Preparation of cross-linked magnetic chitosan particles from steel slag and shrimp shells for removal of heavy metals

In this study, a new method for preparation of cross-linked magnetic chitosan particles (MCPs) from steel slag and shrimp shells using green tea extract as crosslinking reagent has been presented. The MCPs obtained were characterized by means of X-ray diffraction analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy and magnetic properties, and then were used to investigate the adsorption properties of Cu(II) and Ni(II) ions in aqueous solutions. The influence of experimental conditions such as contact time, pH value, adsorbent dose and initial metal concentration, and the possibility of regeneration were studied systematically. The Cu(II) and Ni(II) adsorption isotherms, kinetics and thermodynamics have been measured and discussed. The results show that the synthesized MCPs have high adsorption capacity for both metal ions (126.58 mg/g for Cu(II) and 66.23 mg/g for Ni(II)), and have excellent regeneration stability with efficiency of greater than 83% after five cycles of the adsorption–regeneration process. The adsorption process of Ni(II) and Cu(II) on MCPs was feasible, spontaneous and exothermic, and better described by the Langmuir model and pseudo-second-order kinetic equation. The MCPs can be applied as a low cost and highly efficient adsorbent for removal of heavy metals from wastewater due to its high adsorption capacity, easy recovery and good reusability.本研究提出了一种以绿茶提取物为交联剂，以钢渣与虾壳为原料制备交联磁性壳聚糖微球（cross-linked magnetic chitosan particles, MCPs）的新方法。对所制备的MCPs采用X射线衍射分析、傅里叶变换红外光谱法、扫描电子显微镜及磁性能表征手段进行了物性表征，随后将其用于探究水溶液中铜(II)与镍(II)离子的吸附性能。系统考察了接触时间、pH值、吸附剂投加量、初始金属离子浓度等实验条件对吸附过程的影响，并探究了其再生可行性。研究测定并讨论了铜(II)与镍(II)的吸附等温线、动力学及热力学参数。结果表明，所合成的MCPs对两种金属离子均具备较高的吸附容量（铜(II)为126.58 mg/g，镍(II)为66.23 mg/g），且经过五次吸附-再生循环后仍可保持83%以上的吸附效率，展现出优异的再生稳定性。MCPs对镍(II)与铜(II)的吸附过程具备可行性、自发性且为放热过程，其吸附行为更符合朗缪尔模型与准二级动力学方程的拟合结果。鉴于其高吸附容量、易于回收且可重复利用的特性，MCPs可作为一种低成本、高效率的吸附剂用于废水中重金属的去除。