废旧皮革中铬的浸取工艺研究

Chromium leaching from scrap leather

为了解决废弃的废旧皮革用品潜在的环境污染问题并使其资源化,采用正交实验的方法,通过分批实验研究了温度、时间、浓度对皮革中铬浸出率的影响,比较了草酸、甲酸、乙酸和H_2SO_4对铬的浸出效果,还比较了草酸、草酸钠、草酸铵水溶液的铬浸取效果以及不同浓度的草酸铵水溶液对低铬皮革和高铬皮革的浸取效果,在此基础上,考察了多级浸取及多级逆流浸取效果。实验结果表明,草酸浸取效果远比其它三种酸好,而与其两种盐相比,没有明显差别,草酸浓度越高对皮革破坏作用越强,而草酸铵浓度越高反而有利于抑制皮革水解。不同皮革性质差别很大,虽然通过多级浸取都可以脱掉97%以上的铬,但也会导致皮革明显水解。要实现皮革与铬完全分离而又不破坏皮革是很困难的。

To address potential environmental contamination of dumped scrap leather stuffs and make those be useful resources, orthogonal experimental methodology was adopted to design batch experiments to investigate the effect of temperature, time, concentration and different acids （oxalic acid, formic acid, acetic acid and sulfuric acid）, on chromium removal yield of the leather. Chromium leaching efficacy from leathers with low and high dosage chromium by oxalic acid, sodium oxalate and ammonium oxalate of different concentrations were also com- pared. Moreover, cross-flow and concurrent flow multistage leaching were evaluated. Experimental resuhs show that oxalic acid leaches much more chromium than the other three acids but has the same efficacy as sodium ox- alate and ammonium oxalate. Leather dissolution rises with the concentration of oxalic acid increasing. However, the tendency seems opposite for ammonium oxalate. Leathers showed substantial resistance difference to leaching. Although chromium leaching yield may reach up to 97% by multistage leaching, increasing temperature, lengthen- ing contact time or concentration rising, it will result more leather dissolution. It is difficult to extract all chromium from leather and keep the matrix intact at the same time.