Removal of Lignin from Wastewater Using an Industrial Waste as Adsorbent: A Statistical and Kinetic Modeling Approach

Abstract

Lignin and its derivatives are identified as the prime pollutants in the effluents of many industries such as rice mill, paper, and pulp, which subsequently create dark coloration and toxicity to the aquatic bodies when they release without treatment. The present study focuses on the removal of lignin from aqueous solutions using an industrial by-product, dolochar as an adsorbent. The adsorbent material (before and after adsorption) was characterized with the help of SEM and EDS studies. The pseudosecond-order kinetic model with the regression coefficient (R2) of 0.99 has well defined present study of the lignin adsorption process using dolochar. For the evaluation of response surface methodology through the Box–Behnken design (BBD) technique, three input variables: adsorbent dose (4–8 g/L), contact time (60–120 min), and pH (6–10) were selected. The effect of these chosen variables was verified by conducting a total number of 15 experiments in a multivariate system for the removal of lignin through dolochar. The quadratic polynomial model has yielded the regression coefficient (R2) of 0.99 when the experimental data fitted to it, which is indicating the suitability of the model for the process. The precision and efficiency of the model were visualized using the ANOVA and lack of fit test. The process has resulted: adsorbent dose 6.21 g/L, contact time 85.15 min, and pH 7.78 as optimized parameters for the removal of lignin using the industrial by-product dolochar.