Ercan Özdemir

Optimization of Process Parameters for Removal of Arsenic Using Activated Carbon-Based Iron-Containing Adsorbents by Response Surface Methodology

In this study, arsenate removal by apricot stone-based activated carbon (IAC) modified with iron (oxy-hydr)oxides was carried out. For this purpose, hybrid adsorbents based on Fe2+-loaded activated carbon (IAC–Fe(II)) and Fe3+-loaded activated carbon (IAC–Fe(III)) were synthesized by precipitation method. A three-level, three-factor Box–Behnken experimental design combined with response surface methodology (RSM) was employed to find the optimum combination of process parameters for maximizing the As(V) adsorption capacity of activated carbon-based iron-containing hybrid adsorbent. Three important operation parameters, namely, initial pH of solution (3.0–7.0), temperature (25–65 °C), and initial As(V) concentration (0.5–8.5 mg L−1), were chosen as the independent variables, while the As(V) adsorption capacities of hybrid adsorbents were designated as dependent variables. Lack of fit test showed that the quadratic model provided the best fit to experimental data for both adsorbents with the highest coefficients of determination (R2), adjusted R2, and p-values for lack of fit. The standardized effects of the independent variables and their interactions were tested by analysis of variance and Pareto chart. The model F-values (FIAC–Fe(II)=330.39 and FIAC–Fe(III)=36.19) and R2 values (R2IAC–Fe(II)=0.9977 and R2IAC–Fe(III)=0.9789) of second-order polynomial regression equations indicated the significance of the regression models. Optimum process conditions for As(V) adsorption onto IAC–Fe(II) were 63.68 °C, pH 3.10, and 8.4 mg L−1 initial arsenic concentration, while 25.22 °C, pH 3.07, and 8.28 mg L−1 initial As(V) concentration were found to be optimum conditions for IAC–Fe(III).

Covalent organic polymer framework with C–C bonds as a fluorescent probe for selective iron detection

A new carbon–carbon bonded nanoporous polymer network was synthesized via efficient and catalyst free Knoevenagel-like condensation polymerization in near quantitative yields. The obtained polymer network, Covalent Organic Polymer – COP-100 possesses strong fluorescent properties and designed solubility in polar aprotic solvents, which shows promise for use as a metal-sensing material in solution. COP-100 exhibited high selectivity towards Fe2+ and Fe3+ in the presence of other common metal cations (Al3+, Ag+, Cd2+, Co2+, Cr3+, Cu2+, Hg2+, Mg2+, Mn2+, Na+, Ni2+, Zn2+) as the fluorescence of the polymer was significantly quenched even at very low concentrations. In the range from 2.5 × 10−6 to 2 × 10−4 M, a linear fluorescence emission response with equipment limited detection minimum of 2.13 × 10−7 M and 2.45 × 10−7 M for Fe2+ and Fe3+, respectively, was observed. These results suggest that COP-100 is a promising material as a selective fluorescence sensor for iron ions.

Direct Access to Primary Amines and Particle Morphology Control in Nanoporous CO2 Sorbents

Chemical tuning of nanoporous, solid sorbents for ideal CO2 binding requires unhindered amine functional groups on the pore walls. Although common for soluble organics, post-synthetic reduction of nitriles in porous networks often fails due to insufficient and irreversible metal hydride penetration. In this study, a nanoporous network with pendant nitrile groups, microsphere morphology was synthesized in large scale. The hollow microspheres were easily decorated with primary amines through in situ reduction by widely available boranes. The CO2 capture capacity of the modified sorbent was increased to up to four times that of the starting nanoporous network with a high heat of adsorption (98 kJ mol-1 ). The surface area can be easily tuned between 1 and 354 m2  g-1 . The average particle size (ca. 50 μm) is also quite suitable for CO2 capture applications, such as those with fluidized beds requiring spheres of micron sizes.

Factorial design analysis of As(V) adsorption onto iron-aluminum binary oxide-doped clinoptilolite

AbstractArsenic adsorption onto an iron-aluminum binary oxide-doped clinoptilolite was studied by using response surface methodology. The Box–Behnken experimental design was used to estimate the effects of major process parameters, namely pH (3–7), temperature (25–65°C), and initial arsenate (As(V)) concentration (0.5–9.5 mg L−1). The experimental data fitted to the empirical second-order model was found to be significant, as was evident from the model F-value of 341.23. The coefficient of determination value of second-order regression model was found to be 0.9977 (Radj = 0.9948), indicating the accuracy and general availability of the model. The initial arsenic concentration of 9.4 mg L−1, pH of 6.0, and temperature f 62.4°C were found to be optimum for maximum As(V) uptake. The results showed that adsorption capacity increased with increasing temperature, indicating the endothermic nature of the adsorption process.

Robust C–C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas

Effective carbon dioxide (CO2) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon–carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile–aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO2 uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO2 solvents, reaching up to 7.8 wt % uptake at 40 °C.