Abstract
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•Different background electrolytes had different effects on the Cd(II) removal.•Visual MINTEQ could be applied to the chemical speciation calculations.•The influence of Na3PO4 on the Cd(II) adsorption was complicated.•The adsorption process could be well described by the Freundlich isotherm model.•Adsorption isotherms were affected by background electrolytes and ionic strength.
To elucidate the influence mechanisms of background electrolytes and ionic strength on Cd(II) removal, the adsorption of Cd(II) onto magnetic graphene oxide–supported sulfanilic acid (MGO–SA) in aqueous solutions containing different types and concentrations of background electrolytes was studied. The results indicate that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The Cd(II) removal was decreased with the presence of background electrolyte cations (Na+, K+, Ca2+, Mg2+, Mn2+, Zn2+, and Ni2+), and the divalent cations exerted more obvious influences on the Cd(II) uptake than the monovalent cations at pH 6. Both Cl− and NO3− had negative effects on Cd(II) adsorption because they can form water-soluble metal–anion complexes with Cd(II) ions. The presence of 0.01molL−1 Na3PO4 reduced the removal percentage of Cd(II) at pH<5 but extremely enhanced the Cd(II) removal when the pH>5. The Cd(II) adsorption was sensitive to changes in the concentration of NaCl, NaNO3, NaClO4, and Na3PO4. Besides, the adsorption isotherm of Cd(II) onto MGO–SA could be well described by the Freundlich model and was also influenced by the type of background electrolyte ions and the ionic strength.