A parametric optimization for leveraging the potential of ammonia modified magnetic pine cone hydrochar for Cr (VI) contaminated wastewater treatment

The present study evaluated the biosorption potential of magnetic pine cone hydrochar (MPHC) for chromium removal from wastewater. Initially, three different methodologies were followed for the synthesizing magnetic hydrochar and were tested for chromium removal and with a maximum removal of 91.3%, ammonia-modified MPHC showed its tremendous potential for Cr (VI) removal. Further, the hydrochar was characterized physically, chemically, magnetic, and morphological and a Box-Behnken experimental design was used for examining the effect of all the five parameters for Cr (VI) removal from the simulated wastewater system. Ammonia-modified MPHC showed a removal efficiency of 98.46% under the optimized batch shake flask system with the initial chromium concentration (55 mg/L), MPHC dose (550 mg/L), temperature (40 °C) and reaction time (120 min) and iron-MPHC ratio (30%). Here, the maximum Cr (VI) adsorption capability (q_e) was found to be 154 mg/g. Further, the effect of different bed height, inlet pollutant flow rate, and inlet pollutant concentration during the continuous packed bed biosorption study showed a significant removal. The breakthrough curves for Cr (VI) removal obtained via the continuous flow-through column study confirmed that MPHC in the fixed-bed column suits Cr (VI) removal.