Tubular Reactor Research Articles

Ca2Fe2O5-Based WGS Catalysts to Enhance the H2 Yield of Producer Gases

Ca2Fe2O5-based catalysts were synthesized from siderite and calcite precursors, which were processed in the form of pelletized samples and tested as water gas shift catalysts. Catalytic tests were performed in a tubular reactor, at temperatures in the range 400–500 °C and with different H2O:CO ratios, diluted with N2; this demonstrates the positive impact of Ca2Fe2O5 on conversion of CO and H2 yield, relative to corresponding tests without catalyst. The catalytic performance was also remarkably boosted in a microwave-heated reactor, relative to conventional electric heating. Post-mortem analysis of spent catalysts showed significant XRD reflections of spinel phases (Fe3O4 and CaFe2O4), and SiO2 from the siderite precursor. Traces of calcium carbonate were also identified, and FTIR analysis revealed relevant bands ascribed to calcium carbonate and adsorbed CO2. Thermodynamic modelling was performed to assess the redox tolerance of Ca2Fe2O5-based catalysts in conditions expected for gasification of biomass and thermochemical conditions at somewhat lower temperatures (≤500 °C), as a guideline for suitable conditions for water gas shift. This modelling, combined with the results of catalytic tests and post-mortem analysis of spent catalysts, indicated that the O2 and CO2 storage ability of Ca2Fe2O5 contributes to its catalytic activity, suggesting prospects to enhance the H2 content of producer gases by water gas shift.

Lab-scale tubular LED UV reactor for continuous photocatalysis

Photocatalytic water treatment is considered a promising technique to prevent micropollutants from entering the environment. However, no off-the-shelf UV reactors on lab scale are available to study new processes and photocatalysts. In this study, we present a tubular UV reactor equipped with 30 UV-LEDs, emitting UV light at 367 nm and a total radiant flux of 42W. The UV reactor has an irradiated length of 300 mm and can host any transparent chemical reactor on the inside with a maximum diameter of 28 mm. The device is optimized for lab experiments with total dimensions of just 334 mm x 193 mm x 172 mm. Besides water treatment, a broad range of other photochemical and photocatalytic experiments can be performed with the reactor. Two identical UV reactors have been built and are successfully used for photocatalytic water treatment experiments. The degradation of methylene blue with TiO2 as photocatalyst was studied to validate the UV reactor. Furthermore, photocatalytic and hybrid processes were conducted in the UV reactor to degrade a broad range of pharmaceutical micropollutants.

Determination of steady states of tank and recycle tubular reactors using homotopy and parametric continuation methods

Abstract This work concerns the application of the homotopy method to solve the mathematical model of a non-adiabatic chemical continuous stirred tank reactor (CSTR) and tubular reactor with mass recycle (TRR) (Berezowski 2000. Spatio-temporal chaos in tubular chemical reactors with the recycle of mass, Chaos, Solitons & Fractals, vol. 11, no. 8, pp. 1197–1204). This method was associated with the parametric multivariable continuation algorithm. Thanks to this, this method can automatically find all the multiple steady states of the reactor model without the need to use any iteration. The parametric continuation method is used to determine a curve whose each point is a solution of the tested model. Therefore, the starting point must be very precisely designated so that it lies on this curve. Otherwise, the result is a graph that deviates from the correct graph. However, this condition is not required when the homotopy method is also introduced into the calculations. The starting point can then be a point with any coordinates. Different curves are also obtained, but the homotopy method ensures that each of them passes through the point where the parameter p = 1. The solution we are looking for in the model is just such a point. This is undoubtedly a big advantage resulting from the combination of both above-mentioned methods.

Modeling of an ammonia decomposition membrane reactor including purity with complex geometry and non-isothermal behavior

