The rising level of Carbon Dioxide (CO2) concentration and the growing energy demand of the world have given a desperate necessity of carbon-neutral and sustainable energy sources. Carbon Capture, Utilization and Storage (CCUS), especially CO2-Enhanced Gas Recovery (CO2-EGR) has become an attractive technology to maximize hydrocarbon recovery with a minimal environmental impact. The paper introduces an AI-based system of recovering carbon-neutral gas by implementing CO2 gas injection and storage. A number of supervised learning models, including XGBoost, Random Forest (RF), and a hybrid RF-XGBoost, were used in conjunction with data preprocessing and feature engineering to come up with the results from the NETL CCS dataset. They also use Bayesian Optimization to adjust the parameters. The findings reveal that the hybrid model does better than the individual models because it has the lowest MAE (0.080), MSE (0.011), and RMSE (0.105), as well as the highest value of R2 (0.96). Further, the recovery efficiency increases by 83 to 92 percent, the leakage risk is lowered by 0.14 to 0.06, and the cost of operation is lowered by 1.00 to 0.72. The results indicate that AI-based strategies are effective to maximize the efficiency, safety, and sustainability with a carbon-neutral gas recovery system.
Petroleum refinery wastewater (PRW) is becoming a big problem for both people and the environment, so researchers have been trying harder to find better ways to treat it. One option that looks really promising is using advanced oxidation processes (AOPs) to break down all the pollutants inside this wastewater. In this study, new-designed photoreactor was used to conduct a photocatalysis approach that aimed to remove the chemical oxygen demand (COD) from PRW collected from Al-Diwaniya refinery in the south of Iraq. The geometrically optimized photoreactor enhances the formation of the free radicals required for efficient degradation by maximizing mass transfer and light dispersion. Bare TiO₂ and SiO₂/TiO₂ were fabricated as photocatalysts with the sol-gel technique and then examined by the XRD, FTIR, FESEM, AFM, BET, UV-DRS, and PL analysis. Results showed that, the optimal SiO₂/TiO₂ ratio was 5/95% (S-5) achieving 90% COD reduction efficiency with a photocatalyst dosage of 2 g/L, a reaction time of about 4 h, and using 8 UV-C lamps (8 W each). Under these conditions the process consumed 0.512 kWh/L electricity energy (EE/O). The results demonstrated that COD reduction exhibits behavior consistent with pseudo first order kinetics. In addition, the scavenger experiments revealed that the COD was primarily degraded by the ⦁O₂- radical. After five cycles, the photocatalyst S-5 maintained its stability and continued to remove over 82% of the COD. Refinery effluent was significantly better treated after using this innovative reactor design in conjunction with the SiO₂/TiO₂ photocatalyst. It provides an ecological, more efficient, and less expensive way to lower COD in PRW.
The paper introduces a state-of-the-art Physics Augmented Machine Learning framework to predict the critical geomechanical property – Unconfined Compressive Strength (UCS) – in the Zubair reservoir of the Zubair field for mitigating the risk of CO2 storage. The geomechanical results and modeling workflow were obtained via an integrated software system that was developed in Python, while all computational processes and model training were conducted in the Deepnote interactive cloud computing environment; thus, all of the necessary libraries and the high-performance processing capacities were seamlessly integrated. Through the comparison of six ensemble algorithms which are Categorical Boosting (CatBoost), XGBoost )Extreme Gradient Boosting(, RF(Random Forest Regressor), ExtraTrees (Extremely Randomized Trees), GBM (Gradient Boosting Machine), and Deep ANN (Deep Artificial Neural Networks), the research determined the most dependable models, while the Gradient Boosting model stood out by achieving UCS prediction with the best metrics of (R2=0.9995, MAE=3.64). The models are not only providing a precise and reliable but also a scalable assessment tool for subsurface stability, containment integrity, and real-time reservoir monitoring.
