Abstract

The results of a study of the adsorption of zinc(II) and chromium(III) ions by zeolites modified by HCl are presented. According to the data of elemental analysis and electron spectroscopy, the zeolites contain at least 75% heulandite in their composition. The removal of aluminum ions from the tetrahedral framework of the sorbent formed by AlO₄ and SiO₄ occurs upon modifying the zeolites by HCl. This leads to the destruction of the main component, heulandite, and compaction of the silicate layer. The time of establishment of adsorption equilibrium in the zeolite–aqueous solution system is 90 min. The isotherms of adsorption of zinc(II) ions are obtained in a temperature range 298–318 K at pH 5.6–5.8. It is shown that the adsorption of zinc(II) ions increases with growing temperature. The isotherms of adsorption of chromium(III) ions are obtained in a temperature range 298–318 K at pH 7.6–7.9. It is found that the adsorption of chromium(III) ions decreases with increasing temperature. The differential heats of adsorption are calculated based on the isosteres of adsorption. The increase in the adsorption of chromium(III) ions is accompanied by a decrease in the differential heat of adsorption from 36.9 to 26.8 kJ/mol. This may be associated with the nonuniformity of the surface of the adsorbent, due to what the metal ions are adsorbed on less active regions of the surface as far as the growth in the saturation of more active sites. The change in the differential heat of adsorption of zinc(II) ions with the growth in the degree of filling of the surface has a nonmonotone character. In the region of low degrees of filling of the surface, the differential heat of adsorption decreases, and then increases, which is probably determined by polymolecular adsorption presuming the presence of an adsorbate–adsorbate interaction. The efficiency of treatment of industrial wastewaters of the electroplating industry in the case of the use of the modified zeolites is over 97%.

中文翻译：

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改性沸石对锌（II）和铬（III）离子的吸附

摘要

给出了用HCl改性的沸石吸附锌（II）和铬（III）离子的研究结果。根据元素分析和电子光谱学的数据，这些沸石的组成中至少含有75％的辉石。从由AlO ₄和SiO ₄形成的吸附剂的四面体骨架中去除铝离子在用HCl改性沸石时发生。这导致主要成分赤铁矿的破坏，以及硅酸盐层的压实。在沸石-水溶液系统中建立吸附平衡的时间为90分钟。锌（II）离子的吸附等温线是在pH 5.6-5.8的298-318 K的温度范围内获得的。结果表明，锌（II）离子的吸附随着温度的升高而增加。在pH值为7.6-7.9的298-318 K的温度范围内可获得铬（III）离子的吸附等温线。发现随着温度的升高，铬（III）离子的吸附降低。吸附的差热是根据吸附的等排线计算的。铬（III）离子的吸附量增加，同时吸附的差热从36.9降低到26.8 kJ / mol。这可能与吸附剂表面的不均匀性有关，这是由于金属离子被吸附在表面的活性较低的区域上，直到活性较高的位置的饱和度增加为止。锌（II）离子的吸附差热随表面填充度的增加而变化，具有非单调特性。在表面填充度较低的区域中，吸附的差热先降低后升高，这可能是由多分子吸附（假定存在被吸附物-被吸附物相互作用）决定的。