在制革行业中，含铬废水主要来源于鞣制部分，对于该部分废水，常 采用化学沉淀法来回收利用废水中的铬。加碱沉淀后，能够去除废水中 98% 的铬，但剩余废水中仍含有少量的铬，使得出水很难达标。因此，对于加 碱沉淀后的低浓度含铬废水，需要进一步处理，才能达到国家排放标准 (Cr(VI)<0.1mg/L，总铬<1.5mg/L)。 对于低浓度含铬废水，常用的处理方法有离子交换法、膜分离法、吸 附法等，但这类方法因成本较高，较难在我国大多数企业中推广并应用。 近年来，许多学者用各种廉价的材料来作为吸附剂处理废水中的重金属离 子，并取得了一定的效果。锆、铝鞣制或多金属结合鞣制是近年来替代铬 鞣、赋予成品革的特有属性的一类鞣制工艺，目前已经逐渐在企业中得到 应用。该部分废水在经过沉淀处理过程后产生的废弃物主要成分为各种金 属的氢氧化物。 本课题以非铬鞣废水中的废弃物为目标，针对加碱沉淀处理后的低浓 度铬鞣废水，利用非铬鞣废水沉淀物将其进行改性或直接作为吸附剂处理 低浓度含铬废水，研究其对 Cr 3+ 的吸附性能。制备的吸附材料主要为 Zr(OH) 4 、Al(OH) 3 、ZrO 2 、Al 2 O 3 -TiO 2 以及实际鞣制废水沉淀物，分别用上 述几种材料作为吸附剂，以 Cr 3+ 作为目标污染物，通过对吸附剂的表征和 吸附实验结果，研究上述材料对 Cr 3+ 的吸附特性，得出如下结果。 （1）Zr(OH) 4 和 ZrO 2 对 Cr 3+ 的吸附 制备的材料 Zr(OH) 4 的 XRD 分析表明，500℃烧结 3h 后可以完全转变 成 ZrO 2 。 Zr(OH) 4 和 ZrO 2 对 Cr 3+ 的吸附量随着温度的升高而增大，吸附过程均 符合 Freundlich 等温吸附模型；25℃，在实验条件下，Zr(OH) 4 和 ZrO 2 对 Cr 3+ 的吸附量分别可达 81.30 mg/g 和 126.7 mg/g，在吸附 60 min 左右基本 达到吸附平衡，吸附动力学可以利用二级动力学方程进行拟合；Na + 、Ca 2+ 在吸附过程中与 Cr 3+ 产生竞争作用而降低 Cr 3+ 的吸附效率；在 pH<4.0 时， Cr 3+ 的去除主要为吸附作用，当 pH>4.0 时，Cr 3+ 的去除为沉淀和吸附的混 合过程。材料吸附 Cr 3+ 前后的 SEM-EDS 分析表明，吸附剂表面的 OH - 等阴II 离子基团在吸附过程中发挥主要作用。 （2）Al(OH) 3 对溶液中 Cr 3+ 的吸附 25℃，在实验 Cr 3+ 浓度范围内，Cr 3+ 的最大吸附量为 49.29 mg/g，并且 吸附量随着溶液浓度的升高而增大，吸附属于多层吸附，吸附动力学可用二 级动力学方程拟合。吸附过程容易受到 pH 的影响，在 pH=7-8 时，Cr 3+ 的去 除率较高；盐离子 Na + 、Ca 2+ 对 Cr 3+ 的吸附过程存在不同程度的竞争抑制作 用，且 Ca 2+ 的抑制作用要强于 Na + ；去除实际铬鞣废液中的 Cr 3+ 时，在使用 相同吸附剂用量处理相同浓度的 Cr 3+ 溶液时，Cr 3+ 的去除率偏低，其原因是 实际铬鞣废水的成分复杂，其中的杂质成分会与 Cr 3+ 产生竞争吸附。 （3）Al 2 O 3 -TiO 2 对溶液中 Cr 3+ 的吸附 合成的三种 Al 2 O 3 -TiO 2 、Al 2 O 3 -ZrO 2 、ZrO 2 -TiO 2 吸附剂中，Al 2 O 3 -TiO 2 对 Cr 3+ 的吸附效率较高，且在 pH=6-10 时，Al 2 O 3 -TiO 2 对 Cr 3+ 具有比较稳定 的吸附去除效率。溶液中 Na + 对 Cr 3+ 的吸附过程有一定的的抑制作用，Ca 2+ 的存在则会促进 Al 2 O 3 -TiO 2 对 Cr 3+ 的吸附。用 H 2 SO 4 溶液对已吸附了 Cr 3+ 的吸附剂进行脱附，脱附再生三次后，Al 2 O 3 -TiO 2 对 Cr 3+ 仍具有较高的吸附 能力。 （4）实际鞣制废水沉淀物对溶液中 Cr 3+ 的吸附 实际鞣制废水沉淀物的 XPS、XRD 及 FTIR 分析表明，沉淀物主要由 Al(OH) 3 ，Al 2 O 3 , ZrO 2 和一些有机物组成，烧结后变为 Al 2 O 3 , ZrO 2 和有机物。 沉淀物烧结前后对Cr 3+ 均具有一定的吸附效果，烧结后的沉淀物对Cr 3+ 的吸附量略有降低，对 Cr 3+ 的吸附为吸热反应。Cr 3+ 吸附过程可以用 Langmuir 方程和二级动力学方程进行很好的拟合。随着 pH 值的升高，Cr 3+ 的去除率逐渐增高，当 pH=7.0 时达到最大；Na + 、Ca 2+ 在吸附过程中与 Cr 3+ 产生竞争作用而降低 Cr 3+ 的吸附效率。 关键词，铝，锆，鞣制废水，Cr 3+ ，吸附III STUDY ON ADSORBENT PREPARATION OF NON-CHROME TANNING WASTEWATER PRECIPITATE AND ITS FEASIBILITY OF REMOVE CHROME ABSTRACT The chromium in the wastewater come mainly from tanning process, which was often removed and recycled by chemical precipitation. The removal of Cr 3+ can reach to about 98%, but there are still a small amount of chromium in the wastewater after precipitation. Therefore, the low concentration of chromium-containing wastewater after precipitation need to be further treated and reach to the national emission standard(Cr(VI)<0.1 mg/L, total chromium< 1.5 mg/L). There are some common methods to treat the low concentration of chromium-containing wastewater, such as ion exchange, membrane separation, activated carbon adsorption and so on. However, these methods are not suitable for application in the majority of our enterprise because of the higher costs. In recent years, a variety of cheap materials were used as adsorbents to remove the heavy metal in the wastewater. Some studies have shown that many biological wastes are very effective adsorbent, such as peanut hulls, fly ash, bark and so on. Currently, zirconium, alumium tanning and more metal binding tanning have gradually been used in the tanning of part vamp, clothing, sofa and light leather in the enterprise. There are some waste generated in