Nanoporous-SnO₂ films were electrochemically prepared via anodizing of metallic tin electrodeposited on a cylindrical copper substrate using rotating cylinder electrode Technique. The effects of anodizing potential (4-7V), oxalic acid (OA) concentration (0.1-0.5M), time (10-20), and rotation speed (150-450 rpm) on the electrochemical activity of SnO2 as an anode in degrading methylene blue (MB) were investigated. Results showed that increasing oxalic acid concentration gives better performance in degrading MB while increasing anodizing potential enhanced the electrode activity up to a potential of 5 V beyond which no enhancement of electrode activity towared MB degradation was noted. Longer time of anodizing has opposite effect while rotation speed enhanced the electrocatalytic activity of SnO2. The best conditions of anodizing were potential of 5 V, 0.4M OA, 15 min, and 250 rpm in which MB removal was 87.6%. Structural morphology of SnO2 prepared at the optimum conditions confirmed the conversion of tin to SnO2 with free crack structure. These results demonstrate that adopting anodizing method with rotating cylinder technique to forming SnO2 anodes is a promising strategy for constructing high-performance anodes suitable for treatment wastewaters.
Given the environmental and health risks posed by sulfur pollutants, their removal and the production of lower sulfur hydrocarbon fuels are essential. Therefore, oxidative desulfurization (ODS) technology has become crucial as it operates efficiently under moderate conditions. This study focused on the synthesis of a (Fe₂O₃ + NiO)/SiO₂ catalyst via incipient wetness impregnation, followed by drying at 120°C and calcination at 600°C. Several tests were performed on the catalyst before its application: BET, TGA, and SEM-EDX. The BET results showed a decrease in surface area from 166.47 to 149.57 m² g⁻¹ after metal loading, confirming the fixation of iron and nickel oxides on the silica support. XRD and FTIR analyses confirmed the formation of the metal oxide phases Fe₂O₃ and NiO, while preserving the amorphous nature of the silica. The prepared catalyst was tested in ultrasonic oxidative desulfurization of real diesel fuel containing up to 2018.14 ppm using hydrogen peroxide as the oxidizing agent. Various conditions were investigated, including the effect of temperature (25–75°C), reaction time (30–60 minutes), and ultrasonic intensity (80–100%). This was followed by ethanol extraction at a 1:1 diesel-to-solvent ratio. A sulfur removal efficiency of 90% was achieved. The study showed that the reaction followed a pseudo-first-order model with reaction rate constants of 0.0172, 0.0252, and 0.0400 min⁻¹ at 25, 50, and 75°C, respectively, with R2 =0.98. The activation energy of the reaction was also calculated and found to be 14.50 kJ mol⁻¹, indicating the suitability of the kinetics and the efficiency of the catalytic activity under the influence of ultrasonication.
Conversion of waste tires and date stones into char through co-pyrolysis is an effective way to safely remove and recycle these materials. This study tested char as a low-cost adsorbent for removing nitrate and phosphate in fixed-bed systems, offering a way to reuse waste tires and date stones. The effects of inlet pollutant concentration (50, 150, and 300 mg/L), flow rate (5, 10, and 15 ml/min), and bed height (5, 10, and 15 cm) on the adsorption system’s breakthrough were measured. Characteristics of char were analyzed via the Fourier transform of infrared (FTIR), Brunauer-Emmett-Teller (BET), and zeta potential. The fixed-bed analysis demonstrated superior correlation of breakthrough data with both the Yoon-Nelson and Thomas models. Under varying circumstances, the findings agreed with the Yoon-Nelson and Thomas models, as measured by the correlation coefficient R2 values (0.8147-0.9913) for phosphate, (0.9187-0.9913) for nitrate, and (0.8146-0.9907) for phosphate, (0.9189-0.9801) for nitrate, respectively. The results demonstrate the potential of the prepared char as an efficient and sustainable adsorbent for nutrient removal in continuous treatment systems, providing a promising approach for wastewater treatment and waste valorization.
