Flat Plate Reactor Research Articles

Multiphysics fields simulation of photothermal catalytic degradation of R134a in a flat plate reactor

Photothermal catalytic degradation is an environment-friendly way to dispose high-global-warming-potential hydrofluorocarbon refrigerants (HFCs). There are challenges in understanding the heat and mass transfer mechanism of this multi-physicochemical process. This study focuses on photothermal catalytic degradation of R134a, one of the hydrofluorocarbon refrigerant, in a flat plate reactor. A numerical model was developed to couple laminar flow, conjugate heat transfer, dilute species transport, surface radiation and chemical reaction. Meanwhile, experiments were conducted to measure the R134a degradation across various temperatures. The parameters of thermal boundary conditions and the kinetics were calibrated by combining the experimental data and the numerical model. The preexponential factor of 0.1146 m/s and activation energy of 21129.1 J/mol were yielded, achieving less than 10 % relative error of the R134a concentration. The average degradation rate was intensified by around one magnitude from 100 °C to 400 °C. Across various temperatures, molecular diffusion always dominated the mass transport process. However, the governing mechanism limiting the photothermal catalytic process was the degradation kinetics, as evidenced by the uniform concentration distribution and the Damköehler number significantly below 1. Several methods were also proposed to enhance the photothermal catalytic degradation rate.

Continuous Flow Hydroxylation of Benzene to Phenol in a Photocatalytic Millistructured Flat-Plate Reactor

Continuous Flow Hydroxylation of Benzene to Phenol in a Photocatalytic Millistructured Flat-Plate Reactor

Strong electron coupling effect of non-precious metal Schottky junctions enhanced square meter level photocatalytic hydrogen evolution

Photocatalytic hydrogen production technology utilizes solar energy to decompose water into hydrogen, helping to alleviate the pressure of energy depletion. Engineering of non-precious metal nanomaterials as cocatalysts can play a significant role in low-cost, sustainable, and large-scale photocatalytic hydrogen production. Herein, MnCdS-Vs/NiCo2S4 (MCSN) Schottky junction nanomaterials with strong electron coupling effect were prepared by a two-step hydrothermal method and successfully applied to a square meter hydrogen evolution device. The optimized MCSN material demonstrated high hydrogen evolution activity of 34.28 mmol g−1 h−1, which is 9.34 and 685.60 times higher than that of pure MnCdS-Vs and NiCo2S4, respectively. More importantly, in a square meter (1 m2) flat-plate reactor, MCSN produced H2 evolution approximately 201 mmol in 5 h, showcasing its potential for large-scale applications. In-situ XPS and DFT calculations demonstrated that MnCdS-Vs interacts with NiCo2S4 to produce a strong electron coupling effect and form a Schottky junction. It promotes the facilitated the directional migration of photogenerated electrons from MnCdS-Vs to NiCo2S4, but also effectively suppressed electron backflow through the Schottky barrier. Furthermore, the abundance of sulfur vacancies enhanced visible light absorption capability, further improving photocatalytic hydrogen evolution performance. This work delves into the role of defect engineering and Schottky junction design in enhancing photocatalytic performance, providing new insights into transitioning photocatalytic hydrogen production technologies from small-scale laboratory experiments to large-scale practical applications.

Performance enhancement of desorption reactor in the electrochemically mediated amine regeneration CO2 capture process: Thru modelling, simulation, and optimization

The electrochemically mediated amine regeneration (EMAR) carbon dioxide (CO2) capture process has significant potential in mitigating CO2 emissions. A suitable desorption reactor plays a pivotal role in realizing the efficient utilization of the EMAR technology. This study concentrates on the simulation and improvement of the desorption reactor for the EMAR process. To begin with, a comprehensive multi-physics model was developed to simulate the desorption process within a laboratory flat-plate reactor. The concentration distributions of reactive ions and the effect of CO2 bubbles in the electrolyte were analyzed. Results indicated that shortening electrode length is a practical measure to enhance desorption reactor efficiency. The study also explored the impact of critical operational variables, including electrolyte flow direction, flow rate, copper ions loading, and applied potential. Notably, controlling the applied potential proved highly effective for regulating desorption performance, with optimal adjustment maximizing overall efficiency. Based on these findings and the characteristics of the EMAR process, a novel multi-electrode partitioned EMAR desorption reactor was proposed as an enhancement to the flat-plate reactor. By applying distributed potential, improved desorption performance was obtained, resulting in a 20.05% increase in the CO2 desorption rate with only a 4.04% increase in the unit desorption energy consumption. These findings provide significant insights for optimizing the design and implementation of the EMAR desorption reactor.

