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The adsorption behavior of Allura red (E129) from aqueous solutions onto activated carbon was successfully investigated. All factors affecting the adsorption process were carefully studied and the conditions were optimized. Adsorption of E129 onto activated carbon was found to increase by decreasing the mass of activated carbon, pH and ionic strength of the solution and by increasing temperature. Under the optimum conditions, the maximum adsorption capacity of activated carbon for E129 dye was 72.85 mg.g -1 . Three adsorption isotherm models; Langmuir, Freundlich and Temkin model were investigated regarding E129 adsorption onto activated carbon. The models' parameters KL, qm, R2, and (n) were determined and found to be 0.0222, 72.85 mg.g -1 , 0.9057-0.9984, and 0.992, respectively. Moreover, pseudo first-order and pseudo second-order kinetic models were applied to the adsorption data. The obtained data from adsorption isotherms, kinetic models, and thermodynamic parameters (the free energy change, enthalpy and entropy) indicated that E129 adsorption is spontaneous exothermic heterogeneous adsorption. Furthermore, the results showed that E129 adsorption onto activated carbon obeyed both Freundlich isotherm and pseudo second-order kinetic models.

An innovative and reliable electrochemical sensor was proposed for simple, sensitive and selective determination of F- ions. The sensor is based on the fabrication of porous and electroactive Fe-based metal organic frameworks [MIL-101(Fe)]. It was blended with graphite powder and liquid paraffin oil to from carbon paste electrode (CPE). The MIL-101(Fe)@CPE was characterized using different techniques such as scanning electron microscope, powder X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray, cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry. The MIL-101(Fe)@CPE exhibited two redox peaks (anodic and cathodic) corresponding to Fe3+ and Fe2+, respectively. The determination of F- ions based on the formation of a stable fluoroferric complex with Fe3+/ Fe2+, decreasing the currents of redox species. It was found that the anodic peak current (Ipa) is linearly proportional to the concentration of F- in the range of 0.67-130 µM with a limit of detection (S/N=3) of 0.201 µM. The electrode exhibited good selectivity towards F- detection with no significant interferences from common anions. The as-fabricated sensor was applied for the determination of F- in environmental water samples with recoveries % and RSDs % in the range of 98.1-102.4 % and 2.4-3.7 %, respectively.

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Purpose: To study the adsorption of dye (E120) from aqueous solution onto activated carbon. Method: Factors influencing adsorption were examined and optimized. Three adsorption isotherm models (Langmuir, Freundlich and Temkin) were investigated. Agitation time was set at 72 hours, E120 dye concentration at 10 – 80 mg/L, pH at 7, temperature at 25°C and mass at 125 mg. Results: Adsorption of E120 dye onto activated carbon was enhanced by decreasing the mass of activated carbon, pH and ionic strength of the solution and by increasing the temperature. Under optimal conditions, the maximum adsorption capacity of activated carbon for E120 dye was 10.1 mg/g at 30°C. The model parameters were 0.307 L/mg (KL), 10.1 mg/g (qm), 0.9491 (R2) for the Langmuir isotherm; 2.98 (n), 0.445 mg/g (Kf), and 0.6592 (R2) for Freundlich isotherm; and 4.59 mg/L (A), 2.23 J/mol (B), and 0.5914 (R2) for Temkin isotherm. Thermodynamic studies indicate that the adsorption of E120 dye onto activated carbon is an endothermic process with an adsorption enthalpy (ΔH) of 8.7 KJ/mol. The positive values for ΔG indicate that adsorption was non-spontaneous. The kinetic study of E120 dye adsorption showed that the adsorption process obeyed pseudo-second order kinetics. Conclusion: Commercially available activated carbon, in terms of its physical and chemical characteristics, is a superior adsorbent to other adsorbents mentioned in the literature for removal of toxic dye E120 from aqueous solutions at a high removal capacity.