In this study, we have developed a simple technique to prepare cationic chitosan hydrogel with interconnected porous structure using freeze–thaw process and the obtained hydrogel was named FCS hydrogel. Scanning electron microscopy (SEM) imaging discovered that the synthesized hydrogel demonstrated interconnected porous structure in the scope of 5–20 μm. We also showed that the FCS hydrogel exhibits pH responsiveness behavior, and demonstrated reversible swelling and de-swelling behaviors maintaining their mechanical stability. We demonstrate that the FCS hydrogel swelling capacity decreased at alkaline pH and rose with a decline in pH value. Besides, the FCS hydrogel presented specific surface area of 78.25 ± 8.75 m² g⁻¹, due to the cryogenic treatment of glutaraldehyde cross-linked chitosan hydrogel could increase the surface area and permeability of composite hydrogel and then strongly increasing the adsorption capacity. Subsequently, the FCS monolithic hydrogel tested dyes removal, which provides a high removal efficiency towards anionic dyes including congo red (CR) and sodium fluorescein (SFL) dyes. Significantly, we show that the FCS hydrogel could be regenerated and reused as an adsorbent for wastewater treatment without significant loss of pollutants removal efficiency over a number of adsorption and washing cycles. This study offers a promising environmental friendly and sustainable interconnected porous hydrogel for anionic dye removal from wastewater.

在这项研究中，我们开发了一种使用冻融工艺制备具有互连多孔结构的阳离子壳聚糖水凝胶的简单技术，并将所得水凝胶命名为FCS水凝胶。扫描电子显微镜 (SEM) 成像发现，合成的水凝胶在 5-20 μm 范围内表现出相互连接的多孔结构。我们还表明，FCS 水凝胶表现出 pH 响应行为，并表现出可逆的溶胀和去溶胀行为，从而保持其机械稳定性。我们证明 FCS 水凝胶的溶胀能力在碱性 pH 值下降低，并随着 pH 值的下降而上升。此外，FCS 水凝胶的比表面积为 78.25 ± 8.75 m ²  g ^-1，由于戊二醛交联壳聚糖水凝胶的低温处理可以增加复合水凝胶的表面积和渗透性，从而大大增加吸附能力。随后，FCS 整体水凝胶测试了染料去除率，它对包括刚果红 (CR) 和荧光素钠 (SFL) 染料在内的阴离子染料提供了高去除率。重要的是，我们表明 FCS 水凝胶可以再生并用作废水处理的吸附剂，而在许多吸附和洗涤循环中不会显着降低污染物去除效率。该研究为从废水中去除阴离子染料提供了一种有前途的环境友好且可持续的互连多孔水凝胶。