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Enterobacter cloacae K1 isolated from koala (Phascolarctos cinereus) was used for the simultaneous production of glucose-based biofuels. Genomic analysis showed genes related to bio-2,3-butanediol (BDO), bioethanol (BE), and biohydrogen (BH) production, such as hydrogenase 3, α-acetolactate decarboxylase, α-acetolactate synthase, and three alcohol dehydrogenases. To optimise the multi-biofuel production, a central composite design was applied to assess the effect of glucose concentration, pH, and temperature. Optimal conditions were an initial pH of 9.2, 28.5 °C, and 78.9 g dm−3 glucose, obtaining 22.79 ± 0.32 g dm−3 BDO, 10.8 ± 0.22 g dm−3 BE, and 6378.4 ± 857.8 cm3 dm−3 of BH. Maximum yields of 0.31 g g−1, 0.16 g g−1, and 0.49 mol mol−1 were achieved for BDO, BE, and BH, respectively. The main factor that affected the response variables was the square term of temperature. This work strengthens the novel approach of the simultaneous production of biofuels by using the metabolic abilities of E. cloacae K1. [Display omitted] • First report of multi-biofuel production by E. cloacae K1 isolated from koala. • Butanediol, ethanol, and biohydrogen are the main products obtained from glucose. • Optimal conditions are an initial pH of 9.2, 28.5 °C, and 78.9 g dm−3 glucose. [ABSTRACT FROM AUTHOR]

This study focuses on the development of a novel 0–3 bio-piezoelectric composite utilizing bismuth titanate (Bi 4 Ti 3 O 12) as the piezoelectric ceramic, chitosan as the polymer matrix, and graphene as a doping element. The primary objective of this study was to study the relationship between the mechanical, piezoelectric, and electrical properties within the developed 0–3 bio-piezoelectric composite. By systematically varying the weight percentages of bismuth titanate ceramic and graphene, our aim was to gain a comprehensive understanding of how these variations influence key properties such as young's modulus for flexibility, the piezoelectric coefficient d 33 , electrical conductivity, and voltage output. This exploration was driven by the recognition that these properties are interconnected and crucial for the performance of piezoelectric materials in practical applications. Response surface methodology (RSM) was specifically utilized to model the composite response, optimizing process variables through statistical and mathematical analyses. Through rigorous experimentation and modeling the optimal balance that maximizes conductivity, enhances piezoelectric performance, and ensures reliable voltage generation was determined. The optimum formula selected is the one prepared using a piezoelectric ceramic weight percentage of 35,07 %, and graphene weight percentage of 0.9 % for a harvested voltage equal to 12,05 V. The Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) Images of the optimized composite system revealed the uniform distribution of the fillers in the polymer matrix. The optimized composite design resulting from this systematic investigation holds significant promise for practical applications in energy harvesting and sensor technologies, aligning with the demands of Industry 4.0 and IoT technologies. [ABSTRACT FROM AUTHOR]

The appropriate design of experiments (DoE) could support post-approval lean-stability approaches. A three-factor three-level face-centered design was constructed to evaluate the long-term stability of gliclazide (GLZ) alginate-gelatin beads. The formulation variables were GLZ%(X 1), alginate:gelatin ratio(X 2), and glutaraldehyde%(X 3). The studied responses included GLZ release at predefined intervals in 0.1 N HCl (2 h) followed by phosphate buffer (pH 7.4). Model-dependent and independent approaches were utilized for comparison. DoE-model validation and reduction were implemented. All the studied formulations showed non-significant changes in the particle size (p > 0.05) and most of them showed similar release profiles before and after storage. The directions of the relationships between the factors' main effects and the responses (Y 1 :Q 0.5 h , Y 2 :Q 2h, and Y 3 :Q 4h) remained unchanged after storage. The optimal factor settings based on the proposed optimization criteria were defined. The optimized formulations (OP-1 and OP-2) showed non-significant changes in the particle size after storage. The release profiles and kinetics of OP-1 and OP-2 remained unchanged after storage. No chemical change was indicated (FT-IR). DSC-thermograms of OP-1 indicated GLZ conversion to a more stable polymorph after storage. While OP-2 showed a change in GLZ crystallinity. The stored and fresh beads' surfaces after GLZ release were almost similar. DoE could be utilized to evaluate, optimize, and predict the effects of different formulation variables on the long-term stability of GLZ alginate-gelatin beads. [Display omitted] [ABSTRACT FROM AUTHOR]

