Biocomposites Made from Cocos nucifera L. Fibres and Polyhydroxybutyrate (PHB) for Water Treatment Applications

Cr(VI) is considered one of the most dangerous pollutants due to its bioaccumulation and toxicity, which has driven the search for sustainable and effective solutions for its removal from wastewater. In this regard, the aim of this research was to develop a material based on cellulose acetate (CA) extracted from Cocos nucifera L. fibres and polyhydroxybutyrate (PHB) for the removal of Cr(VI). The biocomposite (PHB/CA) was synthesised using the casting method; its adsorption capacity was evaluated in batch systems and its efficiency measured at different contaminant concentrations. The characterisation results indicated interactions between the fibres and the PHB, resulting in a porous material containing hydroxyl, amino, ether/alcohol, carbonyl and alkane/alkyl functional groups. Cr(VI) removal tests indicated that the optimal operating conditions were achieved at a pH of 3 and a concentration of 15 mg/L, yielding an adsorption efficiency of 44.5%, and showing a trend consistent with the Elovich kinetic model and the Langmuir isotherm. In conclusion, this research proposes the exploration of new bioadsorbents derived from coconut agro-industrial waste combined with biopolymers for the remediation of contaminated water, thereby expanding our understanding of the relationship between the structure of bio-composites of renewable origin and their performance in heavy metal adsorption processes.