Abstract: This study aims to optimize the use of lacquer residue biomass (LBM). We investigated the ability of LBM to remove Pb²⁺ heavy metal ions and the typical cationic dye methylene blue (MB) and anionic dye Congo red (CR) by simultaneous adsorption from composite systems, as well as the relevant factors. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize adsorption behavior. The adsorption kinetics of Pb²⁺-MB/CR composite systems can be effectively characterized by the pseudo-second-order kinetic model (R²>0.97). In the Pb²⁺-MB composite system, adsorption was antagonistic with similar adsorption sites. However, in the Pb²⁺-CR composite system, we found that adsorption was synergistic with different adsorption sites, which led to a higher simultaneous adsorption capacity for a higher initial Pb²⁺-CR concentration, unlike the Pb²⁺-MB system. In both composite systems, an appropriate increase in LBM dosage and system temperature within a certain range was conducive to simultaneous adsorption and removal of Pb²⁺-MB/CR composite systems. The optimal solid–liquid ratio and temperature were 1∶‍75 and 30°C, respectively. The adsorption and removal rates of Pb²⁺ and MB were 99.98% and 90.49%, respectively, and those of Pb²⁺ and CR were 93.99% and 77.39%, respectively, in (50, 50) mg/L of Pb²⁺-MB/CR composite systems under these conditions. Adsorption removal of Pb²⁺ and MB improved with higher pH levels, and worsened with the increase of ionic strength in the solution, while the removal rate of CR showed an opposite trend. The coexisting anion and cation types had limited influence on the simultaneous adsorption removal of Pb²⁺, MB, and CR. The results of desorption showed that LBM can be utilized as a disposable material for simultaneously treating Pb²⁺-MB/CR composite systems. The simultaneous adsorption mechanisms of Pb²⁺-MB/CR mainly involved hydrogen bonding, π–π bonding interaction, and electrostatic interaction.

Key words: Lacquer residue biomass (LBM); Lead; Methylene blue (MB); Congo red (CR); Simultaneous adsorption removal

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