Facile preparation of magnetic nano-Fe3O4 modified powdered coconut shell biochar for COD deep removal in oil field produced water

The oilfield produced water (PW) treated by traditional process difficult to reduce the chemical oxygen demand COD value to below 50 mg/L. In this work, magnetic nano-Fe 3 O 4 modified powdered coconut shell biochar was successfully prepared. The COD value of the PW was reduced from an initial value of 387 mg/L to 37 mg/L in 10 min of low speed mixing using magnetic nano-Fe 3 O 4 modified powdered coconut shell biochar. In addition, the spent magnetic nano-Fe 3 O 4 modified powdered coconut shell biochar can be regenerated by heating at 240 °C for 20 min. The regenerated magnetic nano-Fe 3 O 4 modified powdered coconut shell biochar showed excellent adsorption properties, and the COD value of the PW was reduced to about 35 mg/L in all six recycles.