In the current study, sulfonic acid functionalized steam-activated char catalyst was prepared from Cocos nucifera (coconut) husk (named as ACH-SO 3 H) at low temperatures for the pre-treatment of Kanuga oil to its methyl ester. This catalyst is attempted reportedly first time for Kanuga oil-derived biodiesel production. An ester yield of 99.51% was achieved over parametric states optimized by response surface methodology of catalyst loading 4.9 wt%, methanol concentration of wt%, for 83 min at 55.75 °C. Based on the proximate analysis, the feedstock Kanuga oil exhibited a high free fatty acid suggesting that the fuel production require the usage of an acid catalyst. Catalyst developed was examined using BET, SEM, EDAX, FTIR, and XRD. Fuel characterization of the produced methyl ester demonstrated that it has physico-chemical properties acceptable for biodiesel according to ASTM standards. The esterification reaction with ACH-SO 3 H exhibited kinetics that resembled pseudo-first-order behaviour, with an Ea of 68.83 kJ mol−1. Endothermic nature and non-spontaneity of the esterification reaction were confirmed through the thermodynamic study. Despite repeated use, the catalyst demonstrated outstanding stability, with the capacity to be reused thrice without notable decay in catalytic action. Catalyst production cost of $6.74/kg was estimated in the work. [Display omitted] • Esterification was carried out to produce biodiesel from Kanuga oil. • Waste Cocos nucifera husk was used for –SO 3 H doped catalyst (ACH-SO 3 H) preparation. • The highest free fatty acid conversion to fatty acid methyl ester was 98.99%. • Esterification was endothermic and non-spontaneous with activation energy of 68.83 kJ mol− 1. • Low catalyst production cost of $6.44/kg validates the economic feasibility of the process. [ABSTRACT FROM AUTHOR]

This study examines the potential of using natural deep eutectic solvents (NADESs) to extract phenolic compounds from propolis and optimizes the extraction process using central composite design (CCD). Different mixtures of NADESs were prepared and analyzed for stability, physicochemical properties, and ability to dissolve phenolic compounds, and four NADES, namely NADES 62 (Betaine, Malic acid and proline 1:1:1, water 15% w/w, NADES 57 (Choline Chloride, Xylitol, Malic Acid 1:1:1, water 15% w/w), NADES 58 (Betaine, Malic acid and proline 1:1, water 15% w/w), NADES 76 (Proline, Citric Acid 2:1 water 15%) were evaluated for the extraction process. The full quadratic model showed that the linear effect of time, temperature, and ultrasound amplitude was found to be significant on the models for NADESs and 80% Ethanol. NADES 62 showed highest extraction yield and the optimal extraction conditions were 80 °C, 135 min, and 100% amplitude. The highest total phenolic and total flavonoid content for NADESs achieved was 5284.2 mg GAE/L and 1531.2 mg QE/L, respectively. With the optimization carried out, the phenolic profile and antimicrobial activity analyses were conducted, has reinforced the information that NADESs can be a good alternative to conventional solvents for propolis extraction. [Display omitted] • Physicochemical and solvent properties of 109 different NADESs were examined. • Process parameters for the extraction of phenolics from propolis were optimized. • Bioactive properties of propolis extracts were compared with conventional solvents. • Phenolic profiles of propolis solutions in NADESs were investigated by LC-MS/MS • Antifungal activities of propolis solutions in NADESs were investigated. [ABSTRACT FROM AUTHOR]

