Competitive adsorption of metals on cabbage waste from multi-metal solutions

• Modified Langmuir model described well the multi-metal adsorption system.
• Adsorbent from cabbage waste is effective for Pb(II) and Cd(II) adsorption.
• High interference among the metals was observed in a multi-metal system.
• Adsorption capacity was suppressed by the presence of other metal ions.
• The highest reduced in adsorption capacities were found for Pb(II), Zn(II) and Cd(II).

This study assessed the adsorption capacity of the agro-waste ‘cabbage’ as a biosorbent in single, binary, ternary and quaternary sorption systems with Cu(II), Pb(II), Zn(II) and Cd(II) ions. Dried and ground powder of cabbage waste (CW) was used for the sorption of metals ions. Carboxylic, hydroxyl, and amine groups in cabbage waste were found to be the key functional groups for metal sorption. The adsorption isotherms obtained could be well fitted to both the mono- and multi-metal models. In the competitive adsorption systems, cabbage waste adsorbed larger amount of Pb(II) than the other three metals. However, the presence of the competing ions suppressed the sorption of the target metal ions. Except the case of binary system of Cd(II)–Zn(II) and Cd(II)–Cu(II), there was a linear inverse dependency between the sorption capacities and number of different types of competitive metal ions.