Aqueous mineral carbonation is one of the most important methods of permanent CO2 sequestration in Carbon Capture, Utilization, and Storage (CCUS). This is carried out using alkaline pH-risers to neutralize the acidity of carbonic acid (H2CO3) to cause a change in the chemical balance to carbonate ions (CO32-). This paper assesses the different sources of alkalinity with special reference to the performance of caustic soda (NaOH) and soda ash (Na2CO3) under industrial circumstances. It has been shown in experiments that caustic soda is the most effective reagent in quick mineralization. It causes a sudden early increase in pH (about 2.0 to 2.5 units per gram) and maintains a very alkaline pH (pH >12), which are critical to the efficiency of CO2 absorption (95.52 %). Moreover, NaOH has a remarkable stability at high pressure and the rate of change in pH (0.3 ΔpH/gm) does not change at the pressure of 65 bars. Soda ash on the other hand is a moderate buffer that reaches its highest pH at approximately 11.6, with an easily lower absorption efficiency of 72.45%. Soda ash performance improves as the pressure is increased to conserve pressure up to 65 bar, thus making it difficult to use it in high-pressure systems. Optimization of the industry shows that the efficiency is maximized within the temperature regime between 40°C and 60°C, where the accelerated reaction rates resulting decrease in the gas solubility. Furthermore, the best mass transfer rate is 300 rpm that minimizes the CO2 bubble size. Though the stoichiometric superiority of caustic soda 1.0 kg does the work of 1.3 kg of soda ash, it presents severe challenges to operation because of its expensive nature, energy-consuming nature, and corrosivity. Soda ash is also still a feasible option in large scale sequestration due to its 30-40 % lower cost and the fact that it is dry and can be transported easily. Finally, a tradeoff between chemical reactivity, mechanical stability, and scalability of the economic side should be made even in the choice of a pH riser.
This study demonstrates a sustainable, "trash-to-treasure" approach by synthesizing silica (SiO2) and alumina (Al2O3) nanoparticles (30–80 nm) from local waste materials—specifically bentonite clay and aluminum wire waste—and evaluating their performance as eco-friendly additives in 350 mL water-based drilling fluids at concentrations ranging from 0 to 1 g. Tested under harsh subsurface conditions, the incorporated nanoparticles significantly enhanced the fluids' rheological properties, lubricity, filtration control, and swelling inhibition, with performance scaling alongside nanoparticle concentration. Notably, at a 1 g dosage, the fluid's yield point spiked from a baseline of 9 to 42 for SiO2 and 32 for (Al2O3), while high-pressure high-temperature (HPHT) fluid loss was reduced from 21 mL to 14.6 mL (SiO2) and 16.4 mL (Al2O3) due to the formation of a low-permeability filter cake. Furthermore, a 0.75 g dosage lowered the coefficient of friction from 0.45 to 0.35 (SiO2) and 0.37 (Al2O3), while effectively mitigating clay swelling (SiO2) showing superior inhibition at lower concentrations), ultimately proving that these waste-derived nanoparticles offer a highly effective, cost-efficient, and environmentally friendly alternative to commercial drilling mud additives.
The cost of raw materials and the production process remain major challenges hindering the expansion of biodiesel production on a large scale. Several technologies have been developed to reduce production costs. This research aims to investigate the energy recovery and economic aspects of biodiesel production from used cooking oil (WCO) using conventional and microwave (batch and continuous) transesterification technology. Used cooking oils are an alternative source of energy, given their high potential for use in biofuels production, especially biodiesel. The production of biodiesel in this study relies on a basic esterification reaction using calcium oxide prepared from willow leaves as a catalyst. The results showed that the optimal operating conditions include a catalyst concentration of 3% wt.%, a methanol content of up to 70wt%, and an operating temperature of 65 °C. The reaction time varied depending on the heating technique; the conventional method required 90 minutes, while the time decreased to 20 minutes with batch microwave heating, and to only 5 minutes with continuous microwave heating. These conditions resulted in the highest biodiesel yields of 93.852%, 96.313%, and 93.43%, respectively, for the three methods. From an economic perspective, the cost of producing one liter of biodiesel for conventional and microwave heating (batch and continuous) was approximately 1074.190, 483.588, and 510.162 Iraqi dinars/liter, respectively. The analysis also showed that the total energy consumption of the three methods was 0.945, 0.026666 and 0.03433 kWh respectively, demonstrating that microwave technologies offer a significant reduction in reaction time and higher energy efficiency, thus potentially leading to greater economic returns and operational benefits compared to traditional methods. Finally, the findings result calculated the energy payback period for producing 1 liter of biodiesel using microwave technology. The results showed that the system is sustainable, making it a suitable means of reducing the cost of biodiesel production and supporting its future commercialization.
