Abstract
Chelating and ion-exchange N-functionalized mesoporous silicas (SBA-15) as selective adsorbents for removal of heavy metals were synthesized using template method. Fourier transform infrared spectroscopy, TEM analysis, N2 adsorption/desorption isotherms and titration analysis confirmed successful functionalisation of the tri-sodium salt of N-(triethoxysilylpropyl)ethylenediaminetriacetic acid (EDTA), protonated primary amine (NH3+Cl−) and its combinations onto the mesoporous silica (SBA-EDTA/NH2). The obtained materials featured beneficial properties of mesoporous silica SBA-15 with its high surface area and were successfully fictionalized with N-containing groups. The synthesized series of silicas were investigated for removal of Cr(III), Mn(III), Pb(II), Cd(II) and Cu(II) from model water solutions. The adsorption of target ions increased with the increase pH and its concentration in solution. The adsorption equilibrium data were well fitted to Langmuir isotherm model and maximum monolayer adsorption capacities for cations Pb(II), Cd(II), Cr(III) and Mn(II) were 185.6 mg g−1, 111.2 mg g−1, 57.7 mg g−1 and 49.4 mg g−1, respectively. The chelating interaction was considered as the main adsorption mechanism for metal ions (Cr(III), Mn(II), Pb(II), Cd(II), and Cu(II)). The adsorption capacities of SBA-EDTA and SBA-EDTA/NH2 samples toward studied metal ions were consistent with the Lewis ‘hard and soft acids and bases’ theory. The metal removal efficiency of adsorbents was near 96–92% during three regeneration cycles. All these results indicated that the produced N-functionalized silica were promising for applications in environmental and analytical separation fields.
Highlights
The rapid industrialization, consumer lifestyles, accumulation of Life-of-End products, development of electroplating, metallurgy sludge, newspapers printing, synthetic dyeing and electronics processing industries, the damage caused by heavy metal pollution to the environment water medium is becoming more and more problematic moments [[1], [2]]
The review of literature presented in this paper demonstrates good potential of N-containing ligand-functionalized silica based materials for the selective extraction and separation of heavy metal ions in cationic forms from aqueous solution by adsorption
The study outcomes demonstrated that SBA-ethylenediaminetriacetic acid (EDTA)/NH2 had enough potential toward capture of transition metal ions including Cr(III) from aqueous medium
Summary
The rapid industrialization, consumer lifestyles, accumulation of Life-of-End products, development of electroplating, metallurgy sludge, newspapers printing, synthetic dyeing and electronics processing industries, the damage caused by heavy metal pollution to the environment water medium is becoming more and more problematic moments [[1], [2]]. The heavy metal ions in environmental samples are restricted by some main problems for human healthy They come to the reservoirs from the environment – from rocks, soil erosion, precipitation, ashes of forest fires, etc. Streams from drainage mines are often very acidic, contain high concentrations of dissolved metals and are almost unsuitable for living organisms. They are harmful to the environment because they contain heavy metal ions, which are not subject to biodegradation. Unlike some organic contaminants, such as organochlorine or organophosphorus pesticides, metal ions cannot degrade into less harmful components under natural conditions [[6]]
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