Biological aerated filters (BAF) are attached growth aerobic systems used for the treatment of wastewater. This system can establish the physical filtration of solids along with the biological decomposition of organic matter. The performance of the BAF depends on the type of support media and its ability to meet objective of the treatment process. Natural zeolites, with properties such as ion exchange, larger surface area, capability to form biofilm, adsorption, regenerative properties etc., are a promising filter material in BAF systems. This paper investigates and discusses the effect of various factors like hydraulic retention time (HRT), carbon to nitrogen (C/N) ratio, aeration rate, depth of filter and particle size of natural zeolite which influence the performance of BAF. Based on the experimental results and optimization study using response surface methodology, carried out on the BAF system with varying process variables like HRT, C/N ratio, aeration rate and depth of filter, the natural zeolite media with particle size 1-3 mm range showed improved performance as compared to the coarser particles, that is, 3-5 mm and 5-10 mm. On conducting a final run using natural zeolite particle size of 1-3 mm under optimized value of HRT = 3.25 h, C/N = 6.2, aeration rate = 69 L/h, depth of filter = 83 cm, the BAF system observed chemical oxygen demand, biological oxygen demand, NH3-N, turbidity and total dissolved solids removal percentage of 97%, 96%, 99%, 98% and 58%, respectively. [ABSTRACT FROM AUTHOR]

This study compares hydrothermal and diluted acid-thermal pretreatments at 100 °C for hydrolysate production from Ulva spp. Aiming at bioH 2 production at 55 °C. Three extractants were evaluated in hydrothermal pretreatment: distilled water (H-DW), natural (H-NS) and synthetic seawater (H-SS). The HCl concentration (N), the Ulva spp. Percentage (% w/v), and hydrolysis time (h) in diluted acid-thermal pretreatment were optimised using a central composite design and a desirability function to maximise the total carbohydrate concentration and yield while minimising the HMF and furfural concentration. The hydrolysate from hydrothermal pretreatments, depending on the pretreatment time and % Ulva , achieved bioH 2 production from 20 to 47% lower than the optimised diluted acid-thermal pretreatment (0.3 N HCl, 35% Ulva, and 2.5 h), which was 66.83 (±3.89) NmL g glucose −1. The hydrolysate also indicates potential for lactic acid (HLa) production, resulting in 1.47 molHLa mol glucose −1, before being consumed after 1.6 days and contributing to the bioH 2 production. [Display omitted] • Acid-thermal pretreatment optimisation of HCl concentration, %Ulva and process time. • Desirability function for sugars release maximisation and inhibitor minimisation. • Carbohydrate yield improved in 300%, HMF 10.48 mg L−1 and no furfural. • Optimised hydrolysate generated lactic acid yield of 1.47 mol mol glucose −1. • 66.8 NmL-H 2 g glucose −1 was produced from optimised hydrolysate by mixed culture. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) of light-weight aluminium alloys provides several advantages in the automotive industry due to its wide range of applications such as structural monocoque frames of automobiles, door panels, etc. In this work, an approach to improve the joint properties, by introducing reinforcement material, is attempted. An interlock geometry is created at the sheet metal edges which helps to possess the reinforcement particles. FSW lap welding of interlock aluminum alloys with different grades (AA7075 and AA7475) has been successfully welded in order to achieve higher statistical properties. Central composite design with three level input parameters (tool rotation speeds, weld speeds and wt % of reinforcements) has been used for the design of experiments. Statistical characteristics and microstructural analysis exhibited reduction in grain size of welded joints of aluminum alloys and thereby increased strength of the welded joints. The optimized condition evolved from response surface methodology (RSM) using desirability approach (DA) are tool rotation speed of 1400 rpm, weld traverse speed of 30 mm/sec and reinforcement of 2 wt % SiC p. [ABSTRACT FROM AUTHOR]