Influence of visible light LEDs modulation techniques on photocatalytic degradation of ceftriaxone in a flat plate reactor

In this paper, the effect of light modulation on photocatalytic ceftriaxone (CEF) degradation in aqueous solution was investigated. The experimental set-up consisted of a fixed bed photocatalytic reactor with a flat plate geometry and visible LEDs for irradiation. Fe-N-codoped TiO2 photocatalyst was immobilized on a polystyrene plate (PS) by solvent casting method to achieve a structured photocatalyst (Fe-N-TiO2/PS), which was loaded in the photoreactor. Raman and UV–Vis diffuse reflectance spectroscopy confirmed the presence of Fe-N-TiO2 on the PS surface and its uniform distribution on the polymer support. Various LEDs dimming techniques were tested with fixed and variable duty-cycle values. In particular, the following modulations were used: fixed duty-cycle (FD), sinusoidal variable duty-cycle (S-VD), triangular variable duty-cycle (T-VD), square wave variable duty-cycle (SW-VD), saw-tooth variable duty-cycle (ST-VD), pulse variable duty-cycle (P-VD), and pseudo-sinusoidal variable duty-cycle (PS-VD). The optimal light modulation was the S-VD, with an average fed current between 25 and 75 mA and a period of 30 s. Indeed, by using S-VD modulation, the highest value of the apparent CEF degradation kinetic constant (resulting 0.0082 min−1) and the highest total organic carbon (TOC) removal (70 %) were achieved. By comparing the electric energy consumption (EE/O) with S-VD modulation used in this work with those found in other literature studies dealing with the photocatalytic ceftriaxone degradation, a significant decrease of EE/O was evidenced. Moreover, toxicity test showed that the photocatalytic treatment allowed to significantly reduce the toxicity of CEF solution when compared to untreated effluent.

A novel hybrid continuous-flow wastewater treatment for lamotrigine degradation by combining enzymatic and photo-oxidative reactions

In response to the increasing occurrence of lamotrigine (LMG) in wastewater, low removal efficiency of conventional treatments, and the need for advanced and innovative approaches, our work aimed to develop and optimize a hybrid enzymatic-photo-oxidative treatment. The coupling of immobilized homemade peroxidase and UVC/H2O2 was first studied in batch mode. The hybrid reactions resulted in 100 % removal and a first-order specific reaction rate of 0.142 min−1 at 80 mg L−1 of H2O2. Subsequently, our research focused on treatment optimization in a flat-plate reactor operated in continuous flow. Response surface methodology revealed that maintaining a UVC dose of 3240 mJ cm−2 allows >90 % removal across a wide range of H2O2 concentrations. The experiment with LMG-spiked effluent confirmed the effectiveness of the proposed treatment for removing the antiepileptic from a real matrix. The proposed degradation pathway shows that the system can oxidize lamotrigine by sequential reactions with additional dechlorination steps not yet reported. Furthermore, only the hybrid reactions showed environmental safety, as confirmed by cytotoxicity studies. Notably, our study evaluated, for the first time, the coupling of enzymatic and photo-oxidative reactions in a single reactor operated in continuous-flow mode. The operational flexibility suggests its potential application for wastewater treatment facilities.

Solar photocatalysis application in UWWTP outlets - simulations based on predictive models in flat-plate reactors and pollutant degradation studies with in silico toxicity assessment

