Magnetite-impregnated biochar of parthenium hysterophorus for adsorption of Cr(VI) from tannery industrial wastewater

Abstract The tannery industry inevitably generates toxic and catastrophic wastewater, which results in a huge threat to public health and water resources. Therefore, this work aimed to synthesize parthenium hysterophorus-based biochar–Fe 3 O 4 composite for removal of Cr(VI) from tannery wastewater under 3 4 full factorial experimental designs of the Box–Behnken, which was analyzed using response surface methodology under four independent factors of pH (3, 6, and 9), initial Cr(VI) concentrations (40, 70, and 100 mg/L), contact times (30, 60, and 90 min), and adsorbent doses (20, 60, and 100 mg/100 mL). This composite adsorbent was described by a high BET surface area of 237.4 m 2 /g, XRD prominent peaks, SEM morphology corroborate and FTIR multifunctionalities of O–H at 3296 cm −1 , the vibration of ketone C–OH at 1240 cm −1 , and the vibration of C–O–C at 1147 cm −1 and Fe–O stretching at 542 cm −1 . The maximum Cr(IV) removal efficiency of 91.8% was recorded at an initial Cr(VI) concentration of 40 mg/L, pH of 3, adsorbent dose of 100 mg/100 mL, and a contact time of 90 min, whereas the minimum Cr(VI) removal of 17.3% was observed at an initial Cr(VI) concentration of 100 mg/L, 20 mg/100 mL of adsorbent dose, pH of 9, and contact time of 30 min. The concentration of Cr(VI) in real wastewater was determined to be 85.13 mg/L and its remediation was found to be 81.8%. Langmuir’s model was the best fit with experimental data at R 2 0.99 and q max 400 mg/g, showing that the adsorption process was homogenous and monolayer. In conclusion, the adsorption results were encouraging, and biochar–Fe 3 O 4 appears to be a potential candidate for Cr removal from wastewater.