The performance of pomegranate peel treated with oleic acid (PPOA) was studied using a batch mode for ciprofloxacin (CIP) adsorption from an aqueous solution. Although other studies have investigated chemical modification with various chemical agents, the novel use of oleic acid for modification yields unprecedented results in terms of CIP removal efficiency. Dependent parameters were optimized using the sample pH, contact interval, initial CIP concentration, and adsorbent dose. Using response surface methodology (RSM) with a central composite design (CCD), a dose of 0.3 g/100 mL produced excellent removal efficiency (above 81%) for CIP concentrations of 60 mg/L after 90 minutes of contact at pH 6. With an R2 (correlation coefficient) value of 0.985, analysis of variance (ANOVA) based on the CCD-RSM demonstrated a good fit between the experimental results and the predictions of the quadratic model. The Langmuir isotherm model was found to fit the CIP adsorption isotherms on the PPOA very well, with a theoretical maximum of 19.90 mg/g, indicating monolayer adsorption. Furthermore, a pseudo-second-order model could adequately describe the adsorption kinetics, implying that the adsorption rate is influenced by chemisorption. The main mechanisms underlying CIP biosorption are ion exchange and electrostatic attraction, whereas adsorption mechanics are controlled by external mass transfer and intra-particle diffusion. Thermodynamic analysis confirmed that adsorption was exothermic and spontaneous. After four consecutive repetitions, the adsorbent adsorption efficiency decreased from 81.88% to 50.91%, indicating its reusability. The results showed that pomegranate peel (PP) is an inexpensive adsorbent for CIP removal. Using this byproduct, CIP was effectively removed.
Per- and polyfluoroalkyl substances (PFAS) are persistent and toxic contaminants that are difficult to remove from complex wastewater because dissolved organic matter, salts, co-pollutants, and membrane fouling reduce treatment efficiency. This study evaluated an integrated adsorption-membrane process for PFAS removal through combined Aspen Plus/MATLAB simulation and bench-scale validation using synthetic complex wastewater. Adsorbent dosage (0.10-1.00 g/L), transmembrane pressure (4-10 bar), and filtration time were investigated. Standalone adsorption was limited by its reduced affinity for short-chain PFAS and by competitive uptake of co-existing dissolved organic matter, whereas standalone nanofiltration was constrained by progressive membrane fouling and flux decline; the integrated configuration was therefore designed to combine the strengths of both unit operations, using adsorptive pre-loading to lower the PFAS and organic load reaching the membrane so as to improve overall removal while mitigating fouling. Adsorption and nanofiltration achieved maximum total PFAS removals of 89.1% and 91.2%, respectively, while the integrated system reached 98.6% at 0.75 g/L PAC and 8 bar, with lower membrane flux decline (reduced from 33.5% to 21.8%) than NF-only operation. Model predictions showed good agreement with the experimental data (R² = 0.975-0.992), indicating that the integrated adsorption-membrane approach is a viable and scalable option for PFAS removal from complex wastewater.
Drilling operations in the Halfaya oilfield frequently encounter severe wellbore instability challenges. When navigating shale deposits, wellbore instability remains the primary operational concern. Based on the analysis of the wellbore instability intervals, low-strength shale and marlstone formations are identified as the principal unstable zones that lead to non-productive time and higher drilling costs. By planning a safe operating mud window, these non-productive times and drilling costs can be mitigated. Several wellbore instability concerns have been found in a southern Iraqi oil field. A problem-diagnostic technique was done by evaluating well log data, drilling reports, mud logging reports, and pore pressure readings. In wellbore stability evaluations, the three rock failure criteria that are used the majority of the time are the Mohr-Coulomb, Mogi-Coulomb and Modified Lade criterion were used to predict a safe mud weight window. The Mogi-Coulomb and Modified Lade criteria provided more accurate predictions than the Mohr-Coulomb model in well H1. The Mohr-Coulomb criterion proved inadequate for this formation because it fails to account for the intermediate principal stress. According to the pore pressure predictions in this study, the unsuitable mud weight of 10.49 ppg is the major cause of wellbore instability during the drilling of the Nahr Umr A formation in this well; therefore, a mud weight of 14.5–15 ppg is recommended. The Formation Micro Imager (FMI) was responsible for determining the orientations of the horizontal stresses. The Halfaya oilfield has an azimuth that corresponds to a maximum horizontal stress of about N20–35 E, the findings indicate that the Nahr Umr formation is characterized by a reversal faulting regime > > . Formation lithology impacts Halfaya oilfield horizontal stress. High-strength, hardened intervals have high horizontal stress, shale and marlstone formations with low strength are the principal unstable wellbore intervals. Ultimately, to prevent breakout failures and minimize drilling fluid losses, it is recommended to either restrict wellbore inclination or employ an optimized, higher mud weight.