The application of the solar photocatalysis for the degradation of residual pollutants found in surface water was demonstrated. Semi-pilot scale flat-plate cascade reactor (FPCR) was used to study the degradation of model organic pollutants: enrofloxacin (ENRO), 17β-estradiol (E2) and 1H-benzotriazole (1H-BT) over TiO2 thin-film supported on glass fibers. A modular panel with full-spectra solar lamps with appropriate UVB and UVA irradiation levels was used as a simulation of sunlight. Pollutant degradation in FPCR was estimated using predictive models; intrinsic reaction rate constants (ki) for ENRO, E2 and 1H-BT independent of the reactor size, flow rate and irradiation conditions were determined: 9.60, 3.35 and 0.37 109 s−1 W−0.5 m1.5, respectively. Main degradation products (DPs), formed upon hydroxylation, ring opening and oxidation, were identified using LC-QTOF-MS. The ecotoxicological impact was assessed via T.E.S.T. and ECOSAR open-source tools showing the formation of less harmful DPs after sufficient reaction time. Pollutant degradation was simulated at four locations of interest, i.e. exhausts from urban wastewater treatment plants (UWWTPs) in Zagreb, Croatia (45°N), Krakow, Poland (50°N), Sevilla, Spain (37°N) and Ioannina, Greece (39.6°N). Results have proved that a simple flat-plate system with supported photocatalysts can be easily scaled up and incorporated at the outlet of UWWTP for the reduction of pollutant load and related toxicity. The exhaust canal in Zagreb with the estimated length of a photocatalytic layer of 122 m for the > 90% degradation of all target pollutants was discussed as the best installation site among studied locations. Environmental ImplicationA multi-disciplinary approach to the tentative application of TiO2 solar photocatalysis outdoors to reduce pollutant loads and toxicity in surface waters was demonstrated. Possible application at four selected locations in Europe, as an additional step in water treatment after urban wastewater treatment plants (UWWTPs) was discussed. Target pollutants were studied under environmentally relevant conditions (sunlight levels, water matrix, simulation of process on a real scale at selected geographical location), at both higher and low concentrations.

Amoxicillin Degradation by TiO2 P25 Solar Heterogeneous Photocatalysis: Influence of pH and Oxidizing Agent H2O2 Addition

Over the years, there has been an increase in the consumption of drugs, particularly antibiotics. Amoxicillin (AMX) is considered one of the most widely used antibiotics, causing resistance in microorganisms in the ecosystem where it is found. Additionally, it has been cataloged among the drugs under surveillance by the European Commission since 2020. The present work studies the efficiency of AMX degradation by photolysis and heterogeneous solar photocatalysis processes under different reaction pH levels (3.5, 4.15, 7 and 9) and observing the influence of different doses of H2O2 (nil and 4 mM), as an oxidizing agent. TiO2 P25 was used as photocatalyst, impregnated in glass supports of 0.1 and 1 m2 in flat plate reactors (FPR). A 2 × 2 × 4 statistical analysis carried out after repeated measurements to determine the relationship between the different parameters involved (process, H2O2 dose, and pH). The kinetics of the AMX degradation reaction showed the best rate constant (KphC = 0.10 min−1) under acidic medium conditions (pH 4.15), without addition of H2O2, and by heterogeneous photocatalysis when using a 1 m2 FPR to achieve 100% COD removal. ANCOVA showed significant differences (p < 0.05) in the use of H2O2 for the first minutes of the reaction and in the different FPR surfaces.

Long-Term Stable Hydrogen Production from Water and Lactic Acid via Visible-Light-Driven Photocatalysis in a Porous Microreactor.

Photocatalytic hydrogen (H2) production is significant to overcome challenges like fossil fuel depletion and carbon dioxide emission, but its efficiency is still far below commercialization need. Herein we achieve long-term stable H2 bubbling production from water (H2O) and lactic acid via visible-light-driven photocatalysis in a porous microreactor (PP12) benefit for photocatalyst dispersion, charge separation, mass transfer and dissociation of O-H bonds of H2O. With the widely used platinum/cadmium-sulfide (Pt/CdS) as photocatalyst, PP12 leads to a H2 bubbling production rate of 602.5 mmol h-1 m-2, which is 1000 times higher than that in traditional reactor. Even when amplifying PP12 into a flat-plate reactor with an area as large as 1 m2 and elongating reaction time to 100 h, H2 bubbling production rate still remains at around 600.0 mmol h-1 m-2, offering a great potential for commercialization.

Efficient adsorptive removal of diclofenac sodium by acidified MIL101(Cr): optimizing the content of phosphotungstic acid, flow loop thin film slurry flat plate reactor

Efficient adsorptive removal of diclofenac sodium by acidified MIL101(Cr): optimizing the content of phosphotungstic acid, flow loop thin film slurry flat plate reactor

Expanding mechanistic models to represent purple phototrophic bacteria enriched cultures growing outdoors

The economic feasibility of purple phototrophic bacteria (PPB) for resource recovery relies on using enriched-mixed cultures and sunlight. This work presents an extended Photo-Anaerobic Model (ePAnM), considering: (i) the diverse metabolic capabilities of PPB, (ii) microbial clades interacting with PPB, and (iii) varying environmental conditions. Key kinetic and stoichiometric parameters were either determined experimentally (with dedicated tests), calculated, or gathered from literature. The model was calibrated and validated using different datasets from an outdoors demonstration-scale reactor, as well as results from aerobic and anaerobic batch tests. The ePAnM was able to predict the concentrations of key compounds/components (e.g., COD, volatile fatty acids, and nutrients), as well as microbial communities (with anaerobic systems dominated by fermenters and PPB). The results underlined the importance of considering other microbial clades and varying environmental conditions. The model predicted a minimum hydraulic retention time of 0.5 d−1. A maximum width of 10 cm in flat plate reactors should not be exceeded. Simulations showed the potential of a combined day-anaerobic/night-aerobic operational strategy to allow efficient continuous operation.

