Esra Bilgin Simsek

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).

Heavy Metal Adsorption by Magnetic Hybrid-Sorbent: An Experimental and Theoretical Approach

This study examined the sorption and desorption behaviors of Cu2+ and Pb2+ ions, which were adsorbed on the vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer and magnetic hybrid adsorbent (VBC-DVB-OH-Fe) at pH 5. Batch and fixed bed column experiments were performed to study practical applicability and the breakthrough curves were obtained. The experimental equilibrium data, suitably fitted by the Langmuir and Freundlich isotherms, have shown that ferric oxide loaded magnetic hybrid sorbent (VBC-DVB-OH-Fe) exhibits higher adsorption capacity than vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer. The results indicate the following order to fit the isotherms for both metal ions: Langmuir > Freundlich for polymeric sorbent and Freundlich > Langmuir for VBC-DVB-OH-Fe. The maximum adsorption capacity of VBC-DVB-OH adsorbent is 26.39 mg/g for Pb2+ and 7.93 mg/g for Cu2+ whereas it is increased to 45.81 mg/g for Pb2+and 25.64 mg/g for Cu2+ by using VBC-DVB-OH-Fe adsorbent. A series of column experiments were carried out to determine the breakthrough curves. The regeneration efficiency of the column runs was determined using HCl (10% v/v). The elution efficiency was 90% for each adsorbent.

A comparative study of 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol adsorption onto polymeric, commercial, and carbonaceous adsorbents

AbstractIn this study, polymeric and carbonaceous type of adsorbents were synthesized and their 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) adsorption performances were compared with commercial available XAD-4 resin. Peach stone-based activated carbon (AC) was fabricated by steam activation and porous copolymer of cyanomethyl styrene–divinylbenzene was synthesized by suspension polymerization method. A comparative examination of chlorophenols (CPs) adsorption onto AC, polymeric, and XAD-4 resin was conducted in batch and continuous systems. Zeta potential and potentiometric titration data were analyzed for three adsorbents. The equilibrium data were fitted to the common types of adsorption isotherm and kinetic models. Freundlich model illustrated best fit to the experimental data. The adsorption kinetic obeys the pseudo-second-order model indicating that the chemical sorption is the rate-controlling parameter for chlorophenolic pollutants. The kinetic results...

Equilibrium arsenic adsorption onto metallic oxides : Isotherm models, error analysis and removal mechanism

Arsenic adsorption properties of mono- (Fe or Al) and binary (Fe-Al) metal oxides supported on natural zeolite were investigated at three levels of temperature (298, 318 and 338 K). All data obtained from equilibrium experiments were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, Sips, Toth and Redlich-Peterson isotherms, and error functions were used to predict the best fitting model. The error analysis demonstrated that the As(V) adsorption processes were best described by the Dubinin-Raduskevich model with the lowest sum of normalized error values. According to results, the presence of iron and aluminum oxides in the zeolite network improved the As(V) adsorption capacity of the raw zeolite (ZNa). The X-ray photoelectron spectroscopy (XPS) analyses of ZNa-Fe and ZNa-AlFe samples suggested that the redox reactions are the postulated mechanisms for the adsorption onto them while the adsorption process is followed by surface complexation reactions for ZNa-Al.

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.

Fabrication of Zr-doped TiO2/chitosan composite catalysts with enhanced visible-light-mediated photoactivity for the degradation of Orange II dye

Zirconium/titanium/chitosan (Zr/Ti/CHT) composite catalysts were synthesized by sol-gel method using different chitosan amounts (5-20 wt.%) and their activity in the photocatalytic degradation of Orange II dye was evaluated for the first time. The results were compared with Zr/Ti, Zr/CHT and Ti/CHT catalysts. The composite catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy analysis. XRD analysis revealed that the Zr/Ti/CHT composite catalyst showed high crystallinity of anatase TiO2 phase. Photocatalytic experiments showed that adding CHT into the catalyst structure increased the photocatalytic degradation under visible light irradiation. Also, the first-order reaction rate constant, kapp, was calculated using the Langmuir-Hinshelwood (L-H) equation. The kapp values were found to be 0.009, 0.0013, 0.012 and 0.014 min-1 for Zr/Ti, Zr/CHT, Ti/CHT and Zr/Ti/CHT, respectively. According to stability tests, after the first cycle Orange II dye degradation was found to be 95%, while it was 37% after the fifth cycle. The results showed that the composite catalyst could be used several times for Orange II dye degradation.

Chapter 17 – Boron Uptake from Aqueous Solution by Chelating Adsorbents: A Statistical Experimental Design Approach

Boron removal onto different polymeric ion exchangers was investigated by using response surface methodology (RSM). Box–Behnken experimental design combined with RSM was used to examine and optimize the effects of major process parameters. The quadratic statistical model was defined by three independent variables (pH, temperature, initial boron concentration). The significance of the effects was checked by analysis of variance (statistical software, Statistica 8.0). The optimum values of the selected variables were found by solving the quadratic regression model and analyzing the response surface plots. Nonlinear adsorption isotherm models (Langmuir, Freundlich, Dubinin–Raduskevich, Toth, Sips, Redlich–Peterson) have been performed at optimum conditions.