The role of surface functional groups of pectin and pectin-based materials on the adsorption of heavy metal ions and dyes

Natural macromolecules have been used to adsorb pollutants including heavy metal ions and organic dyes due to low-cost, accessible, biodegradable, and eco-friendly advantages. Pectin, an important natural polymer, possesses abundant carboxyl and hydroxyl functional groups that can interact with the metal and organic cations via electrostatic interaction; as well as be modified by other chemicals for preparing hybrid and composite materials. The resultant materials have been employed to remove pollutants from aqueous solution; the importance of chemical composition was unlocked. Here, we reviewed contaminant removal by pectin, and pectin-based hybrid and composite materials, and highlighted the role of functional groups on pollutant removal. The removal of heavy metal ions was mainly due to surface coordination, while that of organic cations to electrostatic interactions of the functional groups. Moreover, the influence of initial contaminant concentration was critically discussed. The comprehensive review can provide valuable information on pectin and its application in contaminant removal.