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Amine functionalized lignin has been prepared from enzymatic hydrolysis residue (EHR) obtained from corncob furfural production process by using the Mannich reaction. Dehydration of EHR with phosphoric acid (H 3 PO 4 ) has been employed to enhance its reactivity for amine functionalization. For amine functionalization of dehydrated lignin (DEHL), hexamethylenediamine (HDMA) and diethylamine (DEA) have been used as amine sources, while furfural has been used as an aldehyde source. The structural changes during the dehydration and amine functionalization processes were elucidated using proximate analysis, elemental analysis, FTIR, SEM, EDS, BET, and XPS analysis. The Mannich reaction conditions were optimized to obtain amine functionalized lignin (AEHL) with a high N content. Amine type and the Mannich reaction temperature were found to be the most influential factors affecting N content. Optimized AEHL exhibited the highest N content of 7.04%. The adsorption performance of the optimized AEHL was evaluated for the adsorption of reactive yellow dye (RYD-145). The effect of various factors, including adsorbent dosage, pH, temperature, time, and initial dye concentration, on removal efficiency was evaluated. The maximum adsorption capacity of AEHL for RYD-145 was found to be 37.52 mg/g following Langmuir and pseudo-second order kinetics.
Waseem et al. (Mon,) studied this question.