Bioadsorbents

Bioadsorbents are adsorbent materials derived from biological sources or biomass that remove contaminants from liquids or gases by adsorption. They include raw or modified agricultural wastes (rice husk, banana peel), microbial biomass, algal biomass, and biopolymers such as chitosan, cellulose, and lignin, as well as biochars produced from biomass.

In water treatment, bioadsorbents target heavy metals (lead, cadmium, arsenic), dyes, phosphates, and various organic compounds. They are used in batch and fixed-bed column operations, often as a low-cost, sustainable alternative or complement to conventional adsorbents like activated carbon.

Adsorption mechanisms rely on surface functional groups, porosity, and the interaction between pollutant molecules and the adsorbent. Factors such as solution pH, contact time, initial pollutant concentration, temperature, and competing ions influence capacity.

Advantages include renewability, valorization of waste, and potential low cost. Challenges include variable feedstock composition, limited adsorption capacity, regeneration efficiency, and environmental impacts of regeneration. Research focuses on chemical or physical modification, synthesis of composites, magnetic bioadsorbents for easier separation, and use of biochars with enhanced surface area.

Examples of bioadsorbents are chitosan beads and films, alginate composites, cellulose-based powders, lignin-derived adsorbents, and activated biochar from agricultural residues.