this process and their main component is a variety of metal hydroxides. In this topic, zirconium, alumium, titanium oxide and hydroxide were simulated as the precipitate in non-chrome tanning wastewater. And they were modified or used as adsorbent directly to study the adsorption properties of Cr 3+ . The main adsorbent materials, such as Zr(OH) 4 , Al(OH) 3 , ZrO 2 , Al 2 O 3 -TiO 2 and precipitate in actual alumium tanning wastewater were synthesized, and above several materials were used as adsorbent, Cr 3+ was the target pollute. The adsorption characteristics of the above materials to Cr 3+ was studied, and some important conclusions are as follows.IV (1) Adsorption of Cr 3+ on Zr(OH) 4 and ZrO 2 The XRD analysis of Zr(OH) 4 shows that it can be completely converted into ZrO 2 after sintering at 500℃ for 3h. Zr(OH) 4 and ZrO 2 have a good adsorption effect to Cr 3+ , and the adsorption amount of Cr 3+ increases with the increasing of temperature, The adsorption isotherms at different temperature can fit with Freundlich model well, so the adsorption belongs to multilayer chemical adsorption. Under the experimental conditions, the adsorption amount of Cr 3+ on Zr(OH) 4 and ZrO 2 can reach up to 81.30mg/g and 126.7mg/g, respectively. The adsorption equilibrium was achieved at 60min. The adsorption kinetics obeyed pseudo-second-order equation at different initial concentrations; The adsorption efficiency of Cr 3+ reduced because of the competition between Cr 3+ and Na + , Ca 2+ in adsorption process. At pH<4.0，Cr 3+ is removed by adsorption, and when pH>4.0, Cr 3+ is removed by precipitation and adsorption. The SEM-EDS analysis of Zr(OH) 4 and ZrO 2 shows that the hydroxy on the adsorbent plays an important role in the adsorption process. (2) Adsorption of Cr 3+ on Al(OH) 3 Al(OH) 3 have obvious adsorption effect to Cr 3+ , the maximum adsorption amount of Cr 3+ is 49.29mg/g in the experimental Cr 3+ concentration at 25℃and the adsorption amount increases with the increasing of concentration of Cr 3+ . The adsorption belongs to multilayer chemical adsorption and the adsorption dynamics fitted the pseudo-second-order equation very well. pH has great influence on the adsorption process. The removal rate of Cr 3+ can reach to the maximum value at pH=7-8. The salt ion in the solution can restrain the adsorption, and the efficiency of Ca 2+ is more obvious. For the removal of Cr 3+ from the actual chrome tanning wastewater, the removal rate of Cr 3+ was lower than the rate of Cr 3+ solution when the Cr 3+ concentration and adsorbent dosage were same. (3) Adsorption of Cr 3+ on Al 2 O 3 -TiO 2 Al 2 O 3 -TiO 2 , Al 2 O 3 -ZrO 2 , ZrO 2 -TiO 2 were synthesized, and the adsorption properties of Cr 3+ were researched. Al 2 O 3 -TiO 2 has higher adsorption efficiency of Cr 3+ in the above adsorbents and the removal rate of Cr 3+ is relatively stable at pH=6-10. The Na + in the solution can restrain the adsorption, while the Ca 2+V will promote the adsorption. The loaded Cr 3+ Al 2 O 3 -TiO 2 can be desorbed in 0.1mol/L H 2 SO 4 solution, and after three desorption-regeneration cycles, the adsorption amount of Al 2 O 3 -TiO 2 does not significantly reduced. (4) Adsorption of Cr 3+ on precipitate from actual tanning wastewater The precipitate was produced by adding alkali from alumium tanning wastewater of a company in Taishan. The