Sodium lignosulfonate: a renewable corrosion inhibitor extracted from lignocellulosic waste

In this study, sodium lignosulfonate was extracted from a natural lignocellulose waste and its characterization and potential application as a corrosion inhibitor were investigated. FTIR results confirmed presence of sulfonic groups like ones in a commercial sample. The aqueous solubility of sodium lignosulfonate increased from 29.17 to 88.58 wt% when reaction time was increased from 1 to 4 h. Corrosion inhibition efficiency of 90.23% was obtained. The main factors of lignin concentration (10–25 g/L), temperature (80–140 °C), reaction time (1–4 h), sodium hydroxymethyl sulfonate/lignin mole ratio (0.3–1.2), and sodium hydroxide concentration (0.25–1 M) were investigated for their effect towards the aqueous solubility of sodium lignosulfonate. The Taguchi orthogonal array statistical design was used to investigate effects of factors, their interactions, and the optimum values within factor levels towards solubility as the response. The solubility of the sodium lignosulfonate was found to be more significantly influenced by reaction time > lignin concentration > sodium hydroxide > temperature > reactants/lignin ratio. The optimum condition for sulfomethylation reaction was found to be 4 h, 100 °C, 25 g/L, 0.9, and 0.5 M for reaction time, temperature, lignin concentration, reactant/lignin ratio, and NaOH concentration, respectively. The corrosion test revealed a reduction in corrosion rate from 2.6 to 1.2 mm/year when the concentration of the sodium lignosulfonate was increased from 0 to 8 ppm.