Malachite Green Dye Removal in Water by Using Biochar Produced from Pinus patula Pellet Gasification in a Reverse Downdraft Reactor

The efficiency of the elimination of malachite green dye (MG) in water was investigated using biochar (BC) obtained from Pinus patula wood pellets (BC-WP). The biomass was gasified, reaching a temperature of 391.07 °C near the reactor wall. During the adsorption tests, three independent factors were considered: the solution pH, BC concentration, and the BC particle size, which were optimized using different study ranges (4–10, 6–12 g/L, and 150–600 μm, respectively) at 30 min of contact time. The response surface methodology was used through a face-centered central composite design for this purpose. The experimental results were analyzed to develop a quadratic regression model that fitted the experimental data achieved. The highest removal percentage of MG by BC-WP (94.25%) was attained under a solution pH of 10, a BC concentration of 12 g/L, and an average BC particle size of 225 μm. Furthermore, the validated regression model was found to explain 94.72% of the obtained results, demonstrating the ability of BC-WP to remove the target dye. Thus, a new and sustainable alternative to conventional systems for treating dye-polluted water is proposed, utilizing the solid by-product of the thermochemical process, contributing to the circular economy.