Anion Effect on Cu²⁺ Adsorption on NH₂-MCM-41

Abstract

The anion effect was investigated for the copper adsorption on NH2-MCM-41 from Cu(NO3)2 and CuSO4 solutions. The copper adsorption was higher and faster in the presence of SO4 2− anion compared to NO3 −. The MCM-41 possesses well-ordered mesopores that are readily accessible and a uniform surface that is amenable to the attachment of the chemical moieties for creating tailored adsorption sites. The adsorption sites on NH2-MCM-41 were created by grafting aminopropyls on MCM-41, and the random deposition resulted in a site distribution best described by the Freundlich equation. The majority of the adsorption sites (i.e., up to 70%) are readily accessible to Cu2+ adsorption. The remaining sites were only accessible in the presence of SO4 2−. Evidence showed that the SO4 2− anion affects the adsorption by interacting with the dissolved copper to form [CuSO4]0 species, coadsorbing with Cu2+ to form stable complexes, and may even indirectly react with the weakly acidic silanol groups to liberate aminopropyls for more Cu2+ adsorption.

Effects of inorganic electrolyte anions on enrichment of Cu(II) ions with aminated Fe3O4/graphene oxide: Cu(II) speciation prediction and surface charge measurement

“…Besides, the amino groups on AMGO surface might interact with the hydroxyl group by hydrogen bond. The SO 4 2À in solution could liberate these amino groups for more Cu 2+ adsorption and further participate by forming a stable complex with the adsorbed Cu 2+ (Lam et al, 2008). The effect of CO 3 2À on the adsorption of Cu(II) onto AMGO composite is shown in Fig.…”

“…Lam et al (2008) indicated that the Cu 2+ adsorption required at least two sites and could not adsorb on the isolated sites. The SO 4 2À stabilized the Cu 2+ adsorption on the individual amino sites, that is, the SO 4 2À could act as one of the adsorption sites, therefore improving the adsorption capacity for Cu(II) ions (Lam et al, 2008). Besides, the amino groups on AMGO surface might interact with the hydroxyl group by hydrogen bond.…”

“…From Fig. 3f reasons for the increase of Cu(II) removal in the presence of Na 2 HPO 4 : (1) the decrease in zeta potential of AMGO surface due to the adsorption of negative HPO 4 2À made the positively charged Cu(II) ions much easier to be captured by adsorption sites (Sheng et al, 2014); (2) the Cu(II) ions could be captured by the adsorbed HPO 4 2À and then formed a ternary cation-anion-surface complex (Collins et al, 1999); (3) the HPO 4 2À could enhance the Cu(II) adsorption by stabilizing the Cu 2+ adsorption on the unfavorable sites and by anchoring CuHPO 4 complex on the isolated amino sites (Lam et al, 2008); (4) the metal-ligand complex could precipitate from solution, thereby resulting in the increase of the Cu(II) removal.…”

“…Adsorption is a popular and economical method for treating metal pollutions in natural water and wastewater (Babel and Kurniawan, 2003;Lam et al, 2008). Many studies have shown that heavy metals could be efficiently adsorbed by a wide variety of adsorbents (Babel and Kurniawan, 2003;Lam et al, 2008;Bui and Choi, 2010;Liu et al, 2011;Hu et al, 2013).…”

“…Many studies have shown that heavy metals could be efficiently adsorbed by a wide variety of adsorbents (Babel and Kurniawan, 2003;Lam et al, 2008;Bui and Choi, 2010;Liu et al, 2011;Hu et al, 2013). Graphene oxide (GO) is an ideal material for removing heavy metals from aqueous solution due to its exceptional physicochemical properties.…”