDMAEMA纤维在纯的Au（III）溶液的吸附动力学、热力学规律。结果显示PE/PP-g-PDMAEMA纤维对Au（III）的吸附过程能够很好的符合两种动力学模拟：准一级动力学方程和准二级动力学方程模拟。吸附热力学符合Freundlich等温吸附模型。材料在高浓度的Au溶液中吸附效率也非常高。在0.1, 0.5 和1.0 g L-1Au溶液中吸附率达到97%, 吸附率在1.5 g L-1 溶液中降低到88.3%，在2.5 g L-1 降低到75.9%。但材料的吸附量是随初始浓度的增加而增加，材料最高的吸附容量可达到 949.3 mg g-1 (4.8 mmol g-1)。吸附上的Au的摩尔浓度远高与材料上功能团的浓度。材料对Au的吸附并不是简单的物理或化学吸附，吸附上的Au（III）被原位还原成Au单质，材料的颜色变深紫色。当纳米金逐渐生长，金黄色的金薄片产生。吸附之后的Au可以用 0.2 mol L-1硫脲与0.01 mol L-1HCl洗脱。洗脱液总体积在100 BV。经过5次吸附脱附循环之后材料的吸附效率仅降低了6.5%。该材料具有很好的选择吸附性，在模拟贵液中仍然对Au有很好的选择吸附性能，Au(III)的Kd比共存离子高出 104–105 倍。结果显示该纤维吸附材料对Au有非常好的吸附应用前景。