镍铁类水滑石对偶氮阴离子染料的吸附脱色作用

采用镍铁类水滑石作为吸附剂,对偶氮阴离子染料酸性大红G、活性艳红X-3B和直接耐酸大红4BS废水进行脱色处理,研究了时间、镍与铁的物质的量之比、初始pH和无机电解质添加剂等因素对脱色率的影响,并结合红外光谱和X射线衍射分析结果讨论了其吸附脱色机理.结果表明,三种染料在镍铁类水滑石上的吸附均为层间的阴离子交换吸附和外表面的吸附.通过阴离子交换进入层间后,不同于直接耐酸大红4BS阴离子,酸性大红G和活性艳红X-3B两种阴离子与水滑石层间水分子之间产生氢键作用;在化学键合过程中,染料分子被镍铁类水滑石表面Fe3+氧化,同时偶氮键断裂导致脱色.

Adsorption performance and discoloring behavior of nickel-iron hydrotalcite-like compound for azo anionic dyes

Wastewater containing azo anionic dyes such as acid red G, reactive brilliant red X- 3B, and direct anti-acid red 4BS was decolorized with Ni-Fe hydrotalcite-like compound as the sorbent. The effects of time, Ni/Fe molar ratio, initial pH value and ionic electrolyte （dis- solved NaC1） on the removal rate of the three kinds of azo dyes were investigated; and the ad- sorption and decoloring mechanisms of the sorbent were discussed in relation to infrared spec- trometric data and X-ray diffraction data. It was found that the adsorption of the three kinds of azo dyes onto Ni-Fe hydrotalcite-like compounds is dominated by the anion exchange in the in- terlayer space and the adsorption on the external surface. Differing from direct anti-acid red 4BS anion, the anions of acid red G and reactive brilliant red X-3B, after entering the interlayer space of Ni-Fe hydrotalcite-like compounds by way of anion exchange, can link interlayer water molecules of Ni-Fe hydrotalcite-like compounds via hydrogen bonding. Besides, in the process of chemical binding, electron transfer occurs between the dye molecules adsorbed on the surface of Ni-Fe hydrotalcite-like compounds and Fe3＋ centre of Ni-Fe hydrotalcite-like compounds sur- face, which leads to breakage of azo bond thereby initiating decoloring.