Nanoscale zero-valent iron (nZVI) loaded on tea residue biochar activated with phosphoric acid composites was synthesized. This adsorbent can efficiently adsorb multiple heavy metal ions such as Pb (II), Cr (III), Cu (II), and Ni (II) simultaneously. The adsorption process was found to follow the pseudo-second-order kinetic model. Equilibrium adsorption capacities reached 288.18, 162.34, 242.72, and 267.22 mg·g⁻¹ for Pb(II), Cr(III), Cu(II), and Ni(II), respectively. The common interfering ions exhibited lower influence on its adsorption capacity. The adsorption mechanism includes reduction, ion exchange, surface complexation and precipitation. Furthermore, the waste adsorbent was converted into a catalyst in situ, which could catalyze the degradation of Congo red by establishing an electron transfer pathway. This research provides a new concept for the sustainable utilization of industrial tea residues and the harmless treatment of waste nZVI composite adsorbents.

中文翻译：

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负载纳米零价铁的茶渣生物炭高效吸附多种重金属

合成了负载在磷酸复合物活化的茶渣生物炭上的纳米级零价铁（nZVI）。该吸附剂可同时高效吸附Pb(II)、Cr(III)、Cu(II)、Ni(II)等多种重金属离子。发现吸附过程遵循准二级动力学模型。平衡吸附容量分别达到288.18、162.34、242.72和267.22 mg·g ^-1分别为 Pb(II)、Cr(III)、Cu(II) 和 Ni(II)。常见的干扰离子对其吸附能力的影响较小。吸附机理包括还原、离子交换、表面络合和沉淀。此外，废物吸附剂被原位转化为催化剂，可以通过建立电子转移途径催化刚果红的降解。该研究为工业茶渣的可持续利用和废弃nZVI复合吸附剂的无害化处理提供了新的思路。