Simultaneous adsorption of tetracycline, ammonium and phosphate from wastewater by iron and nitrogen modified biochar: Kinetics, isotherm, thermodynamic and mechanism

The simultaneous removal of various pollutants in wastewater is increasingly deserved attention. In this study, an efficient adsorbent Fe/N@BC was synthesized by Fe-N co-modification. The adsorbability of Fe/N@BC was evaluated using a mixture with tetracycline (TC), NH4+-N and PO43-P. In comparison to BC, N@BC and Fe@BC, Fe/N@BC exhibited an excellent performance for simultaneously absorbing TC, NH4+-N and PO43-P. The pseudo-first-order was used to describe the adsorption process of NH4+-N and PO43-P, while the pseudo-second order could be well fitted to TC adsorption data. The adsorption isotherms of TC, NH4+-N and PO43-P were more in line with Sips model (Adj.R-2 > 0.97). The maximum adsorption capacities of Fe/N@BC towards TC, NH4+-N and PO43-P were 238.94, 111.87 and 165.02 mg g(-1), respectively, which were 1.31-1.91 times than that of BC, N@BC and Fe@BC. The simultaneous adsorption mechanism mainly involved pore filling, electrostatic interaction, ion exchange, surface complexation, surface precipitation, H bond and pi-pi interaction. Furthermore, after six cycles, the removal efficiencies of TC, NH4+-N and PO43-P were 75.3, 66.1 and 64.5% by Fe/N@BC, highlighting its promising potential to adsorb multi-pollutants from aqueous solution.

Automated summary

In this study, an efficient adsorbent Fe/N@BC was synthesized by Fe-N co-modification for the simultaneous removal of tetracycline, NH4+-N and PO43-P from wastewater. Fe/N@BC exhibited excellent adsorption performance and higher adsorption capacities compared to other adsorbents. The adsorption mechanism involved various interactions such as pore filling, electrostatic interaction, ion exchange, surface complexation, surface precipitation, H bond and pi-pi interaction. Fe/N@BC also showed promising potential for multi-pollutant removal even after multiple cycles.