Current work aimed to optimize the electrocoagulation (EC) process for the efficient and economic removal of ciprofloxacin (CIP) and levofloxacin (LVX) from aqueous solution via response surface methodology. Four main parameters were selected for the optimisation process, including the initial pH of the solution, initial concentration of antibiotics, operation time, and current density. Subsequently, kinetic and isotherm modelling was performed to characterise the performance behaviour of the EC process at optimum conditions. Based on the results, the EC process achieved a removal efficiency of 92% and 84% for CIP and LVX, respectively, under optimum experimental conditions. The experimental results were consistent with the Langmuir isotherm model for the adsorption of both antibiotics on the iron hydroxide (Fe(OH)3) flocs based on the predicted maximum adsorption capacity of 142 and 185 mg/g, respectively. In addition, the experimental results best fitted the second-order kinetic model with a coefficient of determination (R²) value of 0.986 and 0.992 for CIP and LVX, respectively, implying the chemisorption mechanism controlling the adsorption process. The regression analysis also showed that the experimental results best fitted with the second-order polynomial model with a predicted correlation coefficient (Pred. R²), adjusted correlation coefficient (Adj. R²), and R² of 0.834, 0.941, and 0.967 for CIP; 0.723, 0.908, and 0.952 for LVX, respectively. In short, a comprehensive economic evaluation was performed and the total operational cost over a single run under optimized EC conditions was estimated at $0.490 US/m3. Under optimized EC conditions, the electrical energy consumption and electrode consumption were 3 kWh/m3 and 0.167 kg/m3, respectively, during a single run. [ABSTRACT FROM AUTHOR]

Prickly pear has attracted domestic and international industries' attention owing to its nutritional and health benefit potentials. However, consumption of prickly pear juices is limited by many factors which are addressed essentially through processing methods. The purpose of this study was to compare the effect of clarification by pectinolytic enzymes of Penicillium occitanis coupled with microfiltration (MF) on the physicochemical properties and antioxidant activities of prickly pear juices. The juices were treated with various enzyme concentrations (0.5–5 U/mL), at different times (10–40 min) and temperatures (35–65 °C). The effect of these enzymatic treatments on the viscosity of juices was evaluated using a central composite design. The optimum conditions for the clarification of red fruit juice (RFJ) and green fruit juice (GFJ) were obtained based on surface and contour plots. The optimal treatment conditions were as follows: enzyme concentration 4.75 U/mL, time 37 min and temperature 55 °C for RFJ and enzyme concentration 4.65 U/mL, time 35 min and temperature 55 °C for GFJ. The experimental value of viscosity of the two prickly pear juices was reduced by 34.1% and 30%, respectively which was closely linked to the predicted value (31.79% and 28.93%, respectively). Higher permeate flux and better juice quality were achieved after the enzymatic treatment. The total phenolic and flavonoid contents were correlated with the antioxidant activities. During three months of storage at 4 °C, the clarified juices were microbiologically safe. Our findings showed that the combined pectinolytic enzymes-MF process can be considered as a promising technique that satisfactorily preserves the juice quality. [Display omitted] • Differences in the chemical composition of two prickly pear juices were observed. • The pectinase treatment conditions were optimized by RSM on the viscosity of juices. • The optimized treatment with pectinase was followed by microfiltration (MF). • Clear and stable prickly pear juices were obtained. [ABSTRACT FROM AUTHOR]

