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In this study, activated carbon (AC) obtained with apple peel was used for removal of Neutral Red (NR) from aqueous solutions. The characterization of AC was evaluated with the Brunauer-Emmett-Teller (BET), Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analyses. Isotherm, kinetic, and thermodynamic parameters were determined for NR removal with AC. Eighteen isotherm models and eight kinetic models were analyzed for three temperatures and six initial dye concentrations. The experimental data best agree with the Langmuir model among the isotherm models, and the maximum adsorption capacity (qm) was calculated 142.857 mg/g at 318 K. It was determined that the pseudo-second-order (PSO) model was the best choice among the kinetic models with the highest correlation coefficients. The removal percentage of NR dye with AC obtained 82.13%, 84.79%, and 87.20% for 120 mg/L initial dye concentration at 298 K, 308 K, and 318 K, respectively. The negative free energy, enthalpy, and entropy values of adsorption obtained − 6386 J/mol, 46280 J/mol, and 165.48 J/mol.K for 20 mg/L NR concentration at 318 K, respectively. The results of this separation process shown spontaneous essence, and workability coinciding with the negative free energy and activation energy was found 13.651 kJ/mol. The assessment of the isotherm, kinetic, and thermodynamic results were evaluated with error functions. The highest correlation coefficient (R2) values and the lowest sum of squares (SS), sum of the square of error (SE), and mean square of error (MSE) values were determined with Langmuir isotherm and PSO kinetic models. This research showed that AC prepared from biomass can be used effectively for wastewater treatment using adsorption technique. [ABSTRACT FROM AUTHOR]

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In this study, pinecone sawdust (PCS) performance was investigated for Basic Red 46 (BR 46) dye adsorption from aqueous solutions. The physicochemical and morphological characterization of PCS before and after BR 46 adsorption were evaluated with the help of Fourier transform infrared spectra, X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis. Effects of initial dye concentration, temperature and contact time were determined for BR 46 adsorption. Seventeen equilibrium isotherm models and eight kinetic models were compared at 298 K, 308 K and 318 K temperatures for five different concentrations which varied from 20 to 60 mg/L. The obtained adsorption data best-fit the Freundlich model among all the applied isotherm models, and the maximum adsorption capacity (qm) was calculated as 129.87 mg/g at 298 K. The pseudo-second-order model was the best choice to describe the adsorption behavior among all the applied kinetic models. The removal percentage of BR 46 dye with PCS was 74.52% at 318 K for 60 mg/L concentration. The negative free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) values of adsorption were calculated as − 2837 kJ/mol, 18,898 kJ/mol and 68.51 J/mol K, respectively. This adsorption process was spontaneous and favorable, coinciding with the negative free energy. The activation energy (EA) value of this process was determined with the Arrhenius equation as 19.92 kJ/mol. The reliability of all results was analyzed statistically and evaluated with correlation coefficient (R2), sum of squares, sum of the square of error and mean square of error values. As a result of this study, PCS can be used effectively for BR 46 dye removal. [ABSTRACT FROM AUTHOR]

In our study, medium conditions were optimized for percent chemical oxygen demand (COD) reduction and drug removal from diclofenac sodium (DFS) solutions. Response surface methodology/central composite design was used for optimization. A. Campestris/Amberlite Styrene–divinylbenzene (XAD-4) biocomposite material was used as adsorbent. Four independent parameters (pH, initial concentration, interaction time and adsorbent amount) were chosen to optimize both % COD reduction and DFS removal. As a result of experiments, maximum 77% COD reduction and maximum 98% DFS removal were obtained at 4 pH, 225 mg/L initial concentration, 36 min and 0.69 adsorbent amount. Scanning electron microscope and Fourier transform infrared spectroscopy devices were used for characterization of adsorbent material. To identify the isotherm for the adsorption mechanism, the Langmuir, Freundlich, Temkin and Harkins–Jura isotherm equations were examined. The Freundlich isotherm had 96.2% regression coefficient (R2) and was linear, so had better fit compared to the other equations and the adsorption mechanism abided by the Freundlich isotherm. The results show that statistical optimization design was successfully applied to experiments and A. Campestris/Amberlite XAD-4 is an appropriate biocomposite adsorbent with specific affinity for % COD reduction and removal of DFS from aqueous solutions under optimal conditions. [ABSTRACT FROM AUTHOR]