Equilibrium study, modeling and optimization of model drug adsorption process by sunflower seed shells

The adsorption capacity of the medication methylthioninium chloride (MC) from aqueous solution onto sunflower seed shells (SSS), a low cost and abundant alternative adsorbent, was investigated in a batch system. The surface properties of the adsorbent were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), specific surface area (by using the Brunauer–Emmett–Teller equation), the liquid displacement method and pHPZC. The ability of SSS to remove the medication was assessed through kinetic, thermodynamic and equilibrium investigations. The adsorption efficiency of the SSS adsorbent for the removal of MC was evaluated considering the effects of its concentration, temperature, adsorption contact time, and the pH of the medium. The results obtained from the kinetic and isotherm studies show that the adsorption of the MC on SSS follows pseudo-second-order kinetics (R² > 0.99) and the Temkin isotherm model (R² = 0.97), respectively. The thermodynamic study showed that the adsorption was endothermic and spontaneous, according to its physisorption mechanism. The mathematical modeling of this process was carried out by using the surface response methodology of Box–Behenken. It was possible to deduce a statistically reliable regression equation that related the adsorption yield to the chosen operating parameters, that is, the initial MC concentration, the adsorbent dosage and the pH. Analysis of the variance indicated that the most influential parameters were the SSS dosage, the pH and their interaction and showed the optimal values for ensuring the best adsorption capacity of 95.58%.Xunta de Galicia | Ref. ED431C 2017/47Algerian Ministry of Higher Education and Scientific research | Ref. N: A16N01UN06012019000

Statistical modeling and optimization of Escherichia coli growth parameters for the biological treatment of phenol

peer reviewedAromatic compounds, including phenols, are a significant source of pollution which need to be treated by environmentally-friendly methods, such as bioprocesses. This work focuses on the biodegradation of phenol in a batch reactor with bacteria, and the optimization of the growth parameters in order to obtain the highest phenol degradation. The model and algorithms fitting the growth data are emphasized. Primary models, applied to monitor the dynamic evolution of the microbial biomass of the selected strain, were fitted to the data by nonlinear regression based on the Levenberg Marquart algorithm. The statistically-validated Baranyi and Roberts equation was used to evaluate the growth parameters: maximum growth rate (μmax), latency time (λ), and maximum optical density (ODmax). To improve bacterial growth and phenol degradation performance, physico-chemical conditions, such as initial phenol concentration, pH, and nitrogen source (ammonium sulfate), were optimized using secondary models based on a central composite rotatable design (CCRD). The correlation coefficient, R², for each regression equation is > 94%. The optimal values of growth parameters are λmin = 21.08 h, µmax = 8.68 h–1, and ODmax = 0.39 at pH = 6.3 for an initial concentration of phenol = 200 mg/L and initial concentration of ammonium sulfate = 1.33 g/L. Escherichia coli showed an ability to degrade up to 963 mg/L of phenol in 250 h without prior acclimatization of the strain

Production of modified sunflowers seed shells for the removal of bisphenol A

In this present study, an abundant, available lignocellulosic biomass, sunflower seed shells, SSS, was used as a precursor to prepare an effective eco-adsorbent by treatment with H2SO4. A study of the surface characteristics of raw and acid-treated SSS (ACS) has shown that the addition of H2SO4 greatly affected the physicochemical properties of the obtained eco-adsorbent, improving the BET surface area from 6.106 to 27.145 m2 g−1 and surface oxygen-rich functional groups. Batch experiments were performed to assess the removal efficiency of a phenolic compound, bisphenol A (BPA), on the adsorbents. Several parameters were evaluated and are discussed (contact time, pollutant concentration, adsorbent dosage, and pH), determining that the adsorption efficiency of BPA onto SSS was notably improved, from 20.56% to 87.81% when a sulfuric acid solution was used. Different canonical and stochastic isotherm models were evaluated to predict the experimental behaviour. A dynamic study was performed based on the models of reaction kinetics and those of mass transfer. The results showed that the adsorption kinetics of BPA obey the fractal like-kinetic model of Hill for all experimental conditions. The equilibrium data are well suited to the Hill–Sips isotherm model with a determination coefficient >0.999. The kinetic modelling also indicates that the adsorption processes of BPA onto ACS are exothermic and proceed through a physical mechanism. A mass transfer study, using simplified models, proved that the process is controlled by intraparticle and film resistances to mass transfer of the BPAAlgerian Ministry of Higher Education and Scientifc Research | Ref. A16N01UN060120190001Ministerio de Ciencia, Innovación y Universidades | Ref. CTM2017- 87326-