A fully coupled mass, momentum, and heat balance model was constructed in axisymmetric 2D for an ammonia decomposition packed bed membrane reactor using computational fluid dynamics and compared to experimental results for a Pd/YSZ membrane surrounded by Ru/Al2O3 catalyst. In addition to the complex geometry of the fittings used to seal the membrane, a total of 16 design variables were found to be required to fully specify the tubular integrated membrane reactor. Aside from emissivity, all input variables were experimentally determined or obtained from tabulated material property data, and no correlation fitting was performed. Experimental data were obtained for temperatures of 450 °C–530 °C, trans-membrane pressures of 0 MPa–0.4 MPa, and gas hourly space velocity feed rates of 375 h−1 to 620 h−1, chosen such that the ammonia conversion and hydrogen recovery spanned a broad range with maximum values of 99.9 % conversion or 88 % recovery with greater than 99.8 % purity. The model was able to successfully determine the ammonia conversion and hydrogen recovery of the experimental results to within an average error of −0.31 % and −2.4 %, respectively. The purity was determined within +0.0071 %, but experimental detection limitations of the impurities affected the fit between experiment and model of the N2 and NH3 in the permeate. The sensitivity of the model to various assumptions and input variables was explored. Notably, the inclusion of purity is a rarity in published models and this study adds to the discussion on the ability of modeling to predict high purity results. Compared to the relatively minimal effects of using the full geometry, the inclusion of heat transfer and radial diffusion were critical in successfully predicting the experimental results.

Low-Density Polyethylene – New insights into an old material under comparative studies using SEC-MALS, AF4-MALS, HT-HPLC and 2D-LC

LDPE can be produced by different types of autoclave or tubular reactors, which can also be cascaded. An important effort is to obtain materials with autoclave-process equivalent properties from tubular technology due to economic reasons. In this way, the molecular understanding of the materials attains a key role. Five LDPE materials were characterized, covering three applications (extrusion coating, blow molding, and film blowing) as well as three reactor technologies (type I autoclave, tubular type, and type II autoclave). SEC-MALS, SEC-IR, AF4-MALS, HPLC, and 2D-LC allowed a detailed characterization of the samples’ molar mass and branching structure while providing a unique opportunity for technique comparison. This allowed for an unprecedented understanding of the differences in molecular structure and the influence of application vs. reactor technology driven differences.Overall, SEC-IR-MALS was found to provide the most versatile information, making it an excellent choice for an initial characterization. Furthermore, the results indicate that the intended application (and thus property profile) influences LDPE structure much more than reactor technology. All five studied samples exhibit differences in molar mass distribution, short-chain as well as long-chain branching. Yet, the three extrusion coating samples (each derived from a different reactor type) appeared notably similar to each other with regard to each parameter.

Interchangeable modular design and operation of photo-bioreactors for Chlorella vulgaris cultivation towards a zero-waste biorefinery

This study explores diverse cultivation modes for Chlorella vulgaris within a biorefinery at pilot scale that produces both biodiesel by transesterification of waste frying oils and syngas by gasification of organic wood waste. Given microalgae's comparatively modest biofuel yield relative to principal biorefinery products, the microalgae cultivation process is designed on the biofuels production rates. Liquid and gaseous waste streams are recycled inside the biorefinery: crude glycerol is mixed with wood to enhance the quality of syngas, wastewater is fed to microalgae so as flue gas. Also, the oil extracted from microalgae contributes to produce biodiesel and the waste cells are gasified.Considering that the optimal fit for each cultivation mode varies with the shape of the reactor, we propose a modular approach to assemble them in batteries of tubular, bubble flow, and airlift reactors, and present an operating design criterion that can fulfill the mass balance of the plant by adding/transforming the number of units inside the different batteries. Methods to adjust the operating conditions and control the operating parameters are also discussed.The designed configurations were operated recycling nominal waste streams of about 30 L d−1 of wastewater and 90 Nm3 h−1 of flue gas. Results confirm that the most advantageous one, in terms of volume per recycled waste streams, is a battery of 16 airlift reactors, operating in mixotrophic mode, with growing rate of 0.427 d−1, yield of 3.06, glycerol conversion 39 %, CO2 removal 64 % of inlet 6–10 %(mol) concentration. The same nominal waste streams can also be managed by 40 tubular reactors in almost heterotrophic conditions coupled with 12 bubble columns in autotrophic conditions; working respectively at growing rates of 0.395 d−1 and 0.362 d−1 and yields of 2.94 and 2.84. The battery of tubular reactors reached a glycerol conversion of 45 % and the array of bubble columns removed about 51 % of inlet 12–20 %(mol) CO2 concentration. A complete comparison is reported also in terms of dimensionless numbers and pumping/mixing requirements.

