Moss biomass as effective biosorbents for heavy metals in contaminated water

Abstract

The study explored batch adsorption of Cd(II) and Pb(II) ions using moss biomass from Barbula consanguinea and Hyophila involuta, assessing removal efficiency concerning various parameters. Both moss species showed high removal rates for Cd(II) (87 % for B. consanguinea and 89 % for H. involuta) and Pb(II) (93 % for B. consanguinea and 94 % for H. involuta) from contaminated water, reaching equilibrium within 30 min. While Cd(II) removal was pH-independent, Pb(II) removal showed pH-dependence, peaking at pH 5.0–5.5. Adsorption isotherm analysis indicated that the Langmuir, Freundlich, Elovich, Sips, and Redlich-Peterson models best described Cd(II) and Pb(II) adsorption onto both moss species (except for Cd(II) adsorption onto H. involuta), with R2 > 0.98. This confirms a heterogeneous surface with both monolayer and multilayer adsorption sites. The pseudo-second-order kinetic model confirmed chemisorption on moss biomass from both species. FTIR spectra identified major binding sites such as phenols, alkaloids, amines, alkenes, nitro compounds, and low-molecular-weight carbohydrates. EDS analysis validated the bonding of Cd(II) and Pb(II) ions to the biomass surface by displacing Ca(II) ions. According to the Langmuir model, moss biomass exhibited selective adsorption, favoring Pb(II) over Cd(II). B. consanguinea showed a higher adsorption capacity than H. involuta, which is attributed to its higher negative zeta potential. This study underscores the novelty of moss biomass for heavy metal removal in wastewater treatment, highlighting its sustainability, effectiveness, cost-efficiency, versatility, and eco-friendliness.