Synchronous removal of ammonium and phosphate from swine wastewater by two agricultural waste based adsorbents: Performance and mechanisms

[Display omitted] •Two agro–wastes were used to remove ammonium and phosphate.•Their high adsorption performance from swine wastewater was achieved.•Ammonium and phosphate removals were positively correlated with the pH value.•Surface negative charge, O–H, Ca2+ and Mg2+ worked in removal processes. Two agricultural wastes, Chinese medicinal herbal residue and spent Pleurotus ostreatus substrate, were developed to remove ammonium and phosphate from swine wastewater. These adsorbents were mesoporous materials with abundant smooth layered pores, and rough protuberances and grooves, respectively. Their adsorption capacities were 1131.65 and 1631.79 mg N g−1, and 63.41 and 62.58 mg P g−1 at pH 8.0, dosage of 0.2 g L−1 and contact time of 360 min. And kinetics data of ammonium and phosphate fitted best with the intra–particle diffusion and pseudo–second–order models, respectively. Based on the point of zero charge, FTIR and XPS analyses, ammonium was removed mainly by electrostatic attraction, ion exchange and surface precipitation, while phosphate was by ligand exchange, surface complexation and precipitation. Therefore, the two agricultural wastes have great potential to synchronously remove ammonium and phosphate from swine wastewater.