Lignin extraction from barley straw using ultrasound-assisted treatment method for a lignin-based biocomposite preparation with remarkable adsorption capacity for heavy metal.

In this study, lignin was extracted using ultrasonic and then, by the gelation-solidification method, the extracted lignin was used as reinforcement for the synthesis of a novel biocomposite as biosorbent for removal of lead heavy metal from aqueous solutions. The structural and chemical characteristics of biocomposite were determined by FESEM, EDX, FTIR, and BET analyses, respectively. Biocomposite beads were used as an efficient adsorbent in the lead removal process from aqueous solutions in different conditions. Also, point zero charge studies and the effective parameters on adsorption such as contact time, pH, temperature and initial concentration, kinetics, isotherms, and thermodynamics of the adsorption, and adsorbent regeneration and reuse were investigated. The maximum adsorption capacity of the adsorbent was obtained 344.83 mg/g at C = 210 mg/L, T = 328 K, and pH = 5. The experimental kinetic and equilibrium data were well adjusted with pseudo-second-order kinetic models and Langmuir and Temkin isotherm models, respectively, according to linear regression (R), chi-square statistic (χ), and the sum of the squares of the errors (SSE). The thermodynamics parameters were analyzed and the results showed an endothermic and spontaneous adsorption process. Regeneration and reuse results of the synthesized biocomposite represented highly adsorption efficiency after five adsorption cycle stages.