In this study, the removal of Cr(VI) from aqueous solution by modified zeolite with 3-aminopropyltriethoxysilane was investigated. The effect of various parameters such as pH, contact time, temperature, initial concentration of Cr(VI) ion, common cations, and anions on the adsorption of Cr(VI) was studied. The modified zeolite was characterized by following instrumental analysis of XRD, SEM/EDS, BET, and FT-IR. Based on calculated thermodynamic parameters values (∆G 0 < 0, ∆H 0 > 0, and ∆S 0 > 0) and kinetic properties of the adsorption of Cr(VI) by modified zeolite, it was concluded that the ratelimiting step of the process is a second-order chemical reaction. The results of the adsorption isotherm study confirmed that the adsorption follows the Langmuir isotherm model. The maximum adsorption capacity was 13.5 mg/g.
In this work, we removed copper (II) from an aqueous solution by using zeolite modified with a silicon-organic monomer (3-aminopropyltriethoxysilane; APTES) depending on the pH, time, temperature, and initial concentration of Cu(II) ions. To confirm the modification process and assess the interaction between the modified zeolite and Cu(II), we performed instrumental analyses (XRD, SEM/EDX, TGA/DTA, BET, FT-IR, and XPS). We determined the maximum adsorption capacities of the modified zeolite for Cu(II) to be 4.50, 6.244, 6.96, and 20.66 mg/g at T = 25 °C (pH = 5, t = 8 h) when the initial concentrations of Cu(II) were 50, 100, 200, and 400 mg/L, respectively. According to the adsorption thermodynamics and kinetics, the second-order reaction controls the adsorption process. Based on the two isotherm models (Langmuir and Freundlich) with constant values (KL = 0.144, n = 2.764) and the correlation coefficients (R2 = 0.8946, R2 = 0.9216), we concluded that the Cu(II) adsorption onto the modified zeolite could be followed by the Freundlich isotherm model rather than the Langmuir isotherm model. The modified zeolite could be an effective material for the removal of Cu(II) from aqueous solutions.
In this research work, a new type of absorbent material was obtained using kaolin which is produced by clay of the "Tsogt-Ovoo" deposit in Umnogovi province. The kaolin was produced by removing its mechanical impurities from clay and treating it to acid and heat treatment. When producing a chitosan based new absorbent bead, pure chitosan and mixtures of chitosan and kaolin (8:1, 8:2 and 8:3) with certain ratios were subjected to chemical processing. It was determined that the absorption capacity of chromium ion (Cr(VI)) was the highest when chitosan and kaolin mass ratio was 8:2. The adsorption activity of Cr(VI)in chitosan-based adsorbent was studied depending on the pH of the solution, time, temperature, initial concentration of chromium ion solution and mass of adsorbent material. The degree of absorption was the highest (80.25%) when initial concentration of thechromium ion solution is 50 mg/l, temperature is 250C, contact time is 3h and the mass of the adsorbent material is 0.1 g. It shows that this chitosan based adsorbent bead can be used for the separation of chromium (Cr(VI)) from aqueous solutions. Читосан суурьтай шинэ материалын +6 валенттай хром шингээх идэвхийн судалгаа Хураангуй: Тус судалгааны ажлын хүрээнд Өмнөговь аймгийн нутагт орших “Цогт-Овоо” ордын шаврын дээжийг механик хольцоос салган, хүчлийн ба дулааны боловсруулалтад оруулж бэлтгэсэн каолиныг ашиглан шинэ төрлийн шингээгч материал гарган авав. Читосан суурьтай, үрэл хэлбэрийн шинэ төрлийн шингээгч материалыг гарган авахдаа цэвэр читосан болон тодорхой харьцаа бүхий читосан ба каолины (8:1, 8:2 ба 8:3) хольцыг химийн боловсруулалтад оруулж гарган авсан. Туршилтаар 8:2 массын харьцаа бүхий читосан ба каолинын хольцыг ашиглан гарган авсан үрэл хэлбэрийн шингээгч материалын +6 валенттай хром (Cr(VI)) шингээх шингээлтийн багтаамж хамгийн өндөр болохыг тогтоов. Читосан суурьтай шинэ төрлийн шингээгч материалын усан уусмалаас Cr(VI) шингээх идэвхийг уусмалын рН, хугацаа, температур, хромын уусмалын анхны концентраци ба шингээгч материалын массаас хамааруулан судалж үзэхэд уусмалын орчин pH 3, шингээлтийн хугацаа 3 цаг, шингээлтийн температур T= 25℃, хромын уусмалын анхны концентраци 50 мг/л, шингээгч материалын масс 0.1 г байх нөхцөлд шингээлтийн зэрэг хамгийн өндөр буюу 80.25% байна. Энэхүү шинэ материалыг усан уусмалаас хромыг (Cr(VI)) ялгахад ашиглах боломжтой гэж үзэж байна. Түлхүүр үг: адбсорбент, металлын ион, усан орчин, шингээлтийн багтаамж
In this study, the sorptions of Cu(II), Pb(II), and Cr(VI) on amine-functionalized activated carbon were investigated. Coal from the Tavantolgoi deposit of Mongolia was used as a precursor for the modification. After the coal carbonization, the char was activated with heated steam at different times (120, 180, and 240 min) and several temperatures (800ºC and 850ºC). The activated carbon at 850ºC for 240 min was used for the treatment with 3-aminopropyltriethoxysilane (APTES). The interactions between metal ions and functional groups on the sorbent surface were confirmed by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDS). The influence of various parameters such as pH (2-7), contact time (0.5-6 h), temperature (25ºC, 35ºC, 45ºC, and 55ºC), initial concentration of heavy metals ions (10, 25, and 50 mg/L), and common cations (Na + , K + , Ca 2+ , Mg 2+ ) was investigated. The optimum pH for Cu(II), Pb(II), and Cr(VI) sorption on the modified activated carbon was chosen as 4, 3, and 3, respectively. The sorption capacity was increased from 6.15 to 9.88 mg/g and 17.1 mg/g to 19.0 mg/g when increased the temperature from 25ºC to 55ºC for Cu(II) and Cr(VI) adsorption, respectively (initial concentration of metal ions were 50 mg/L). But the sorption capacity was decreased from 3.13 mg/g to 2.69 mg/g when increased the temperature from 25ºC to 55ºC for Pb(II) adsorption. The thermodynamic parameters such as enthalpy (ΔHº), entropy (ΔSº), and Gibb's free energy (ΔGº) were estimated, and the results confirmed that all sorption processes are spontaneous and thermodynamically favorable. The sorption capacity was decreased when the amount of Na + , K + , Ca 2+ , or Mg 2+ increased from 0 to 200 mg/L, and a remarkable decrease in sorption capacity was observed for Pb(II) adsorption. The order of adsorption capacity of modified activated carbon for metal ions was Cr(VI) Cu(II) Pb(II). The sorption mechanism was discussed for the processes.
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