Hybrid-process including electrocoagulation for the real carwash wastewater treatment using a new continuous undivided tubular reactor

A coagulation-based continuous tubular electrochemical reactor has been designed to treat real carwash wastewater in a flow rate of 100 mL/min. This reactor made of an ordinary iron tube cathode with a commercial aluminum rod anode at the center. Equipment and chemicals needed for this method can be easily and cheaply obtained through non-scientific commercial sources. The one-factor at a time approach was used to investigate the effects of operating variables. Current density, flow rate, electrolysis time and electrode material were selected as independent variables while COD removal was considered as the response function. The experimental results showed that the proposed method can remove 89 % of COD from 10 liters of carwash wastewater in a "single-pass" and more than 99 % in a "double-pass" through the flow reactor. This reactor has short treatment time, low energy consumption, favorable mass transfer and low ohmic drop and does not need to adjust the pH or add electrolyte additionally to save costs. Also, this approach is resistant to undesirable phenomena such as passivation of the electrode surface, cell polarization, electrode surface fouling and reduction of electrical conductivity that may occur during electrolysis. The treated wastewater can be reused in the carwash industry as well as for irrigated agriculture.

Anaerobic Co-Digestion of Cattle Manure and Brewer’s Residual Yeast: Process Stability and Methane and Hydrogen Sulfide Production

Anaerobic co-digestion (AcoD) of animal waste and agro-industrial by-products has been widely studied and employed to increase biogas production potential and enhance process stability. This study evaluated the AcoD of cattle manure (CM) and brewer’s residual yeast (RY) in semi-continuous biodigesters, focusing on energy potential (biogas and methane yields) and process stability. Four treatments were assessed, each with different proportions (% of volatile solids) of CM and RY: 100:0, 88:12, 78:22, and 68:32. Trials were conducted in 30-L tubular reactors at room temperature with a hydraulic retention time of 30 days. The inclusion of RY led to a gradual rise in biogas and methane production, with more significant reductions in solid content than mono-digestion of CM. The addition of RY resulted in daily CH4 production increases of 18.5, 32.3, and 51.9% for treatments with 12, 22, and 32% of RY, respectively, compared to the control treatment. Therefore, AcoD demonstrated a higher potential for energy recovery. However, RY introduced elevated H2S levels in the biogas. Caution is advised when adding this co-substrate to AcoD due to potential process influence and biogas application restrictions.

Spatiotemporal operando UV–vis spectroscopy: Development and mechanistic alternation of CO oxidation on Pt/Al2O3 on the reactor scale

Operando methodologies are widely used in heterogenous catalysis to understand unique state of catalyst materials emerging under specific reaction conditions and to establish catalyst structure-activity relationships. Recent studies highlight the importance of combining multiple operando techniques (multimodal approach) to gain complementary information as well as looking into chemical and material gradients and spatial variations on the reactor scale. In this work, we developed an operando UV–vis diffuse reflectance spectroscopy (DRS) setup compatible with a common fixed-bed tubular reactor. The design is based on optical calculations, validation experiments and signals considerations. A spatial resolution of 1 mm along the axial direction of the reactor was successfully demonstrated and combined with a time resolution of seconds with good signal to noise. CO oxidation over Pt/Al2O3 was performed as a proof of principle experiment demonstrating the capabilities of the new setup. The information gained by the space-resolved operando UV–vis DRS was combined with other space-resolved operando studies such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), gas sampling and temperature profiling. The study shows that the nature of active sites (Pt redox state) and thus the reaction mechanism alter with reaction temperature and also in space. Spatiotemporal UV–vis DRS is also demonstrated, showing the capability for transient studies with space-resolution.

Understanding of gas-phase methane pyrolysis towards hydrogen and solid carbon with detailed kinetic simulations and experiments

Methane (CH4) pyrolysis is studied in a tubular flow reactor for the production of hydrogen and solid carbon by combining kinetic modelling, numerical simulation and experiments in a high-temperature flow reactor. Operating conditions are varied such as temperature in the range of 1273–1873 K, hydrogen addition to the feed with a molar H2:CH4 ratio between 0 and 4, and residence time in the range of 3–7 s. Elementary-step reaction mechanisms consisting of pyrolysis and carbon coupling reactions among C1, C2, aromatic and polycyclic aromatic hydrocarbon species are used in the numerical simulations of the species profiles in flow direction. A thermodynamic analysis is performed to acquire the boundary conditions for operation as well to estimate probable by-products (C2H2, C2H4, C2H6, C6H6, C16H10 etc.) over the temperature range. Gas-phase kinetic modelling is performed revealing that CH4 conversion starts at temperatures above 1273 K. Higher temperatures increase CH4 conversion and H2 yield peaking at 1573 K. The cooling temperature gradient downstream of the hot zone in the reactor causes reverse reactions in gas-phase suppressing CH4 conversion. H2 addition to the feed is found to be a crucial parameter for controlling the by-product formation. In the experimental study, a solid carbon yield of 84 % is achieved while gaseous by-products remain less than 1 mol-% at 1673 K, H2:CH4 ratio of 2, and residence time of 5 s. Gas-phase reactions are found to be coupled to surface reactions at higher temperatures.