Greenfield development planning is a challenging problem due to the complex objective function and the large number of variables. While stochastic algorithms and data-driven offline surrogate models have been used to locate and control wells, these methods often require a large number of runs or fail to reach an accurate optimal solution. For this reason, the current study aimed to develop a dynamic surrogate model updated after each evaluation, referred to as an active learning model. In this study, deepEnsemble and gaussian process (GP) algorithms were applied as an active alternative model. This approach was compared with optimization algorithms directly coupled with real simulations, where algorithms such as genetic algorithms (GA), particle swarm optimization (PSO), complex matrix adaptation evolution strategy (CMA-ES), and differential evolution (DE) were used for comparison. The deepEnsemble active model outperformed the other approaches, achieving a net present value (NPV) of more than 1 E+10 and 17% recovery factor (RF) for a field in southern Iraq for a production scenario. The algorithm suggested shutting in two existing wells and drilling 23 new wells. The algorithm was also tested using a water injection scenario; a stable pressure, NPV of approximately 1.28 E+10, and 25% RF was achieved by suggesting drilling 39 new wells, 17 of which were injection wells. The approach has proven effective in dealing with complex field development problems with a minimum number of runs.
With increasing population and development, the resources of fossil fuels decreased, leading to the need to find alternative sources of energy. Furthermore, the use of fossil fuels is accompanied by several downsides including environmental fatality associated with toxic gas emissions from diesel engines and continuous increase of the price of diesel fuel. Biodiesel is one of the most important types of renewable energy that replaces the fossil fuel requirement (mineral diesel) and maintains eco-friendly sustainability. Calcium is an essential plant nutrient as it plays an important role in the formation of plant cell walls and membranes. Therefore, the fallen leaves of mango tree can be utilized to produce nano calcium oxide and serve as a highly effective catalyst in the transesterification process for biodiesel production. The green approach of mango leaves extract is more cost-effective, nontoxic, and environmentally friendly compared to other ways such as chemical and physical procedures. Transesterification reaction was conducted at fixed parameters of 65 ℃ reaction temperature, 3 wt.% catalyst concentration, 1.5 h reaction time, and 50% alcohol to oil weight ratio. The effects of several other parameters on the transesterification reaction were studied such as the volume of the reaction mixture, mixing speed, FFA% content, and methanol/ethanol weight ratio. The study found that methanol is more effective than ethanol as alcohol in transesterification reaction, and the FFA% has a slight effect on the catalyst to 1.8% FFA. The produced biodiesel was characterized by GC-MS and FT-IR analysis which indicate the presence of esters. The physical and fuel characteristics of the produced biodiesel were measured; it had a viscosity of 3.708 mm2/s, a density of 0.88869 g/cm3, and a flash point of 108 °C.
The induced electrochemical-Fenton (I-EF) process is one of the electrochemical advanced oxidation processes (EAOPs) that has been recently applied to treat various types of wastewaters. In this work, the I-EF process, comprising a graphite/SnO2-Sb2O3 anode, an iron-screen-induced electrode, and an air-diffusion cathode, was used to treat petroleum refinery wastewater. The effects of current density (2-10 mA/cm²), pH (3-7), and the number of screens on the induced electrode (1 and 4) on chemical oxygen demand (COD) removal were investigated. Results showed that increasing pH improved COD removal, whereas increasing current density beyond 3 mA/cm2 reduced it. Increasing the screen number also enhanced the COD removal. The preferred conditions were a current density of 3 mA/cm², pH of 7, and four screens, resulting in a COD removal of 88% within 120 min, which claimed an electrical energy consumption of 0.8575 kWh/m³, confirming the successful application of I-EF in petroleum refinery wastewater treatment under natural pH with minimum sludge generation.
