Industrial wastewater has imposed increasing threats due to the large concentrations of various toxic and hazardous contaminants. Amongst various processes to treat wastewater, adsorption is widely being adopted due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, cost-efficiency, etc. Chitosan, the second most abundant biopolymer is well-known due to its unique properties and versatile nature like abundance, biodegradable, low-cost, presence of adsorptive functional groups, and good reactivity. Due to these properties, it is found highly potential for the application as an adsorbent to remove heavy metal ions. The present review study focuses and analyses the suitability of chitosan as an adsorbent for heavy metal removal, modifications of chitosan like cross-linking, grafting, & magnetic chitosan, the adsorption performance of chitosan and modified chitosan towards heavy metal ions along with the factors affecting it, kinetic model fitting, thermodynamic model fitting, and the isotherm fitting. The mechanism of adsorption is discussed in detail. Usage of a few novel modifiers has been highlighted. At last, the gaps in the research and future perspectives are discussed. Throughout the review, it was verified that chitosan upon chemical modifications with different physical morphologies showed good removal efficiencies and adsorption capacities for heavy metal for the synthetic wastewater due to the amino and hydroxyl functional groups which majorly took part in adsorption. Good removal efficiencies of greater than 80% were mostly obtained, with a few having extraordinary 95–96% uptake. Finally, gaps were observed in dynamic or column-based experiments and the complex industrial wastewater treatment which requires more focus to build an industrial perspective. Thus, the commercialization of modified chitosan adsorbent is quite far.

由于各种有毒和有害污染物的浓度很高，工业废水的威胁日益增加。在各种处理废水的方法中，由于其简单性，良好的处理效率，多种吸附剂的可获得性，成本效益等优点，吸附被广泛采用。壳聚糖是第二大生物聚合物，因其独特而广为人知。性质和多功能性质，例如丰度，可生物降解，低成本，存在吸附性官能团和良好的反应性。由于这些性质，发现其作为去除重金属离子的吸附剂具有很高的应用潜力。本综述研究重点和分析了壳聚糖作为吸附剂用于重金属去除，壳聚糖改性（如交联，接枝和磁性壳聚糖）吸附剂的适用性，壳聚糖和改性壳聚糖对重金属离子的吸附性能及其影响因素，动力学模型拟合，热力学模型拟合和等温线拟合。详细讨论了吸附机理。一些新颖的修饰符的用法已被强调。最后，讨论了研究的不足和未来的展望。在整个综述中，证实了壳聚糖经过化学修饰后，具有不同的物理形态，由于氨基和羟基官能团主要参与了吸附，因此对合成废水显示出良好的去除效率和对重金属的吸附能力。多数情况下可获得良好的去除效率，大于80％，少数几个具有95-96％的出色吸收率。最后，在基于动态或基于色谱柱的实验以及复杂的工业废水处理中观察到了差距，这需要更多的关注来建立工业视野。因此，改性壳聚糖吸附剂的商业化还很遥远。