A new, low-cost adsorbent: Preparation, characterization, and adsorption behavior of Pb(II) and Cu(II)

Abstract

This work aimed to develop waste (i.e., sulfonated lignin) application in simulated wastewater treatment. Sulfonated lignin (LS), a byproduct of the paper industry, was intercalated into a parent host of layered double hydroxides (LDH) by swelling–restacking method. X-ray diffraction patterns of the composite confirmed that long-chain LS anions exited in the interlayer of Mg2Al–LDH in two forms: (1) a “flat” form with d003=0.88nm; and (2) a “vertical” form with d003=9.08nm. Results showed that the obtained Mg2Al–LS–LDH composite was highly selective and efficient for the removal of Pb2+ and Cu2+, especially Pb2+, compared with the NO3–LDH precursor. The coexisting cations decreased the removal efficiency of Pb2+ or Cu2+ on Mg2Al–LS–LDH composite, which could be ascribed to outer-sphere sorption style, and the effect order of cations is Li+>Ca2+>K+>Na+. The pseudo-second-order model appropriately described the sorption kinetics of Mg2Al–LS–LDH composite for Pb2+ and Cu2+. Sorption isotherms for Pb2+ and Cu2+ by the Mg2Al–LS–LDH composite were found to be more satisfactorily fitted by the Langmuir model than by the Freundlich one. With increased Pb2+ or Cu2+ concentration from 2ppm to 200ppm, the maximum absorption capacity of the composite toward Pb2+ was ∼123mg/g and that toward Cu2+ was ∼64mg/g. Therefore, a new, low-cost adsorbent was synthesized by utilizing the byproduct LS, which may be a potential remedy for Pb2+ or Cu2+ in contaminated water.