The green synthesis of nanoparticles and activated carbon has attracted researchers' interest due to its rapid, cost-effective, sustainable, and environmentally friendly nature. In this paper, the synthesis of activated carbon (AC) and nickel oxide nanoparticles (NiO-NPs) from Ficus carica leaf and their extracts for the removal of malachite green from aqueous solutions. activated carbon (AC) was synthesized from Ficus carica leaves using a pyro-carbonic acid microwave method. In contrast, nickel oxide nanoparticles were produced using leaf extracts as a reducing and stabilizing agent. The manufactured activated carbon and NiO nanoparticles were characterized by Brunauer-Emmett-Teller analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The influence of various factors, including malachite green concentration, pH, contact time, and dosages of NiO, AC, and NiO/AC, was examined using Response Surface Methodology (RSM) in Design-Expert (13 Stat-Ease). the optimal parameters for achieving maximum removal efficiency of malachite green dye were determined to be an initial concentration of 150 mg/L, pH of 4, a contact period of 120 minutes, and an adsorbent dosage of 0.25 g/L, resulting in removal efficiencies of 97.9202%, 98.8932%, and 99.9776%, respectively. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, and pseudo-first- and second-order kinetic models. the results indicated that the Freundlich isotherm and pseudo-second-order kinetic models were the most effective in representing the equilibrium adsorption data.
The region of Kirkuk and its surrounding areas, including (Baba, Jambour, Qara Chuq, Qaiyarah, Demir Dagh, Bai Hassan, Taq Taq, Makhul, Gilabat as well as southern Mosul and the cities of Erbil and Sulymania, are known as one of the oldest discovered oil fields in northern Iraq. This area presents a significant opportunity for further organic geochemical analysis to describe maturation zones and estimate economically generated hydrocarbons with particular reference to the Sargelu formation, to enhance hydrocarbons productivity. To assess the potential of these oil fields, it is essential to perform correlation, comparisons, and geochemical analyses of the data collected from exploration wells in the surrounding area. This approach provides key information and evidence related to the source rock precursors, maturation indices, and other physical properties. The depth of samples in this study ranges from 5,125 ft (1,562 m) to 10,866 ft (3,312 m). Notably, about 20% of these samples demonstrate Total Organic Carbon (TOC) values higher than 4%, with Rock-Eval Hydrogen indices (HI) between 100 and 600, corresponding to Tmax values within the oil generative window. The proven TOC value that has been measured is 16%, while the recorded HI value is 442, and the Tmax value of 439°C. The oil and gas accumulations of the Cretaceous and Tertiary in the Mesopotamian Basin and Zagros fold belt are overlying mature Jurassic source rocks, emphasizing the importance of vertical migrat ion in hydrocarbon generation. Terpane and Sterane biomarker distributions as well as stable carbon isotope values were determined for oils in the region and potential Sargelu source rock extracts in order to determine dependable oil-to-source rock correlations. The remarkable API gravity, sulfur content, and biomarker ratio provide valuable insights into the source and maturity of various reservoirs. The high sulfur content and wide range of API gravity, from extra heavy to light, are achieved within the range of 8.5–43.3 API.
Oxidative desulfurization (ODS) has attracted interest in the academic and industrial fields to meet new, stringent environmental legislation and produce environmentally friendly fuel. In this work, catalytic oxidative desulfurization of dibenzothiophene (DBT) compounds in diesel fuel is studied using a co-magnetic active oxide over an activated carbon (Fe2O3 + MnO2/AC) catalyst. DBT oxidation reactions are conducted in new oscillatory and non-oscillatory baffled reactors (OBR and NOBR). New central baffles for handling catalyst particles as a fixed bed in the OBR are developed for the first time. ODS process is examined using hydrogen peroxide as oxidant under different operating parameters: temperatures: 30 - 90 °C, oxidation times: 3–12 min, frequency: 0.5 - 2 Hz, and amplitude: 3 -12 mm. The results observed that the highest desulfurization efficiency (98.1 %) is achieved under the best conditions (90 °C, 12 min, 2 Hz, and 12 mm) in OBR. The dramatic DBT oxidation in a short desulfurization time is mainly attributed to the synergistic effect of oscillatory flow and the high activity of the synthesized catalyst. The desulfurization kinetic model is examined under the best conditions. Kinetic results show that ODS reactions follow a first-order model. Also, a low activation energy (3.68 kJ/mol) is determined, which proves rapid DBT oxidation at a lower required energy.
