Use of Pine cone as bio-coagulant for heavy metal removal from industrial wastewater: Use of Box–Behnken design

This study investigated the potential of Pine cones (Pinus nigra) as a natural bio-coagulant for removing heavy metals such as iron, zinc, and copper from industrial wastewater. Pine cones powder (PCP) was characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to identify potential components active in bio-coagulation. Active components were extracted from Pine cones using distilled water and identified as proteins, total sugars, and total phenols. Two steps were employed for process optimization: jar test experiments for preliminary evaluation to identify the factors influencing coagulation activity, followed by response surface methodology (RSM) using Box–Behnken Design (BBD) to examine the effects of each factor and their interaction. The study's variables were coagulant dosage (X1), pH (X2), and settling time (X3), while the responses were iron removal (Y1), zinc removal (Y2), and copper removal (Y3). The optimal conditions for iron removal were found to be 50 mL/L coagulant dosage, pH 10, and 30 min settling time, achieving a removal efficiency of 99.81%. Zinc and copper removal required longer settling times (120 min) and achieved efficiencies of 98.82% and 90.58%, respectively. Analysis of variance (ANOVA) confirmed the adequacy of the quadratic regression models. The determination coefficients (R²) were notably high at 98.76%, 99.61%, and 97.58% for iron, zinc, and copper removal, respectively. p-values for all metals were below 0.05, with F-values of 44.32, 143.39, and 22.43 for iron, zinc, and copper removal, respectively, confirming model adequacy. This study demonstrates the effectiveness of Pine cones as a natural coagulant for removing heavy metals from wastewater. The optimized conditions using BBD provide a promising and sustainable approach to wastewater treatment.