Simultaneous adsorption of heavy metals in complex multi metal system is insufficiently explored. This research gives results of key process parameters optimization for simultaneous removal of Cd(II), Co(II), Cr(III), Cu(II), Mn(II), Ni(II) and Pb(II) from aqueous solution (batch system). New lemon peel-based biomaterial was prepared and characterized by infrared spectroscopy with Fourier transformation (FTIR), scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), while the quantification of metals was made by atomic absorption spectrometry (AAS). Simultaneous removal of seven metals ions was favorable at pH 5 with 300 mg/50 mL solid-liquid phase ratio, within 60 min at room temperature with total obtained adsorption capacity of 46.77 mg g⁻¹. Kinetic modeling showed that pseudo-second order kinetic and Weber-Morris diffusion models best describe the adsorption mechanism of all seven heavy metals onto lemon peel.

A procedure for the determination of trace levels of Cd, Co, Cr, Fe, Mn, Ni, and Pb by flame atomic absorption spectrometry using a column preconcentration system is described in which the metals were adsorbed on pulverized banana peel, an economically and environmentally acceptable sorbent. In the optimization procedure, five variables (sample pH, mass of biosorbent, type of eluent, sample flow rate, and volume) were optimized and the capacity of the biosorbent was established. Under the optimized conditions, the detection limits of the method were 2.4, 27.0, 49.4, 31.1, 6.7, 29.6, and 46.2 µg L⁻¹ for Cd, Co, Cr, Fe, Mn, Ni, and Pb, respectively. The precision, expressed as relative standard deviation, was less than 4% based on twelve measurements. The recoveries were 81.1% (Cd), 91.4% (Co), 87.2% (Cr), 90.1% (Fe), 88.0% (Mn), 94.1% (Ni), and 93.2% (Pb) under the optimum conditions (pH; 9, sample flow rate; 3 mL min⁻¹, mass of biosorbent; 200 mg; eluent; 1 mol L⁻¹ nitric acid, preconcentration factor; 10). The sorption capacity of pulverized banana peel was 15.12, 28.85, 32.70, 30.44, 30.94, 28.97, and 8.21 µmol per gram of adsorbent for Cd, Co, Cr, Fe, Mn, Ni, and Pb, respectively.