Cadmium, mercury, and nickel adsorption by tetravalent manganese feroxyhyte: selectivity, kinetic modeling, and thermodynamic study.

Title Cadmium, mercury, and nickel adsorption by tetravalent manganese feroxyhyte: selectivity, kinetic modeling, and thermodynamic study.
Authors E. Kokkinos; K. Soukakos; M. Kostoglou; M. Mitrakas
Journal Environ Sci Pollut Res Int
DOI 10.1007/s11356-017-9738-2
Abstract

This study is aiming to investigate tetravalent manganese feroxyhyte (TMFx) adsorption efficiency in removing heavy metals. The motivation of this study was the fact that TMFx is a highly negatively charged nanostructure material and that the metals Cd, Hg, and Ni were characterized as priority pollutants for drinking water. TMFx was evaluated through batch and continuous flow experiments in National Sanitation Foundation (NSF) water matrix which simulated the physicochemical characteristics of natural water. Water's pH significantly influences Cd and Ni adsorption efficiency which gradually increases when pH value rises from 5 to 9, while the corresponding one for Hg remains almost constant. Thermodynamic data showed a spontaneous and an exothermic nature weak-chemisorption (??° = -17.5 ± 2 kJ/mol) of Cd, Ni, and Hg by TMFx. The determined ranking of adsorption affinity and selectivity (Cd > Ni > Hg) seems to be governed by the metals' speciation, as well as by hydration free energy, which is influenced, however, by their atomic radius. The lower adsorption capacity and selectivity of TMFx for Hg should be attributed both to uncharged species and to higher atomic radius. The similar Cd and Ni speciation in the NSF water matrix leads to the conclusion that the better affinity, selectivity, and adsorption kinetic of Cd versus Ni should be attributed to the lower hydration free energy of Cd which is in turn related to its higher atomic radius. The faster adsorption kinetic (Hg > Cd > Ni) of Hg may be attributed to the lower radius of its anhydrate species. Furthermore, TMFx showed high removal efficiency under continuous flow application in an adsorption bed setup. The determined uptake capacity (q RL) at equilibrium-breakthrough concentration equal to the drinking water regulation limit (RL) of each metal were q 1 = 2.5 ?g Hg/mg TMFx, q 5 = 5.2 ?g Cd/mg TMFx, and q 20 = 7.1 ?g Ni/mg TMFx. Leaching tests of spent TMFx samples from the rapid small-scale column tests (RSSCTs) could be treated either as inert wastes after Cd and Ni adsorption or as non-hazardous waste after Hg adsorption.

Citation E. Kokkinos; K. Soukakos; M. Kostoglou; M. Mitrakas.Cadmium, mercury, and nickel adsorption by tetravalent manganese feroxyhyte: selectivity, kinetic modeling, and thermodynamic study.. Environ Sci Pollut Res Int. 2017. doi:10.1007/s11356-017-9738-2

Related Elements

Cadmium

See more Cadmium products. Cadmium (atomic symbol: Cd, atomic number: 48) is a Block D, Group 12, Period 5 element with an atomic weight of 112.411. Cadmium Bohr ModelThe number of electrons in each of Cadmium's shells is 2, 8, 18, 18, 2 and its electron configuration is [Kr]4d10 5s2. The cadmium atom has a radius of 151 pm and a Van der Waals radius of 230 pm. Cadmium was discovered and first isolated by Karl Samuel Leberecht Hermann and Friedrich Stromeyer in 1817. In its elemental form, cadmium has a silvery bluish gray metallic appearance. Cadmium makes up about 0.1 ppm of the earth's crust. Elemental CadmiumNo significant deposits of cadmium containing ores are known, however, it is sometimes found in its metallic form. It is a common impurity in zinc ores and is isolated during the production of zinc. Cadmium is a key component in battery production and particular pigments and coatings due to its distinct yellow color. Cadmium oxide is used in phosphors for television picture tubes. The name Cadmium originates from the Latin word 'cadmia' and the Greek word 'kadmeia'.

Manganese

See more Manganese products. Manganese (atomic symbol: Mn, atomic number: 25) is a Block D, Group 7, Period 4 element with an atomic weight of 54.938045. Manganese Bohr ModelThe number of electrons in each of Manganese's shells is [2, 8, 13, 2] and its electron configuration is [Ar] 3d5 4s2. The manganese atom has a radius of 127 pm and a Van der Waals radius of 197 pm. Manganese was first discovered by Torbern Olof Bergman in 1770 and first isolated by Johann Gottlieb Gahn in 1774. In its elemental form, manganese has a silvery metallic appearance. Elemental ManganeseIt is a paramagnetic metal that oxidizes easily in addition to being very hard and brittle. Manganese is found as a free element in nature and also in the minerals pyrolusite, braunite, psilomelane, and rhodochrosite. The name Manganese originates from the Latin word mangnes, meaning "magnet."

Mercury

Mercury Bohr ModelSee more Mercury products. Mercury (atomic symbol: Hg, atomic number: 80) is a Block D, Group 12, Period 6 element with an atomic weight of 200.59. The number of electrons in each of mercury's shells is 2, 8, 18,32, 18, 2 and its electron configuration is [Xe] 4f14 5d10 6s2. The mercury atom has a radius of 151 pm and a Van der Waals radius of 209 pm. It is named after the planet Mercury and often referred to as "quicksilver" due to its appearance as a silvery liquid. Mercury has low melting and boiling points. It is a poor conductor of heat, but a fair conductor of electricity. Mercury is found both as a free element and in cinnabar, corderoite, and livingstonite ores.

Nickel

See more Nickel products. Nickel (atomic symbol: Ni, atomic number: 28) is a Block D, Group 4, Period 4 element with an atomic weight of 58.6934. Nickel Bohr ModelThe number of electrons in each of nickel's shells is [2, 8, 16, 2] and its electron configuration is [Ar]3d8 4s2. Nickel was first discovered by Alex Constedt in 1751. The nickel atom has a radius of 124 pm and a Van der Waals radius of 184 pm. In its elemental form, nickel has a lustrous metallic silver appearance. Nickel is a hard and ductile transition metal that is considered corrosion-resistant because of its slow rate of oxidation. Elemental NickelIt is one of four elements that are ferromagnetic and is used in the production of various type of magnets for commercial use. Nickel is sometimes found free in nature but is more commonly found in ores. The bulk of mined nickel comes from laterite and magmatic sulfide ores. The name originates from the German word kupfernickel, which means "false copper" from the illusory copper color of the ore.