The adsorption of the hydrogel can be divided into chemisorption and physisorption. Chemisorption is an irreversible process, mainly because its adsorbent and adsorbent are chemically bonded in the interaction水凝胶的吸附可分为化学吸附和物理吸附。化学吸附是一个不可逆的过程，主要是因为它的吸附剂和吸附剂在相互作用中是化学键合的; the destruction of the bond is permanent and, once destroyed, will not be able to bond again. In contrast, physisorption is an irreversible process, usually controlled by physical forces, such as hydrogen bonding, ionic bonding, π–π stacking, hydrophobic interactions, etc., and can be restored after being disrupted. In the preparation of hydrogels, physical action is usually combined with chemical action to strengthen their adsorption properties and mechanical properties, such as in self-healing hydrogels, which usually disperse energy consumption by physical action to ensure that the integrity of internal chemical bonds and mechanical properties is improved; such hydrogels are widely used in bioengineering ^[1]. In the preparation of hydrogels in the field of adsorption, researchers have also chosen to combine the two modes of action. The specific adsorption mechanisms and their classification are as follows.纽带的破坏是永久性的，一旦被破坏，将无法再次结合。相比之下，物理吸附是一个不可逆的过程，通常由物理力控制，如氢键、离子键、π-π堆积、疏水相互作用等，被破坏后可以恢复。在制备水凝胶时，物理作用通常与化学作用相结合，以加强其吸附性能和机械性能，例如在自修复水凝胶中，通常通过物理作用分散能量消耗，以确保内部化学键和机械性能的完整性得到改善;这种水凝胶广泛用于生物工程[39]。在吸附领域的水凝胶制备中，研究人员还选择将这两种作用模式结合起来。具体的吸附机理及其分类如下。

In the adsorption process, different functional groups have different adsorption mechanisms and different modes of action, and functional groups determine the type and strength of intermolecular forces and the chemical reactivity of molecules. The main functional groups involved in the adsorption process of polysaccharide-based hydrogel materials can be divided into three main categories: oxygen-containing functional groups, nitrogen-containing functional groups, and sulfur-containing functional groups. 在吸附过程中，不同的官能团具有不同的吸附机理和不同的作用方式，官能团决定了分子间力的类型和强度以及分子的化学反应性。多糖基水凝胶材料吸附过程中涉及的主要官能团可分为三大类：含氧官能团、含氮官能团和含硫官能团。N, O, and S class heteroatoms can contribute to one or more electrons and form coordination bonds with metal ions while also undergoing ion exchange or electrostatic attraction to achieve the adsorption of a wide range of contaminants. Among the various metal adsorption mechanisms reported for hydrogels, the three methods of electrostatic interactions, ion exchange, and surface complexation (including coordination and chelation) have been found to be closely related to surface functional groups ^[2]. As shown in Figure ，O和S类杂原子可以贡献一个或多个电子并与金属离子形成配位键，同时还进行离子交换或静电吸引以实现对各种污染物的吸附。在报道的水凝胶的各种金属吸附机制中，静电相互作用、离子交换和表面络合（包括配位和螯合）这三种方法被发现与表面官能团密切相关[6]。如图1, the process of action when adsorption is carried out by these three modes of action is depicted, among which most adsorption mechanisms of the two electrostatic interactions and ion exchange are reversible, and the adsorbents can be reused and belong to physical adsorption.所示，描述了通过这三种作用模式进行吸附时的作用过程，其中两种静电相互作用和离子交换的吸附机理大多是可逆的，吸附剂可以重复使用，属于物理吸附。

The pseudo-first-order kinetic model is based on the modal diffusion theory, which assumes that the arrival of the adsorbent from the solution to the adsorbent’s surface is controlled by the diffusion step and that the adsorbent’s surface has only one binding site ^[3]. The form of the equation is as follows:伪一级动力学模型基于模态扩散理论，该理论假设吸附剂从溶液到达吸附剂表面受扩散步骤控制，并且吸附剂表面只有一个结合位点[40]。等式的形式如下： where其中 q_t is the adsorption capacity at ti是时间T的吸附容量（me t (mg/g), g/g），q_e is the adsorption capacity at the 是吸附平衡时刻的吸附容量（moment of adsorption equilibrium (mg/g), and g/g），K₁ is the rate constant of the first-order kinetic.是一阶动力学的速率常数。

