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This study investigates the P and NO₃⁻ adsorption capacities of different biochars made from plant waste including rice straw (RSB), <i>Phragmites communis</i> (PCB), sawdust (SDB), and egg shell (ESB) exposed to a range of pyrolysis temperatures (300, 500 and 700 °C). Results indicate that the effect of pyrolysis temperature on the physiochemical properties of biochar varied with feedstock material. Biochars derived from plant waste had limited adsorption or even released P and NO₃⁻, but adsorption of P capacity could be improved by adjusting pyrolysis temperature. The maximum adsorption of P on RSB700, PCB300, and SDB300, produced at pyrolysis temperature of 700, 300 and 300 °C, was 5.41, 7.75 and 3.86 mg g⁻¹, respectively. ESB can absorb both P and NO₃⁻, and its adsorption capacity increased with an increase in pyrolysis temperature. The maximum NO₃⁻ and P adsorption for ESB700 was 1.43 and 6.08 mg g⁻¹, respectively. The less negative charge and higher surface area of ESB enabled higher NO₃⁻ and P adsorption capacity. The P adsorption process on RSB, PCB, SDB and ESB, and the NO₃⁻ adsorption process on ESB were endothermic reactions. However, the NO₃⁻ adsorption process on RSB, PCB and SDB was exothermic. The study demonstrates that the use of egg shell biochar may be an effective way to remove, through adsorption, P and NO₃⁻ from wastewater.