Optimization of Formic Acid/Acetic Acid for Lignin Extraction in Talahib (Saccharum spontaneum L.) and the Analysis of the Adsorbent Properties of Lignin Towards Cu(II) and Pb(II) in Aqueous Solution

Abstract

In this paper, Talahib (Saccharum spontaneum L), was subjected to lignin extraction using Formic Acid/Acetic Acid Pulping. The effect of the formic acid/acetic acid/water ratio and the reaction time to the lignin yield was determined. It was found that increasing the concentration of formic acid decreased the lignin yield due to the formation of formate esters, which in turn decreased its reactivity to condense with other materials in the solution. In terms of reaction time, highest yield was observed at lowest cooking time due to the absence of recondensation reactions. Then, the pulp was subjected to further delignification using peroxyacid treatment, which aided in the isolation of any residual lignin left. The isolated lignin was characterized using UV-Vis and ATR-FTIR spectroscopy. Analysis of the adsorbent capability of lignin towards Cu(II) and Pb(II) showed % equilibrium removal amounts of 14.149 ± 0.227 % and 11.384 ± 0.572 %, respectively, both with an equilibrium contact time of 20 minutes. Through kinetic analysis, it was observed that both adsorption processes follow a pseudo-second order model, which means that the adsorption rate depends on the concentrations of both the metal cation and the lignin adsorbent. It also showed that the substrate uptake was greater with Cu(II) (0.330 ± 0.0082 mg/g lignin) compared to Pb(II) (0.262 ± 0.0159 mg/g lignin).