An innovative pillow-plate reactor for the synthesis of methanol from biogas: A simulation study

This work investigates the performances of a pillow-plate heat exchanger utilized as reactor for small-scale methanol synthesis. When downscaled, multi-tubular packed bed reactors are complicated to use since they undergo rapid losses in catalyst activity. A possible pathway to improve the unit performances is to diminish the tubes diameter and number. As this kind of reactors is governed by convective heat transfer, though, the use of long tubes is required to keep the mixture velocity high. This leads to the use of very long reactors, which cannot be easily realized with traditional designs. In order to tackle this issue, we propose the utilization of an innovative design, the pillow-plate reactor, increasing heat and mass transfer and the unit compactness. The study compares the performances of a packed-bed and a pillow-plate reactor through temperature profiles and methanol productivity at varying reactor lengths (1 – 6 m). It is proved that the pillow-plate unit, unlike the multi-tubular one, well manages scale reduction: when 1 m long reactors are employed, the outlet methanol fraction is close to equilibrium (5.8% vs. 4.9% for packed beds) and the hot-spots are well controlled (537 K vs. 557 K for tubular reactors). Moreover, it is also shown that the distance of metal layers in the pillow arrangement remarkably influences heat exchange, which is very effective for close layers, with a hot-spot of 518 K with a 3 mm gap, and much worse for the 12 mm design (552 K).

Orthogonal collocation based‐optimization of fouling resistance for industrial low‐density polyethylene production in a tubular reactor

AbstractIn tubular reactors, fouling issues are caused due to two reasons. One is the heating–cooling prerequisite, and the other is the exothermic nature of the low‐density polyethylene (LDPE) polymerization process. These issues must be considered while optimizing LDPE production to provide maximum productivity and a safe operation. However, it is not a simple process because the conversion of the monomer (XM) is generally related to significant profits. This conversion might be performed at high reaction temperatures, resulting in fouling formation. Therefore, in this research, a study of dynamic optimization to find the most efficient production of LDPE in the presence of fouling resistance (Rf) restrictions is conducted. An Rf is employed as a measure of fouling. To establish the highest reactor Rf , this study employs variations in the heat transfer coefficient (U) calculated from industry data. This dynamic optimization study addresses the optimization challenges using dynopt coded programming based on orthogonal collocation (OC) and sequential quadratic programming methodologies. Beforehand, the LDPE model is validated with industrial data. This study evaluates three possibilities to determine the most optimum reactor performance. The most optimum reactor output is determined from the constrained maximum conversion, which gave 32.15% conversion, while the was effectively met at 47.37cm2 s K/cal.

A solar flow photo-reactor for antibiotic removal from aquaculture effluents using TiO2/carbon quantum dots

Effluents contaminated with antibiotics must be treated before reuse or even discharge into the aquatic environment, avoiding the increase of antimicrobial resistance (AMR) – a major public health problem of the 21st century. Little is known regarding the natural solar photodegradation of antibiotics in tubular reactors operated under flow mode and even less concerning the application of photocatalysts. The use of photocatalysts is considered a promising strategy for a sustainable solar-driven removal of antibiotics from effluents. In this work, the photodegradation of two antibiotics widely used in aquaculture, namely, sulfadiazine (SDZ) and oxolinic acid (OXA), was investigated under solar flow mode in the absence and presence of carbon quantum dots (CQDs) coupled with titanium dioxide (TiO2) (4% (w/w)). The obtained results showed that TiO2/CQDs (4% (w/w)) enhanced the photodegradation of both antibiotics, which is highly beneficial for their application in the treatment of aquaculture effluents. The accumulated UV energy needed for SDZ removal using the photocatalyst was less than 4 kJ L−1 in both simulated freshwater (phosphate buffer solution (PBS)) and simulated brackish water (sea salt solution (SSS)), while for OXA less than 5 kJ L−1 and around 15 kJ L−1 were needed for removal in PBS and in SSS, respectively. Moreover, results demonstrated that the proposed photocatalytic treatment was also efficient in the elimination of OXA and SDZ antibacterial activity, either in PBS or SSS. Therefore, photocatalysis under flow mode using TiO2/CQDs constitutes a promising and sustainable treatment for antibiotics’ efficient removal from aquaculture effluents.

