The valorization of agricultural waste as biosorbent requires studies dealing with aqueous systems containing coexisting heavy metals. Batch adsorption experiments were carried out to study the competitive biosorption of Ni(II) and Cd(II) on alkali-modified lemon peel. The biosorption kinetic analysis indicated that the uptake of Ni(II) on lemon peel was better described by pseudo first-order model whereas for Cd(II) results were no conclusive. A rapid uptake of both metals on alkali-modified lemon peel was detected during the first 10 min obtaining more than 90% of the maximum sorption. The maximum adsorption capacity of Ni(II) and Cd(II) for single metal systems at optimum conditions (pH = 5, S/L = 5 g L${}^{-1}$, 25 ${}^{\underline{\circ }}\mathrm{C}$), which were obtained from Langmuir model, reached as high as about 0.626 and 0.726 mmol g${}^{-1}$, respectively. These values were reduced 30 and 20 % in the presence of 100 mg L${}^{-1}$ of Cd and Ni, respectively. Regarding the reusability of the biosorbent, after five consecutives adsorption–desorption cycles using HNO₃ and H${}_2$SO₄ as desorption reagents percentages of 90 and 70 % were recovered for Ni and Cd. The promising results obtained through this work are expected to promote the use of lemon peel as an efficient biosorbent for industrial applications.

农业废弃物作为生物吸附剂的价值评估需要研究含有重金属共存的水性体系。进行了批量吸附实验，以研究Ni（II）和Cd（II）在碱改性柠檬皮上的竞争性生物吸附。生物吸附动力学分析表明，通过伪一级模型可以更好地描述柠檬皮上Ni（II）的吸收，而Cd（II）的结果尚无定论。在最初的10分钟内，检测到两种金属在碱改性柠檬皮上的快速吸收，获得了最大吸附量的90％以上。在最佳条件下（pH = 5，S / L = 5 g L ），单金属系统对Ni（II）和Cd（II）的最大吸附容量${}^{-\mathrm{1个}}$，25 ${}^{\underline{\circ }}\mathrm{C}$从Langmuir模型获得的）分别高达0.626和0.726 mmol g${}^{-\mathrm{1个}}$， 分别。在100 mg L存在下，这些值降低了30％和20％${}^{-\mathrm{1个}}$分别为Cd和Ni。关于生物吸附剂的可重复使用性，使用HNO ₃和H连续五个连续的吸附-解吸循环后${}_2$Ni和Cd的SO ₄作为脱附试剂的百分比分别为90％和70％。通过这项工作获得的有希望的结果有望促进柠檬皮作为工业应用的有效生物吸附剂的使用。