Simultaneous oxidation and esterification of cellulose for use in treatment of water containing Cu(II) ions

•Cellulose was modified using octenyl succinic anhydride and sodium hypochlorite.•Intrinsic viscosity varied with degree of substitution according to power law.•Adsorption capacity of cellulose for Cu(II) ions was increased on modification.•Adsorption was spontaneous at room temperature. Cellulose powder was modified with Sodium Hypochlorite (NaOCl) and Octenyl Succinic Anhydride (OSA) in different proportions. The adsorbents were characterised by BET, FTIR, XRD, TGA and SEM. Intrinsic viscosity increased with degree of substitution (DS). FTIR peaks confirmed the presence of carbonyl groups. Batch adsorption parameters studied were contact time, adsorbent dosage, pH and temperature. Adsorption process was influenced significantly by pH. Freundlich isotherm showed a better correlation coefficient (R2 and χ2) than Langmuir and Temkin isotherms. The adsorption process was inferred as physico-chemical adsorption process (based on isotherm and kinetic modelling). Pseudo second order kinetics model was found to fit well on the empirical data obtained. Adsorption of Cu(II) ions over the modified cellulose was found to be exothermic in nature (ΔH