A novel multifunctional composite adsorbent which possesses the ability for anion exchange and toxic metal complexation has been synthesized by the hybridization of layered double hydroxides (LDH) and fulvic acid (FA) in this study. The results show that FA with lots of functional groups can be effectively and stably anchored on the surface of LDH through coagulation process without occupying the interlayer of LDH. Therefore, the anion exchange ability remains and the adsorption capacity of Orange II can reach 1.9 mmol/g, which is almost as much as stoichiometric anion exchange capacity of pure LDH. Moreover, the composite adsorbent’s adsorption capacity of Cu²⁺, Pb²⁺, Ni²⁺ and Cd²⁺ can also get to 2.25 mmol/g, 0.98 mmol/g, 0.99 mmol/g and 0.16 mmol/g respectively with an adsorption preference order of Cu²⁺ > Pb²⁺ > Ni²⁺ > Cd²⁺. In addition, Orange II and toxic metals are able to be simultaneously removed by this composite adsorbent, and the adsorption of toxic metals can be enhanced by the synergetic adsorption of Orange II. Anion exchange with Cl⁻ in LDH matrix accounts for the adsorption of Orange II, while the adsorption of toxic metal is mainly attributed to the complexation of carboxyl functional group derived from FA.

中文翻译：

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黄腐酸固定层状双氢氧化物：一种多功能复合吸附剂，用于去除阴离子染料和有毒金属

通过层状双氢氧化物（LDH）和富里酸（FA）的杂交，合成了一种新型的具有阴离子交换和有毒金属络合能力的多功能复合吸附剂。结果表明，具有大量官能团的FA可以通过凝固过程有效而稳定地锚定在LDH表面，而不会占据LDH的中间层。因此，保留了阴离子交换能力，Orange II的吸附容量可达到1.9 mmol / g，几乎与纯LDH的化学计量阴离子交换容量相当。此外，复合吸附剂对Cu 2 ⁺，Pb 2 ⁺，Ni ²⁺和Cd ²⁺的吸附能力铜的吸附优先级也分别为2.25 mmol / g，0.98 mmol / g，0.99 mmol / g和0.16 mmol / g，吸附优先级为Cu ²⁺  > Pb ²⁺  > Ni ²⁺  > Cd ²⁺。另外，通过该复合吸附剂能够同时除去橙II和有毒金属，并且通过橙II的协同吸附可以增强有毒金属的吸附。有Cl阴离子交换^-中LDH基质占橙II的吸附，而有毒金属的吸附主要归因于来自FA衍生羧基官能团的络合。