Arsenite to Arsenate Oxidation and Water Disinfection via Solar Heterogeneous Photocatalysis: A Kinetic and Statistical Approach

Arsenic (As) poses a threat to human health. In 2014, more than 200 million people faced arsenic exposure through drinking water, as estimated by the World Health Organization. Additionally, it is estimated that drinking water with proper microbiological quality is unavailable for more than 1 billion people. The present work analyzed a solar heterogeneous photocatalytic (HP) process for arsenite (AsIII) oxidation and coliform disinfection from a real groundwater matrix employing two reactors, a flat plate reactor (FPR) and a compound parabolic collector (CPC), with and without added hydrogen peroxide (H2O2). The pseudo first-order reaction model fitted well to the As oxidation data. The treatments FPR–HP + H2O2 and CPC–HP + H2O2 yielded the best oxidation rates, which were over 90%. These treatments also exhibited the highest reaction rate constants, 6.7 × 10−3 min−1 and 6.8 × 10−3 min−1, respectively. The arsenic removal rates via chemical precipitation reached 98.6% and 98.7% for these treatments. Additionally, no coliforms were detected at the end of the process. The collector area per order (ACO) for HP treatments was on average 75% more efficient than photooxidation (PO) treatments. The effects of the process independent variables, H2O2 addition, and light irradiation were statistically significant for the AsIII oxidation reaction rate (p < 0.05).

Comparative Efficiencies for Phenol Degradation on Solar Heterogeneous Photocatalytic Reactors: Flat Plate and Compound Parabolic Collector

Phenol is a recalcitrant anthropogenic compound whose presence has been reported in both wastewater and drinking water; human exposure to phenolic substances can lead to health problems. The degradation of phenol (measured as COD decrease) through solar heterogeneous photocatalysis with immobilized TiO2 was performed in two different reactors: a flat-plate reactor (FPR) and a compound parabolic collector (CPC). A 23 full factorial experimental design was followed. The variables were the presence of TiO2, H2O2 addition, and the type of reactor. Data were fitted to the pseudo-first-order reaction-rate-kinetics model. The rate constant for photocatalytic phenol degradation with 1 mM of H2O2 was 6.6 × 10−3 min−1 for the FPR and 5.9 × 10−3 min−1 in the CPC. The calculated figures of merit were analyzed with a MANCOVA, with UV fluence as a covariate. An ANCOVA showed that the type of reactor, H2O2 addition, or fluence had no statistically significant effect on the results, but there was for the presence of TiO2. According to the MANCOVA, fluence and TiO2 presence were significant (p < 0.05). The CPC was on average 17.4% more efficient than the FPR when it came to collector area per order (ACO) by heterogeneous photocatalysis and 1 mM H2O2 addition.

Light attenuation in enriched purple phototrophic bacteria cultures: Implications for modelling and reactor design

Light attenuation in enriched purple phototrophic bacteria (PPB) cultures has not been studied, and its understanding is critical for proper process modelling and reactor design, especially for scaled systems. This work evaluated the effect of different biomass concentrations, reactor configurations, wastewater matrices, and growth conditions, on the attenuation extent of near infra-red (NIR) and ultraviolet-visible (UV–VIS) light spectra. The results show that increased biomass concentrations lead to higher light attenuation, and that PPB absorb both VIS and NIR wavelengths, with both fractions of the spectrum being equally absorbed at biomass concentrations above 1,000 g COD·m−3. A flat plate configuration showed less attenuation compared with cylindrical reactors illuminated from the top, representative for open ponds. Neither a complex wastewater matrix nor the presence of polyhydroxyalkanoates (under nutrient limited conditions) affected light attenuation significantly. The pigment concentration (both bacteriochlorophyll and carotenoids) however, had a strong effect, with significant attenuation in the presence of pigments. Attenuation predictions using the Lambert-Beer law (excluding scattering) and the Schuster model (including scattering) indicated that light scattering had a minimal effect. A proposed mathematical model, based on the Lambert-Beer law and a Monod function for light requirements, allowed effective prediction of the kinetics of photoheterotrophic growth. This resulted in a half saturation coefficient of 4.6 W·m−2. Finally, the results showed that in dense outdoor PPB cultures (≥1,000 g COD·m−3), effective light penetration is only 5 cm, which biases design away from horizontal lagoons, and towards non-incident multi-panel systems such as flat plate reactors.