The pseudo-second-order kinetic model is based on the adsorption rate-limiting step and contains the adsorption mechanism, such as chemisorption, which involves electron sharing or electron transfers between the adsorbate and the adsorbent ^[5]. The conformity to the pseudo-second-order kinetic model indicates that adsorption kinetics are mainly controlled by chemical interactions rather than by the material transport steps. The form of the equation is as follows:伪二阶动力学模型基于吸附限速步骤，包含吸附机理，如化学吸附，涉及吸附物和吸附剂之间的电子共享或电子转移[42]。与伪二阶动力学模型的一致性表明，吸附动力学主要由化学相互作用控制，而不是由材料传递步骤控制。等式的形式如下： where其中 q_t is the adsorption capacity at ti是时间T的吸附容量（me t (mg/g), g/g），q_e is the adsorption capacity at the mo是吸附平衡时刻的吸附容量（ment of adsorption equilibrium (mg/g), and g/g），K₂ (（g/mg·h) is the pseudo-second-order rate constant.） 是伪二阶速率常数。

The Langmuir adsorption isotherm model is the most widely used molecular adsorption model, which can predict the maximum adsorption capacity of adsorbents by considering the influence of the adsorbent’s surface and temperature ^[6]. This theory is a single molecular layer adsorption theory, which requires a homogeneous solid surface with the same adsorption capacity and no interaction between the adsorbed molecules, but the assumptions of the model are far from the actual conditions, and the information obtained is sometimes highly inaccurate ^[7]. The form of the equation is as follows:吸附等温线模型是应用最广泛的分子吸附模型，它可以通过考虑吸附剂表面和温度的影响来预测吸附剂的最大吸附容量[43]。该理论是单分子层吸附理论，它要求具有相同吸附容量的均匀固体表面，并且吸附分子之间没有相互作用，但模型的假设与实际情况相去甚远，获得的信息有时非常不准确[44]。等式的形式如下： where其中 C_e is the equilibriu是溶液的平衡浓度，m concentration of the solution, mg/L, Q_e is the adsorption capacity at the moment of adsorption eg/L，quilibrium (mg/g), Q_m is the maximum adsorption capacity (saturation), 是最大吸附容量（饱和度）、mg/g, and 和 K_L is the 是与键合位点的亲和力和吸附能Langmuir constant related to the affinity and adsorption energy of the bonding site, L/g./g相关的朗缪尔常数。

The Freundlich isothermal adsorption equation is an empirical equation with no assumptions. The form of the equation is as follows:弗氏等温吸附方程是一个没有假设的经验方程。等式的形式如下： where其中 Qq_e is the adsorption a是吸附达到平衡时的吸附量mount, mg/g, when adsorption reaches equilibrium, g/g，C_e is the concentration of adsorbate in solution at adsorption equilibriu是吸附平衡时溶液中吸附物的浓度，m, mg/L, g/L，K_F is the constant related to adsorption capacity and adsorption strength under the Freundlich model, and 是弗氏模型下与吸附容量和吸附强度相关的常数，1/n is the Freundlich constant. A large value of K为弗氏常数。K 值大_F is a sign of a better adsorption performance of the adsorbent. Freund是吸附剂吸附性能更好的标志。弗氏吸附等温线可通过绘制lich adsorption isotherms can be obtained by plotting lnnq得到_e针对 against lnC_e at different temperatures ^[8].在不同温度下[45]。

