Nanochitosan-based adsorbents for sustainable treatment of palm oil mill effluent

Palm oil mill effluent (POME) is a highly contaminated wastewater resulting from palm oil processing, characterized by high levels of organic matter, suspended solids, oil and grease, and intense color. The improper release of untreated or inadequately treated POME leads to serious environmental issues, including water pollution, oxygen depletion in aquatic systems, and ecological harm. Traditional treatment methodologies, such as ponding systems, anaerobic digestion, and coagulation-flocculation, face numerous challenges like long treatment times, extensive land use, secondary sludge production, and inconsistent pollutant removal rates. Recently, nanotechnology has surfaced as an innovative treatment solution, with nanochitosan, a nanosized variant of the biopolymer chitosan, attracting attention for its large surface area, abundant amino groups, strong adsorption capacity, biodegradability, and environmental friendliness. This review examines synthesis techniques for nanochitosan (ionic gelation, microemulsion, precipitation), linking their structure-property relationships to pollutant removal mechanisms. A comparison between bulk and nanochitosan emphasizes how increased surface area and functional group richness enhance adsorption capability and treatment efficiency. The efficacy of nanochitosan in eliminating organic pollutants, suspended solids, oils, color compounds, and heavy metals from POME is highlighted. The integration of nanochitosan with conventional biological and physicochemical treatments is also examined to boost treatment performance and sustainability. Moreover, challenges related to large-scale applications, regeneration, economic factors, and possible environmental impacts are discussed. Overall, nanochitosan-based treatment systems show promising potential as sustainable, effective solutions for POME remediation, contributing to advancements in eco-friendly wastewater management technologies.