Naturally illuminated photobioreactors for resource recovery from piggery and chicken-processing wastewaters utilising purple phototrophic bacteria

Resource recovery from wastewater, preferably as high value products, has become an integral part of modern wastewater treatment. This work presents the potential to produce single cell protein (SCP) from pre-settled piggery wastewater (PWW) and meat chicken processing wastewater (CWW), utilising anaerobic purple phototrophic bacteria (PPB). PPB were grown as biofilm in outdoors 60 L, 80 L and 100 L flat-plate reactors, operated in sequential batch mode. PPB biofilm was recovered from reactor walls at a total solid (TS) content ∼90 g•L − 1, and the harvested biomass (depending on the wastewater) had a consistent quality, with high protein contents (50–65%) and low ash, potentially applicable as SCP. The COD, N and P removal efficiencies were 71±5.3%, 22±6.6%, 65±5.6% for PWW and 78±1.8%, 67±2.7% and 37±4.0% for CWW, respectively, with biofilm areal productivities up to 14 g TS•m − 2•d − 1. This was achieved at ammonium-N concentrations over 1.0 g•L − 1 and temperatures up to 55 °C and down to 6 °C (daily fluctuations of 20–30 °C). The removal performances and biomass productivities were mostly dependent on the bioavailable COD in the form of volatile fatty acids (VFA). At sufficient VFA availability, the irradiance became limiting, capping biofilm formation. Harvesting of the suspended fraction resulted in increased productivities and recovery efficiencies, but lowered the product quality (e.g., containing undesired inerts). The optimum between quantity and quality of product is dependent on the wastewater characteristics (i.e., organic degradable fraction) and potential pre-treatment. This study shows the potential to utilise sunlight to treat agri-industrial wastewaters while generating protein-rich PPB biomass to be used as a feed, feed additive or feed supplement.

Solar Heterogenous Photocatalytic Degradation of Methylthionine Chloride on a Flat Plate Reactor: Effect of pH and H2O2 Addition

Methylthionine chloride (MTC) is a compound with several applications both in the clinical and medical industries. Nevertheless, such compounds can become an environmental problem, as they are not properly treated by wastewater treatment plants. This objective of this work was to study MTC degradation in a flat plate reactor through solar photolysis and heterogeneous photocatalysis processes with TiO2 as a catalyst. In addition to the processes, three pH (3.5, 6.5, and 9) and the effect of H2O2 addition (no dose, 0.5, and 1 mM/L) were tested. The results show that acidic pH is the most appropriate for MTC degradation, which ranged between 56% and 68.7% for photolysis and between 76% and 86.7% in photocatalysis. The H2O2 addition resulted in lower degradation in all cases, leading the authors to conclude that the presence of peroxide actually hinders degradation in solar photolysis and photocatalysis processes. Statistical analysis showed that the constant rate reactions calculated for every process, under the same conditions of pH and H2O2 addition, are significantly different from one another, and the three factors considered for experimental design (process, pH, and H2O2) have a statistically significant effect on MTC degradation. The collector area per order confirmed higher efficiency for photocatalysis when compared to photolysis processes.

Suitability of Different Titanium Dioxide Nanotube Morphologies for Photocatalytic Water Treatment.

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO2) has been used extensively for this purpose. Anodic oxidation allows for the synthesis of a highly ordered nanotubular structure with a high degree of tunability. In this study, a series of TiO2 arrays were synthesised using different electrolytes and different potentials. Mixed anatase-rutile photocatalysts with excellent wettability were achieved with all the experimental iterations. Under UVA light, all the materials showed significant photoactivity towards different organic pollutants. The nanotubes synthesised in the ethylene glycol-based electrolyte exhibited the best performance, with near complete degradation of all the pollutants. The antibacterial activity of this same material was similarly high, with extremely low bacterial survival rates. Increasing the voltage resulted in wider and longer nanotubes, characteristics which increase the level of photocatalytic activity. The ease of synthesis coupled with the excellent activity makes this a viable material that can be used in flat-plate reactors and that is suitable for photocatalytic water treatment.