In the present study, the immobilization of Trametes versicolor laccase (Tv Lac) was optimized on the synthesized NaY-zeolite by experimental of design. For this purpose, the central composite design was employed to study the effects of the immobilization parameters on the activity of the immobilized Tv Lac on the NaY-zeolite. The optimum conditions were occurred at 2.5 mg/mL of NaY-zeolite concentration, 1 U/mg of enzyme concentration, 1 mM of glutaraldehyde concentration for 4 h immobilization time at 4 °C. In these conditions, the laccase activity developed to 15.68 ± 0.56 U/mg, which was very close to the predicted amount (16.09 ± 1.6 U/mg). Generally, the immobilized Tv Lac showed stability higher than that of the free Tv Lac at the different temperatures and pHs. The activity of the immobilized Tv Lac on the NaY-zeolite was 88.2% and 98.3% after incubation for 120 min at 60 °C and pH 5, respectively. Moreover, the free Tv Lac and immobilized Tv Lac on NaY-zeolite retained about 54.2% and 78.3% of its initial activity after 15 days of storage. The immobilized Tv Lac lost near 20% of its initial activity after 5 cycles of uses. The immobilized Tv Lac exhibited higher efficiency (93.0 ± 1.7% and 80.3 ± 1.8%, respectively) in removal of bromothymol blue (BTB) and trypan blue compared with the free Tv Lac (23.7 ± 1.8% and 15.1 ± 1.5%, respectively). Meanwhile, the kinetic parameters (K m and V max) for immobilized Tv Lac were 0.07 µM and 1.38 µmol/min, respectively, for removal of BTB. Therefore, the immobilized Tv Lac as a good candidate could be suggested for the elimination of dye-containing pollutants due to its high efficiency (more than 80%), which requires further investigations. [Display omitted] • The NaY-zeolite was used for immobilization of Trametes versicolor laccase (Tv Lac). • Central composite design was employed to optimize the immobilization conditions. • Tv Lac was successfully immobilized on NaY-zeolite by IY of 97.22% and IE of 101.04%. • Stabilities and reusability of the immobilized laccase were significantly improved. • The immobilized Tv Lac exhibited high efficiency in removal of BTB. [ABSTRACT FROM AUTHOR]

In this study, magnetic CoFe 2 O 4 nanoparticles (CFO NPs) were fabricated by coprecipitation method for the removal of crystal violet (CV), Cu(II) and Cd(II) from environmental water samples in batch mode. This study investigated the effect of CFO NPs on the removal of CV, Cu(II), and Cd(II) using the response surface methodology (RSM) based on central composite design (CCD). For this purpose, batch experiments were designed and performed to evaluate the effect of variables such as pH, adsorbent amount, sonication time, and concentration of pollutants using RSM. Under optimal conditions (ultrasound time of 17 min, pollutant concentration of 15 mg L−1, CFO NPs amount of 0.24 g, and pH = 6), the removal efficiency was achieved in the range of 95.86–99.82%. Evaluating the reusability of the CFO NPs showed that the CFO NPs adsorbent can be reused for up to 5 cycles while maintaining its high efficiency in removing CV, Cu(II) and Cd(II). The removal efficiency of CV, Cu(II) and Cd(II) was obtained in the range of 91.68–97.59% for real samples. Overall, the results revealed that CFO NPs adsorbent has a high ability to remove CV, Cu(II) and Cd(II) from different water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] This study focused on the preparation, characterization of a supported dicationic ionic liquid nanocomposite (IL@GO@IL NC) and employing of it in the adsorption of Levofloxacin (LVX) and Ciprofloxacin (CPF) antibiotic. Also, the nonlinear least square support vector machine (N-LSSVM), generalized regression neural network (GRNN), along with response surface methodology used for modeling the removal of both antibiotics (i.e. LVX and CPF) from aqueous solution. In this work, the experiments designed based on critical parameters such as adsorbent dose, antibiotic concentration, sonication time and temperature. The nonlinear adsorption isotherms and kinetics models as well as thermodynamic used for fitting the experimental data. The statistical results demonstrated that the LSSVM and GRNN model efficiently predicted the antibiotics removal percentage with very high accuracy, respectively. Furthermore, for an optimal adsorption of LVX and CPF by IL@GO@IL NC, the adsorbent dose, antibiotic concentration, temperature and sonication time should be set to 0.23 and 0.35 g, 95.20 and 100.00 mg L-1, 2.10 and 4.60 min, and 45.00 ℃, for LVX and CPF, respectively. Under these optimal conditions, the removal percentages and adsorption capacity of LVX and CPF will be 98.20 and 97.50%, as well as 730 and 630 mg g−1, respectively. Besides, the IL@GO@IL NC efficiency under optimal conditions drops up by 15% after seven cycles for both antibiotics. Therefore, the IL@GO@IL NC may be considered as a promising option in removing fluoroquinolones antibiotics from water. [ABSTRACT FROM AUTHOR]

