The Influence of Salt Anions on Heavy Metal Ion Adsorption on the Example of Nickel

Abstract

The biodegradable polysaccharide chitosan possesses protonated and natural amino groups at medium pH values and has therefore been used as an adsorbing material for nickel salts in water treatment. Nickel is a problematic heavy metal ion which can cause various diseases and disorders in living organisms. Here, we show the influence of oxyanions (e.g., nitrate and sulfate) to the adsorption of nickel ions. Hence, simultaneously we are addressing the increasing global problem of nitrate and sulfate ion pollution in groundwater and surface water. A series of adsorption experiments was carried out in order to determine (i) the adsorption equilibrium, (ii) the adsorption capacity in dependence on the initial nickel ion concentration, and (iii) the influence of the anion presented in solution for the adsorption capacity. Surface morphology of chitosan flakes before and after the adsorption process has been studied with SEM-EDX analysis. The chitosan flakes exhibited promising adsorption capacities of 81.9 mg·g−1 and 21.2 mg·g−1 for nickel (sulfate) and nickel (nitrate), respectively. The calculated values of Gibbs free energy change ΔG0 confirm the higher adsorption of nickel ions in presence of sulfate ions. Hence, higher anion valence leads to a higher adsorption capacity.

Solubility and Selectivity Effects of the Anion on the Adsorption of Different Heavy Metal Ions onto Chitosan

“…Thus, for every investigated heavy metal ion the adsorption capacity is highly dependent on the corresponding anion of the metal salt. As previously described, chitosan features the ability to adsorb simultaneously heavy metal ions and oxyanion like sulfate [31,32]. This observation is valid for most heavy metal salts.…”

“…Previously, we studied the adsorption of CuSO 4 , FeSO 4 , and NiSO 4 on chitosan and could show that besides the known adsorption of the heavy metal ion, the sulfate ions adsorb as well [31]. Subsequently, we used NiSO 4 and Ni(NO 3 ) 2 to understand the influence of the oxyanion for the adsorption of heavy metal ions on chitosan on the example of nickel salts [32]. The adsorption isotherms showed huge differences in the adsorption capacities for nickel in dependence of the corresponding anion.…”

Removal and Separation of Heavy Metal Ions from Multicomponent Simulated Waters Using Silica/Polyethyleneimine Composite Microparticles

“…Therefore, surface water treatment requires materials in which hardness and accessibility can be combined with flexibility and high number of active FGs in one “entity” with upgraded properties (high sorption capacity, fast kinetics, high selectivity, fast regeneration, and good reusability). These materials could be composite sorbents which fulfill the utility in fast targeting of different types of pollutants, such as heavy metal ions. − The control of FGs at a nanometric level and the creation of specific ligands onto composites (magnetic particles, membranes, carbon nanosheets, and hydrogels) for subsequent molecular interactions is essential in water purification, chromatography, controlled release of immobilized species, and so forth. − For some materials, high amounts of sorbed metal was reached at high equilibrium concentration in hundreds of minutes, in case of hydrogels and ionic resins where diffusion is a very important parameter of sorption. ,,, Other authors succeeded in decreasing the time of sorption by increasing the surface of the sorbent, in case of magnetic nanoparticles. , The inorganic/polyelectrolyte composites, with controlled architecture and chemical composition at nanometric level, can be obtained by: (i) polymerization of a monomer/colloidal particles mixture, (ii) polymer chains grafting onto/from solid surface, and (iii) deposition of thin films using monolayer or layer-by-layer (LbL) strategy. − LbL assembly, carried out mainly in aqueous environments, is an extensively used technique for engineering material surfaces and fabrication of LbL composite coatings. , The mechano-chemical stability of the composite multilayer under harsh/stress media is very important in sorption/separation of different pollutants (heavy metal ions, dyes, drugs, humic acids, etc.). Thus, thermal/chemical cross-linking of polymer chains on a composite surface must be carried out, either at the end or at each step of the LbL process .…”

Mineral Materials Coated with and Consisting of MnOx—Characteristics and Application of Filter Media for Groundwater Treatment: A Review

“…The question is more complex, because of the possible occurrence of some adsorption reactions without the release of proton, irrespective of ionic strength and the nature of electrolyte solution, which suggests the metal adsorbs on MnO x with high surface charge not only as free ions, but also as some of its complexes [140]. In addition, the removal efficiency of metals is intensified because of precipitation of hydroxides at higher concentration of component and at higher pH [40] as well as because of higher co-anion valence leads to a higher adsorption capacity [141].…”