AbstractThe presence of dissolved organic matter, scientifically known as humic substances, gives an undesirable color and taste to water. In addition, they are the precursors of carcinogenic disinfection by-products upon disinfection treatment. Adsorption provides a potential means of removal of humic substances, and lignocellulosic biomass serves as a promising candidate. In this paper, we report the application of modified coconut copra residues for adsorption of humic substances from peat swamp runoff. The FTIR spectra suggest that coconut copra residues are genuinely rich with carboxyl groups with long alkyl chains; this renders the material a natural biosorbent, attaining an average of 50% removal under the conditions of testing. Upon treatment, dissolution of lignin and hemicellulose with the enhancement of effective carboxyl groups occurs, improving the adsorption efficiency to 96%; the treated water is visibly clear. The relative band abundance and band shifts further confirm the involvement of the surface functional groups in the adsorption process. The modified coconut copra residue is an attractive biosorbent option for removal of humic substances. The operating conditions are mild, involving non-toxic chemicals, and no pH adjustment is necessary to allow adsorption.