Zirconium-Loaded Mesostructured Silica Nanoparticles Adsorbent for Removal of Hexavalent Chromium from Aqueous Solution

Abstract

Zirconium-loaded mesostructured silica nanoparticles (Zr/MSN) were developed for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. X-ray diffraction, transmission electron microscopy, and Brunauer− Emmett−Teller results revealed that both MSN and Zr/MSN showed a characteristic highly ordered hexagonal pore structure with a high specific area of 821−1219 m 2 g −1 . Fourier transform infrared analysis showed that the presence of Zr diminished the absorbance band that was assigned to silanol groups of the structural defect sites, while XPS analysis of the binding energy of Si−O−Zr indicated interactions between the silanol groups and zirconium. The interaction of zirconium and silanol groups from the structural defect sites generated bidentate zirconium, which acted as an active site for the adsorption. The experimental results showed that the modification of MSN with zirconium significantly enhanced the adsorption capacity for Cr(VI). The equilibrium isotherm data showed that the adsorption process was best described by the Langmuir isotherm with 104 mg g −1 maximum adsorption capacity, while the kinetics of Cr(VI) adsorption followed a pseudo-second-order kinetic model. The thermodynamic properties confirmed that the adsorption of Cr(VI) onto Zr/MSN was spontaneous and endothermic in nature, with an activation energy of 24 kJ mol −1 showing that the adsorption was a chemisorption process.

Highly efficient removal of hexavalent chromium using hexagonal disc shaped barium hydrogen phosphate

“…This may also cause increased hindrance to the diffusion of Cr (VI) ions in the presence of large numbers of OH −. 61 The adsorption of hexavalent chromium on BaHPO 4 surface occurred via electrostatic attraction between Cr(VI) anionic species and the cationic barium as shown in Figure 8b.…”

“…The increase in adsorption capacity with temperature is due to the either an increase in the number of active surface sites available for adsorption on the adsorbent or an increase in the diffusion rate of ions. Thermodynamic parameters such as changes in enthalpy , entropy and Gibbs free energy were calculated using the following Equations 61 : where R and T are the ideal gas constant [8.314 J/(mol·K)] and the temperature [K], respectively K c is the ratio of Cr (VI) adsorbed on the adsorbent to Cr (VI) remaining in solution after 3 h of adsorption process, R is the gas constant (8.314 J/mol K), and T is the absolute temperature ( K ), The Equation is known as the van't Hoff equation, straight line fitting on the graph versus 1/T (Figure 8d) gives values of enthalpy , entropy given in the Table 4. is negative and magnitude increases with the rise in the temperature indicating that adsorption of Cr (VI) occurs spontaneously and is more favorable at high temperature.…”

“…Negative charges on Cr (VI) and BaHPO 4 increase Columbic repulsion forces, resulting in a decrease in adsorption capacity as pH rises. This may also cause increased hindrance to the diffusion of Cr (VI) ions in the presence of large numbers of OH À 61. The adsorption of hexavalent chromium on BaHPO 4 surface occurred via electrostatic attraction between Cr(VI) anionic species and the cationic barium as shown in Figure8b.The temperature dependence of adsorption of Cr (VI) was studied at pH = 6, 50 ml of 50 ppm Cr (VI) solution, adsorbent dose = 10 mg and stirring time 3 h. Cr (VI) adsorption capacity increases with an…”

Efficient Removal of Cr(VI) Ions by a Novel Magnetic 4-Vinyl Pyridine Grafted Ni3Si2O5(OH)4 Multiwalled Nanotube

“… 77 , 78 The negative values of the free-energy changes (Δ G ) confirm that the adsorption of Cr(VI) on the adsorbents is spontaneous and favorable in the whole considered temperature range. 79 The Cr(VI) adsorption is more favorable at higher temperature since the free-energy change at higher temperature is more negative. 80 The positive value of Δ H indicates that Cr(VI) adsorption is endothermic and the Cr(VI) uptake increases with increasing temperature of the solution.…”

2018 International Conference of Chemical Engineering and Industrial Biotechnology (ICCEIB) Preface

“…In the research related to recent trends in the area of separation, Lam et al augmented microwave pyrolysis with steam activation to convert palm kernel shell into activated carbon (AC), subsequently tested as an adsorbent to remove herbicide 2,4-dichlorophenoxyacetic (adsorbed up to 11 mg of herbicide/g of AC) from contaminated surface water in agricultural land. Triwahyono et al developed zirconium-loaded mesostructured silica nanoparticles (Zr/MSN) for the removal of hexavalent chromium (Cr­(VI)) from aqueous solutions with a reported 104 mg/g maximum adsorption capacity. Ahmad et al report on the investigation of emulsion stability, membrane breakage, and emulsion swelling of emulsion liquid membranes for acetaminophen removal.…”