A fast synthetic strategy for quick preparation and optimization of platelike MFI crystals

The demand for high aspect ratio zeolite crystals has been increasing dramatically for many applications, ranging from catalysis to membrane separations. However, manufacturing such platelike crystals usually requires energy-intensive and time-consuming synthesis procedures. Here, by employing a thin-wall tubular reactor, we report for the first time a fast synthetic strategy that yields preferentially-b-oriented platelike MFI crystals within minutes of hydrothermal treatment. Various synthesis conditions such as hydrolysis, precursor aging, chemical compositions, etc. can be quickly optimized within days. Such optimization resulted in highly crystalline platelike crystals with lateral dimensions up to ∼5 μm length in c-axis or ultra-thin crystals with ∼25 nm thickness. Meanwhile, non-platelike MFI crystals can even reach 135 μm lateral size in 24 h. This fast synthetic strategy can be further generalized for the preparation and optimization of diverse important materials including MOFs, COFs, and other zeolites, benefiting both fundamental research and practical applications.

Continuous Treatment of Refractory Wastewater from Research and Teaching Laboratories via Supercritical Water Oxidation–Experimental Results and Modeling

Teaching and research laboratories generate wastes of various compositions and volumes, ranging from diluted aqueous solutions to concentrated ones, which, due to milder self-regulation waste-management policies, are carelessly discarded, with little attention given to the consequences for the environment and human health. In this sense, the current study proposes the application of the supercritical water oxidation (SCWO) process for the treatment of complex refractory wastewater generated in research and teaching laboratories of universities. The SCWO, which uses water in conditions above its critical point (T > 647.1 K, p > 22.1 MPa), is regarded as an environmentally neutral process, uniquely adequate for the degradation of highly toxic and bio-refractory organic compounds. Initially, the wastewater samples were characterized via headspace gas chromatography coupled with mass spectrometry. Then, using a continuous tubular reactor, the selected operational parameters were optimized by a Taguchi L9 experimental design, aiming to maximize the total organic carbon reduction. Under optimized conditions—that is, temperature of 823.15 K, feed flow rate of 10 mL min−1, oxidizing ratio of 1.5 (50% excess over the oxygen stoichiometric ratio), and sample concentration of 30%—TOC, COD, and BOD reductions of 99.9%. 91.5% and 99.2% were achieved, respectively. During the treatment process, only CO2, methane, and hydrogen were identified in the gaseous phase. Furthermore, the developed methodology was applied for the treatment of wastewater samples generated in another research laboratory and a TOC reduction of 99.5% was achieved, reinforcing the process’s robustness. A thermodynamic analysis of SCWO treatment of laboratory wastewater under isothermal conditions was performed, using the Gibbs energy minimization methodology with the aid of the GAMS® 23.9.5. (General Algebraic Modeling System) software and the CONOPT 4 solver. Therefore, the results showed that SCWO could be efficiently applied for the treatment of wastewater generated by different teaching and research laboratories without the production of harmful gases and the addition of hazardous chemicals.

Catalytic Performance of Bimetallic Cobalt–Nickel/Graphene Oxide for Carbon Dioxide Reforming of Methane

The design of economical and robust catalysts is a substantial challenge for the dry reforming of methane (DRM). Monometallic nickel-based catalysts used for DRM reactions had comparable activity to noble metals. However, they turned out to be less stable during the reactions. As a continuation of the interest in synthesizing catalysts for DRM, this paper evaluates the catalytic performance of bimetallic Co–Ni catalysts regarding their synergy effect, with graphene oxide (GO) as support for the first time. The synthesized bimetallic catalysts prepared via the wet-impregnation method were characterized using N2 physisorption analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The catalytic test was performed in a stainless-steel tubular reactor in atmospheric conditions with a reaction temperature of 800 °C, time-on-stream (TOS) of 300 min and CH4: CO2 being fed with a ratio of 1:1. The bimetallic 10 wt%Co–10 wt%Ni/GO and 20 wt%Co–10 wt%Ni/GO catalysts had a similar BET specific surface area in N2 physisorption analysis. The XRD pattern displayed a homogeneous distribution of the Co and Ni on the GO support, which was further validated through SEM–EDX. The conversion of CO2, CH4, and H2 yield decreased with reaction time due to the massive occurrence of side reactions. High conversions for CO2 and CH4 were 94.26% and 95.24%, respectively, attained by the bimetallic 20 wt%Co–10 wt%Ni/GO catalyst after 300 min TOS, meaning it displayed the best performance in terms of activity among all the tested catalysts.