The kinetic study of the visible-light-driven photocatalytic degradation of methylene blue (MB) dye by the Ag₂O@CRA heterojunction photocatalyst and robust polyvinylidene fluoride membranes incorporating Ag₂O@CRA heterojunction photocatalyst (PVDF/Ag₂O@CRA) was investigated. This study involves a comparison of the outcomes of the kinetic study performed based on the experimental data of the oxidative photocatalytic degradation of the MB dye. The zero-order, pseudo-first-order, and modified Freundlich kinetic models were applied to accomplish this study. The results showed that the photocatalytic oxidation of the MB dye by the Ag2O@CRA photocatalyst followed the pseudo-first-order kinetic model, and the apparent rate constant (k1) value was 0.1231 min-1. The photocatalytic oxidation of the MB dye by the modified PVDF membrane with 0.3 wt.% Ag2O@CRA photocatalyst followed the pseudo-first-order kinetic model, and the apparent rate constant (k1) value was 0.0196 min-1. Also, the Langmuir-Hinshelwood model was used to model the MB photocatalytic degradation kinetics by the Ag2O@CRA photocatalyst for 10-40 mg/L inlet MB concentrations. Likewise, the Langmuir-Hinshelwood model was used to model the kinetics of the MB photocatalytic degradation by the PVDF membrane with 0.3 wt.% Ag₂O@CRA photocatalyst for 5-20 mg/L inlet MB concentrations. It was found that the intrinsic photocatalysis reaction rate constant (kr) was 0.8286 mg/L.min for the Ag₂O@CRA heterojunction photocatalyst and 0.209 mg/L.min for the PVDF/Ag₂O@CRA photocatalytic membrane. Also, it was found that the equilibrium adsorption constant (Kad.) was 0.3245 L/mg for the Ag₂O@CRA heterojunction photocatalyst and 0.218 L/mg for the PVDF/Ag₂O@CRA photocatalytic membrane. The manufacturing cost for the Ag₂O@CRA photocatalyst and PVDF/Ag₂O@CRA photocatalytic membrane was estimated to be $2.45/10 g and $78/m², respectively.
Airlift bioreactors have been classified as a promising technology for microalgae cultivation. Several improvements have contributed to increasing the mixing efficiency and production. However, some challenges are still facing this biological process. One challenge is the efficient dissolution and delivery of carbon dioxide to microalgae cells, which remains a limiting factor in the biological processes. On the other hand, sparging the gas in large quantities may lead to gas loss if microorganisms do not completely consume it. In this study, microalgae were cultivated in two stages and compared: the first stage of injecting 5 ml of carbon solution into a conical flask and the second stage of sparging 5 liters/hour in an airlift bioreactor with increasing sparging time this is done by sparging carbon dioxide gas at the same flow rate from day to day, but increasing the sparging time by 30 seconds, starting with sparging the gas for one minute until reaching 7 minutes. The results showed that the airlift bioreactor gives a higher growth rate of microalgae than that produced in a conical flask. The maximum biomass concentration reached 5 g/L in the airlift bioreactor culture with a maximum specific growth rate of 0.324 day−1, while it reached 1.0799 g/L in the conical flask culture with a specific growth rate of 0.187 day−1. This result shows the importance of the airlift bioreactor in microalgae cultivation. Also, the internal composition of the biomass was found that the airlift bioreactor was the best, as the amount of lipids, carbohydrates and protein was (2.06, 1.43, and 18.03 g per 30 g of dry biomass), respectively, while the internal composition of the control cultivation was (0.005386, 0.00428, 0.05754 and g/L), respectively. The volumetric mass transfer coefficient showed that when the sparging time increases, the oxygen gas transfer coefficient increases until it reaches 1.0397 s−1. The pH value was also maintained around 7, which is the appropriate value for increasing the growth rate.