Heavy metal ions are highly toxic, non-degradable, and bioaccumulative in the environment and circulate through the food chain in water and biological systems, seriously affecting the organisms at the top of the food chain ^[9][10]. Heavy metals are metals with a density greater than 重金属离子剧毒、不可降解，在环境中具有生物蓄积性，在水和生物系统中通过食物链循环，严重影响食物链顶端的生物[59，60]。重金属是密度大于4.5 g克/cm厘米的金属³, mainly including Au, Ag, Cu, Pb, Zn, Ni, Co, Cd, Hg, Cd, and more than ，主要包括金、银、铜、铅、锌、镍、钴、镉、汞、镉等40 other kinds of metals ^[11]. The five most toxic to humans are lead, mercury, chromium, arsenic, and cadmium. These heavy metals cannot be decomposed in water, and their toxicity is amplified when they enter the human body多种金属[61]。对人体毒性最大的五种是铅、汞、铬、砷和镉。这些重金属在水中不能分解，进入人体时毒性被放大; therefore, efficient and special methods are needed to remove heavy metal contaminants from water systems ^[12]. The adsorption process of heavy metal ions is directly related to the functional groups of the adsorbent materials themselves, and most current studies mainly revolve around the adsorption of divalent heavy metal ions, of which 因此，需要高效和特殊的方法来去除水系统中的重金属污染物[62]。重金属离子的吸附过程与吸附材料本身的官能团直接相关，目前的研究大多围绕二价重金属离子的吸附展开，其中Cu²⁺,， Pd钯²⁺, and Cd和镉²⁺ are predominant. Table 占主导地位。表1 summarizes the polysaccharide-based adsorbent materials in the last two years for this application of heavy metal ion adsorption.总结了过去两年多糖基吸附材料用于重金属离子吸附的应用。

There are many methods for removing dyes from wastewater: biological dye removal, acoustic chemical degradation, electrocatalytic degradation, cation exchange membrane technology, etc. However, these processes produce toxic residues that cause secondary pollution and are costly to implement. In contrast, the gel’s adsorption method is simple, efficient, and inexpensive to operate. Hydrogels have a strong dye removal capability, and dyes are more easily diffused in the dissolved hydrogel, which enhances the adsorption capacity via electrostatic interactions with oppositely charged dyes ^[39][85].

There is a wide range of adsorbed dyes, among which methylene blue (MB), malachite green (MG), and methyl orange (MO) fuels are more widely adsorbed. MB is a phenothiazine cationic dye, an alkali, that is used to treat methemoglobinemia in histology and microscopy to identify and detect bacteria, to treat fungal infections by staining tissues ^[40][21], and to stain cotton and wood. The waste dye discharged into the environment after use can be harmful, causing dizziness, headaches, tremors, and mental confusion, among other symptoms ^[41][86]. Malachite green (MG) is a toxic trityl methane chemical, both as a dye and as a bactericidal and parasiticidal chemical, is an alkali, and is prohibited for use in aquaculture. In industries, it is used to color leather, paper, cotton, and silk. However, it is potentially carcinogenic, teratogenic, and mutagenic and is difficult to remove from water ^[42][87]. Table 2 summarizes polysaccharide-based adsorbent materials used in the past two years for this application of dye adsorption.

In the treatment of contaminants in water, attention has been focused mainly on the adsorption of textile dyes and heavy metals. However, the harmful effects of these emerging contaminants, such as pesticides, herbicides, fungicides, pharmaceutical compounds, and personal care products, on the water environment cannot be ignored. Once the toxic substances of pharmaceutical and medical waste enter the soil, they will be adsorbed by the soil, pollute the soil, kill microorganisms and protozoa in the soil, and destroy the microecology in the soil, which in turn will reduce the soil’s ability to degrade pollutants. Furthermore, the acid, alkali, and salts in the substances will change the nature and structure of the soil, leading to the acidification, alkalization, and hardening of the soil, affecting the development and growth of plant roots, and damaging the ecological environment; meanwhile, many harmful drug pollutants can cause serious damage to the liver and nervous systems. Table 3 summarizes the polysaccharide-based adsorption materials used for antibiotic adsorption in the past two years.