Integral recycling of polyester based end-of-life fibre reinforced plastic waste towards syngas generation

Valorisation of chemical compounds derived from the thermal decomposition of the plastic matrix in fibre reinforced plastic waste is claimed as crucial for cost-effective recycling of this waste. This work, validated the application of a thermal treatment (900 °C) to the volatiles generated from the pyrolysis of four end-of-life glass fibre reinforced polyester waste in a fixed bed tubular reactor placed in series with the pyrolysis reactor. Thermal treatment of pyrolysis volatiles' improves current scenario by transforming the hazardous liquids and low quality gas into almost non-existent aqueous liquid and maximised synthesis gas stream (CO + H2).

Criteria for the use of 1D and 2D models in catalytic membrane reactor modeling

A criterion was developed to determine the necessity of using 1D or 2D methods for modeling a concentric tubular membrane reactor for hydrogen-producing reactions. Four dimensionless parameters were defined to provide a complete description of the physical and chemical systems, and the effects of each parameter on the difference between a 1D and 2D model were explored. The membrane reactor geometry consisted of a tube-and-shell configuration with a catalyst bed in the tubular section and a perm-selective membrane in the interphase. The four dimensionless parameters consisted of the Damköhler number (Da), which relates the reaction and axial convection rates, the Péclet number (Pe), which relates the radial diffusion and axial convection rates, the transport parameter (θ), which relates the axial convection and membrane permeation rates, and the equilibrium parameter (ε), which is a measure of the favorability of the reaction. A cutoff at which 1D and 2D model results have less than a 1% difference in final concentrations was used to define a critical Pe value, or Pecrit. Then, a criterion equation was fitted using non-linear regression so that any system can be calculated and compared against Pecrit. Using this criterion, a model above the cutoff (Pe > Pecrit) can reduce computation time by selectively calculating a simple 1D model for conditions, while a model below the cutoff (Pe ≤ Pecrit) should use a more computationally expensive 2D model to assure accuracy. The final criterion was validated against literature data for both 1D and 2D models.

Continuous generation of cross-linked polymer nanoparticles employing an ultrasonic microreactor

In this article, a new system employing an ultrasonic microreactor coupled with a tubular reactor is presented for the continuous generation of polymer nanoparticles. The continuous generation of cross-linked polymer nanoparticles utilizing the monomer butyl methacrylate and the cross-linker ethylene glycol dimethacrylate is demonstrated. Firstly, the miniemulsion polymerization of a monomer-in-water miniemulsion is studied in a batch system. Secondly, a coiled tubular reactor is employed for the continuous polymerization of the miniemulsion generated by an ultrasonic microreactor. Finally, the influence of monomer volume fraction and surfactant concentration on the synthesized polymer nanoparticles is studied. Polymer particles in a size range of 50–250 nm are synthesized and a high polymerization conversion is achieved utilizing the system demonstrated in this article.

An efficient separation for fluoride-ions from water supplies by ion precipitate flotation: Pilot scale study with generation of coagulative bubbles

Bubble surface modification is a promising technique that enables to increase the efficiency of a treatment that aims to remove a certain particle with lower consumption of chemical inputs. In this study, the so-called coagulative bubbles were generated from a mixed system consisting of amphoteric surfactant (Cocamidopropyl betaine, CAPB) and inorganic polymer coagulants (aluminum sulfate and calcium chloride) for the removal of fluoride ions present in groundwater destined for human supply. The critical micellar concentration (CMC) of CAPB was 0.26 mmol L−1. The coagulant bubbles (CB) were generated from pressurizing the coagulant solution in distilled water and applied continuously in a helical tubular reactor. The CB treatment method provided higher fluoride removal compared to conventional treatment with simple coagulant application. The CBs generated with Al made it possible to remove approximately 98 % of the initial amount of fluoride measured (3.5 mg L−1) with a dosage of 31 mg L−1 of Al; feed flow rate of 20 L min−1; pH 6 ± 0.5; and saturation pressure of 3 atm. This same operation, but without generation of CBs (regular atmospheric pressure), allowed the removal of 67 % of the initial fluoride concentration.