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Lignin–poly(N-methylaniline) (lignin–PNMA) nanocomposites were synthesized via a chemical oxidative polymerization of N-methylaniline in the presence of enzymatic hydrolysis lignin (EHL). The lignin–PNMA composite consists of well size-distributed particles of 68.3 nm in mean diameter. This nanocomposite was further used as a novel sorbent for silver ions from aqueous solution. The lignin–PNMA nanocomposite particles exhibited excellent an adsorption property of silver ions compared to those of poly(N-methylaniline) and EHL. The saturated capacity of silver ions onto the lignin–PNMA nanocomposites was up to 1556.8 mg g–1 at 30 °C. Characterization results of the sorption product, i.e., lignin–PNMA nanocomposite particles after sorption, revealed that silver nanoparticles were achieved on the surface of lignin–PNMA nanocomposite particles. The results indicated that lignin–PNMA nanocomposites can be effectively used as a reactive sorbent to remove and recover silver ions from aqueous solution.

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Citric acid modified mixed hardwoods powder (CMH) was prepared as a biosorbent to remove copper ions and methylene blue (MB) from aqueous solution by batch techniques. FT-IR and XRD were used to characterize the biosorbent. The effects of initial pH value, biosorption temperature, contact time, and initial adsorbate concentration on the biosorption capacities and adsorptivity of Cu 2+ and MB onto CMH were investigated. The results showed that CMH exhibited excellent biosorption characteristics for Cu 2+ and MB. The maximal biosorption capacity of Cu 2+ and MB onto CMH was 165.0 and 237.4 mg/g at 20 °C, respectively. The biosorption kinetics studies indicated that Cu 2+ and MB biosorption followed the pseudo-second-order model. The biosorption may be controlled by external intraparticle diffusion mass transfer during the whole biosorption process. Furthermore, the biosorption-equilibrium can be well described by Langmuir and Freundlich isotherm models.

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