重金屬不可生物降解且易在環境中積累，會對環境造成嚴重污染。同時，重金屬離子可以通過食物鏈進入人體，導致不同種類的疾病。在許多重金屬離子中，Hg²⁺，Cd²⁺的毒性更大。因此，去除廢水中的Hg²⁺和Cd²⁺非常重要。表面吸附技術是最普遍、使用最廣泛的重金屬脫除技術，具有環保、成本低、操作簡便、可再生等優點。最近，納米技術正在應用于吸附法，以提高其去除重金屬離子的效率。

"沸石咪唑酯骨架結構材料"(ZIFs)是多孔晶體材料，在其中，有機咪唑酯交聯連接到過渡金屬上，形成一種四面體框架。這種籠狀結構可選擇性地高效捕獲和存儲客體分子。Fe₃O₄作為一種磁性納米粒，可利用外加磁場實現吸附材料的有效分離。此外，半胱氨酸的巰基可可與Hg²⁺高效螯合，實現對Hg²⁺有效的抓取。基于這些特性，中科院寧波材料所的吳愛國研究員及張玉杰副研究員提出利用Fe₃O₄納米粒表面修飾聚丙烯酸（PAA）后與ZIF-90通過自組裝形成核殼結構納米粒，合成過程如Scheme 1所示。引入聚丙烯酸的目的主要有：阻止Fe₃O₄納米粒聚集、利用PAA的羧基與ZIF-90中的Zn²⁺相互作用穩定納米粒。隨后利用亞胺鍵引入半胱氨酸，構建可高效吸附Hg²⁺的新型雜化納米材料Fe₃O₄@ZIF-90-Cysteine。

Scheme 1. 新型雜化納米吸附材料Fe₃O₄@ZIF-90-Cysteine的制備過程

Title：A novel hybrid nanoadsorbent for effective Hg²⁺adsorption based on zeoliticimidazolate framework (ZIF-90) assembled onto polyacrylic acid capped Fe₃O₄ nanoparticles and cysteine

Abstract

This research reports a newmercury adsorbent in which Fe₃O₄ as a core wasembedded into the shell of ZIF-90 in a one-pot synthesis and the subsequent postsynthesis modification (PSM) of its surface with cysteine covalently, via aSchiff’s base reaction. Poly acrylic acid (PAA) was capped on the surface ofnanoparticles to prevent agglomeration of the nanoparticles. In addition, -COOHgroups of PAA coordinated with Zn²⁺ of ZIF-90 and this providedthe platform for ZIF-90 to grow on the nanoparticles forming the core-shellstructure. Based on the strong interactions between the thiol groups on theadsorbent and mercury ions as elucidated by the XPS analysis, theas-synthesized adsorbent showed selectivity for Hg²⁺. The sorbentexhibited high adsorption capacity of 900mgg^-1 towards Hg²⁺ as calculated at pH 4and the adsorption kinetics followed pseudo-second-order kinetics model better.The Hg²⁺ loaded adsorbent was easily regenerated and itmaintained about 70% efficiency after the third use. Low-cost, readilyavailable and green materials, facile preparation, efficient removal and thebreakthrough in three times recyclability give the novel ZIF-90 based hybridnanoadsorbent wide prospects in the field of environmental remediation as agood adsorbent for Hg²⁺ removal in wastewater.