Parametric Study of COD Reduction from Textile Processing Wastewater Using Adsorption on Cypress Cone-Based Activated Carbon: An Analysis of a Doehlert Response Surface Design

In this study, the performance of a cypress cone-based activated carbon was tested for the COD reduction from industrial textile wastewater. These cypress cones were locally collected after maturation. The Doehlert response surface design was used to simulate and optimize the decrease in COD in treated wastewater. The dominant parameters for COD removal in the effluent were the temperature, the amount of adsorbent and the pH of the initial solution. The obtained model fit the experimental results with high precision (R² > 0.93) and low Fisher probability (< 0.0001), which reflected a strong statistical significance. Additionally, the model shows the order of parameters importance as follows: adsorbent amount > temperature > initial pH. Under the optimal conditions predicted by the regression, a maximum COD reduction could be obtained with a temperature of 319 K at pH 12 and an activated carbon concentration of 1.144 g L⁻¹ after 1 h treatment. Meanwhile, the designed adsorbent realized the decrease in colour (80.4%), COD (19%) and turbidity (67.1%) of wastewater. It could be concluded that cypress cone-based activated carbon is promising in the treatment of textile wastewater. The increase in COD removal rate through hybridization of processes is being considered for future research.