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-

Green Synthesis of N/Zr Co-Doped TiO2 for Photocatalytic Degradation of p-Nitrophenol in Wastewater

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g-1 vs. 50 m2 g-1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light