Polydopamine functionalized superhydrophilic coconut shells biomass carbon for selective cationic dye methylene blue adsorption

Environmentally benign, high adsorption efficiency and high selectivity adsorbents are satisfied real demand in wastewater treatment. Coconut shell (CS), the agricultural and forestry biomass was applied to further modified with NaOH chemical activation, pyrolysis, and then surface modification with polydopamine (PDA). NaOH activation and heated in 600 °C rendered to carbon materials with high specific surface area in carbon skeleton. Dopamine was self-polymerization on the biomass carbon materials to form superhydrophilic and surface-adhering PDA coating which made the composites well dispersed in soluble dyes solutions and simultaneously introduced thiol- and/or aminoterminated molecules. Different initial concentrations, pH and temperatures were discussed in detail herein. Increasing nitrogen-containing or oxygen-containing groups can enhance the adsorption efficiencies for dyes in low MB concentrations. The uptake of MB maintains 100% adsorption efficiency when pH is 12. The charge selective adsorption of CS-NaOH@PDA adsorbent was applied to adsorb other cationic dyes in aqueous solution. The as-prepared CS-NaOH@PDA composites from waste biomasses showed superior adsorption capability for cationic dyes and excellent removal rate and importantly were environmentally friendly, revealing its promising potentials in low-cost adsorbents for authentic wastewater treatment applications.