This work focuses on the use of biologically produced activated carbon for improving the physico-chemical properties of water samples obtained from the Tigris River. An eco-friendly and lowcost activated carbon was prepared from the Alhagi plant using potassium hydroxide (KOH) as an impregnation agent. The prepared activated carbon was characterised using Fourier-transform infrared spectroscopy to determine the functional groups that exist on the raw material (Alhagi plant) and Alhagi activated carbon (AAC). Scanning electron microscope-energy-dispersive X-ray spectroscope was also used to investigate the surface shape and the elements that compose the powder. Brunauer-Emmett-Teller surface area analysis was used to evaluate the specific surface area and pore size of the prepared AAC. This study investigated three influential variables: activation temperature, activation time and impregnation ratio (IR) (KOH: dried solid wt./wt.). Central composite design was used to determine the interactions between the influential variables. Results show that an activation temperature of 650°C, activation time of 2.5 h and IR of 1:2.6 are optimal for activated carbon preparation. [ABSTRACT FROM AUTHOR]

Marine ecosystems are full of unique microbial phenomena, among them bioluminescence that could be harnessed for different ecological functions. This study was conducted to isolate luminous bacteria and utilize their glowing properties as a potential biosensor for toxicity assessment designs. It is worth noting that this study is the first report on the isolation of an Octopus associated Photobacterium species from Alexandria, Egypt. Based on light intensity, strain Photobacterium sp. EAH3 was selected and identified using 16S-rRNA gene sequencing. The luminescence production was further optimized using experimental. Among eight tested variables, the Plackett-Burman design showed that yeast extract, glycerol, peptone, and NaCl were the most important factors affecting luminescence. The central composite design calculated the optimum concentration of these variables in the optimized medium, which enhanced the bioluminescence activity by 1.39 folds. The employment of Photobacterium sp. EAH3 as a biosensor for the toxicity assessment of some solvents, hydrocarbons and heavy metals was examined using bioluminescence inhibition assay. According to the IC 50 results, the highest toxicity values recorded were 0.004 M, 4.15 ppm and 1.4 ppm for isoamyl alcohol, Hg2+ and catechol, respectively. Moreover, our study sheds light on futuristic methodology for monitoring toxicity in real polluted environmental and effluents' samples reflecting its promising efficiency. [ABSTRACT FROM AUTHOR]

In heat exchangers, solar collectors, and geophysical transport, the temperature difference is significant, so the linear form of the density-temperature approximation (the Boussinesq approximation) is inadequate to describe actual density variations. Thus, the current study took into account the effect of nonlinear buoyancy on the thermal performance of a homogeneous nanofluid with hybrid nanoparticles in a free convective inclined energy system. In addition, response surface methodology with central composite design (RSM-CCD) is implemented to build a quadratic model based on three factors and levels (Ha , α , ϕ). To perform thermal evaluation, the experimental correlations are utilized with dimensionless controlling parameters such as Rayleigh number (Ra = 10 3 to 10 6), Hartmann number (Ha = 0 to 50), nanoparticle volume fraction (ϕ = 0 to 0.02) and angle of inclination (α = 0 to π) using Galerkin finite element method (GFEM) with a refined mesh (degree of freedoms (DOFs) = 208977, domain elements = 25636 and boundary elements = 858) for grid independent results. According to RSM-CCD, the Hartmann number has a significant impact on the thermal behavior of energy system. Also, the maximum average Nusselt number (Nur = 5.4938) is achieved with the optimal combination of key parameters i.e., Ha = 36.707 , α = 0.5236 and ϕ = 0.001. [ABSTRACT FROM AUTHOR]