Reaction kinetics formulation with explicit radiation absorption effects of the photo-Fenton degradation of paracetamol under natural pH conditions.

The degradation of paracetamol (PCT) in an aqueous medium using the Fenton and photo-Fenton reactions was investigated. The aim of this research was the development of a kinetic model based on a reaction mechanism, which includes two main intermediates of PCT degradation and the local volumetric rate of photon absorption (LVRPA). Ferrioxalate was used as a catalyst and the working pH was adjusted to 5.5 (natural pH). Experimental work was planned through a D-optimal experimental design and performed in a flat plate reactor irradiated by a solar simulator. Hydrogen peroxide (HP) concentration, reaction temperature, and radiation level were the operating parameters. The photo-Fenton reaction allowed to reach a minimum relative PCT concentration of 2.01% compared to 5.04% achieved with Fenton reaction. Moreover, the photo-Fenton system required a 50% shorter reaction time and lower HP concentration than in dark conditions (90 min and 189 mg L-1 vs. 180 min and 334 mg L-1, respectively). The experimental results were used to estimate the kinetic parameters of the proposed kinetic model employing a nonlinear, multi-parameter regression method. The values obtained from the normalized root-mean-square error (14.52, 1.96, 4.36, 13.16, and 8.72 % for PCT, benzoquinone, hydroquinone, HP, and oxalate, respectively) showed a good agreement between the predicted and experimental data.

Photocatalytic degradation of the acetaminophen by nanocrystal-engineered TiO2 thin film in batch and continuous system

Un-biodegradable pharmaceuticals are one of the major growing threats in the wastewaters. In the current study, TiO2 thin film photocatalysts were designed by nanocrystal engineering and fabricated for degradation of the acetaminophen (ACE) in a photocatalytic reaction under UV light irradiation in batch and continuous systems. The photocatalyst was prepared by sputtering and then engineered by thermal treatment (annealing at 300°C (T300) and 650°C (T650)). The annealing effects on the crystallinity and photocatalytic activity of the TiO2 film were completely studied; it was found that annealing at higher temperatures increases the surface roughness and grain size which are favorable for photocatalytic activity due to the reduction in the recombination rate of photo-generated electron-hole pairs. For the continuous system, a flat plate reactor (FPR) was designed and manufactured. The photocatalytic performance was decreased with the increase of flow rate because the higher flow rate caused to form the thicker film of the liquid in the reactor and reduced the UV light received by photocatalyst. The reusability and durability of the samples after 6 h of photocatalytic reaction showed promising performance for the T650 sample (annealed samples in higher temperatures).

Carbon speciation and flocculation in Neochloris oleoabundans cultures using anaerobically digested stillage.

The effects of bicarbonate loading rate (BLR) and pH on growth kinetics, inorganic carbon speciation, carbon fixation and lipid content in Neochloris oleoabundans cultures using anaerobically digested stillage (ADS) (2% v/v) were investigated. Four different cultures were established: culture A with BLR = 1g l-1 day-1 and no pH adjustment, culture B with BLR = 0.5g l-1 day-1 and no pH adjustment, culture C with BLR = 1g l-1 day-1 and pH adjustment at 7.0, and culture D with BLR = 0.5g l-1 day-1 and pH adjustment at 7.0. The experiments were carried out in flat plate reactors (4l) at controlled conditions (light intensity of 134µmol photon m-1s-1 and photoperiod 16 light/8 darkness; temperature of 32 ± 1°C). The effects of pH (7, 10.41, 10.65, and 12), time (15, 30, 60, and 90min), and concentration of a cationic polyelectrolyte (CP) (10 and 20mg l-1) on the flocculation efficiency (FE) of N. oleoabundans were also investigated. The results showed that bicarbonate was the predominant carbon species in the media and the main carbon source for microalgae growth in all cultures. The highest productivity (87.70 ± 9.70mg l-1 day-1) and CO2(aq) fixation rate (0.15g CO2(aq) l-1 day-1) were found in culture B. The lipid content in N. oleoabundans was affected negatively by the pH adjustment at 7.0 during its growth; higher values were found in cultures with no pH adjustment (37.10% and 38.85% dw for culture A and B, respectively) as compared to those obtained in cultures with pH adjustment (27.35% and 22.20% dw for culture C and D, respectively) (p < 0.05). Regarding flocculation, the addition of 20mg CP l-1 was required to obtain a FE > 95% in cultures A and B, although a significant FE (40-59%) occurred without CP addition at a high pH (≥ 10.41) in all cultures.