The study investigated the supercritical ethanol liquefaction of bamboo leaves using a functionalized reduced graphene oxide catalyst (GO r). The ZrO 2 –SrO/GO r catalyst consisted mostly of mesopores (95%) with only 5% micropores, which enhances the reactant's accessibility to active sites. The supercritical ethanol liquefaction was carried out in a 150 mL reactor and optimised for bio-oil production using an experimental central composite design (CCD). At optimum operating conditions (375 °C, a catalyst-to-biomass ratio of 1:2.5 (wt:wt) and a biomass-to-ethanol ratio of 1:10 (wt/vol), the bio-oil yield derived from bamboo leaves was 47%, which was higher than hydrothermal process (27%). A model was developed from analysis of variance (ANOVA) and validated using experimental data. The predicted and experimental data agreed well with an R2 of 0.99. The bio-oil had a higher heating value of 35.3 MJ/kg, consisting mainly of esters, phenolic and hydrocarbon compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

• Capacitive deionization (CDI) was conducted using activated carbon cloth electrodes. • The operational parameters for the CDI process was investigated using expert software. • Three parameters were used for CDI prediction and optimization. • A quadratic model was obtained and used to predict and optimize the process. • Model's validity was confirmed with different water sources using optimized parameters. Researchers have widely explored capacitive deionization (CDI) for brackish water desalination over the last decade, considering it a promising technology. Theoretical and statistical analyses are crucial for optimizing CDI performance parameters. This study utilizes response surface methodology (RSM) with central composite design (CCD) to systematically explore the impacts of crucial operational variables on CDI efficiency. Our analysis yielded a robust quadratic model with a high R-squared value (0.99), indicating excellent predictive capability. The CDI performance was conducted using activated carbon cloth electrodes and achieved a maximum removal efficiency of 40.6 % under optimal conditions of 1.8 DC V, 2 ml/min, and 500 mg/L NaCl. The increase in applied potential enhanced removal efficiency, whereas flow rate and NaCl concentration had adverse effects. The validity of the resulting model was further tested with various water sources such as groundwater and produced water, demonstrating its predictive capability when a pretreatment step is included. However, we recommend developing a new model for more robust optimization of CDI systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV-irradiated homogeneous Cr(III)-Fenton-like reaction reported for the first time. • Gallic acid degraded at neutral pH via Cr(III)-mediated photo-Fenton-like reaction. • Solution pH has the most significant impact on TOC removal in Cr-Fenton process. • Effects of operating variables in Cr-photo-Fenton studied via experimental designs. • Gallic acid transformation products are identified by HPLC-MS/MS. This study aims to utilize the chromium present in tannery wastewaters as a catalyst of photo-Fenton-like reaction. Gallic acid (GA), a monomer of tannic acid, was chosen as a model compound due to its recalcitrance and toxicity. A 2k factorial design followed by a central composite design was applied to evaluate the effects of H 2 O 2 and Cr(III) concentrations, and pH on total organic carbon (TOC) removal. Statistical analysis showed all variables significantly influenced TOC removal, developing a second-order polynomial model (R2 = 0.8502, R adj 2 = 0.7967, F-value = 15.89, p-value < 0.0001, lack of fit = 0.24). The most favorable conditions were [H 2 O 2 ] > 35 mM, [Cr(III)] > 130 mg L−1, and pH 6.5–7.0, achieving up to 26 % TOC removal in 120 min. UV–vis and LC-MS confirmed GA degradation; although, the byproducts generated would be very recalcitrant or would inhibit the catalytic action of Cr(III), limiting the TOC removal. [ABSTRACT FROM AUTHOR]