Regeneration Of Solution Research Articles

Processes of methanol regeneration from water-methanol solutions in the oil and gas industry

In oil and gas production, treatment and transportation technologies, gas hydrates cause serious problems associated with disruption of these technological processes. The traditional and most common method of combating gas hydrates in the oil and gas industry is the use of methanol as a hydrate inhibitor. The specific consumption indicators of methanol consumption as an inhibitor of the formation of gas hydrates directly depend on the composition of the extracted products, as well as on the technology for preparing the extracted products for transportation.
 Gas hydrates represent one of the major economic and safety problems in the oil and gas industry in the exploration, production, processing and transportation of gas and hydrocarbons.
 This article analyzes modern methods for methanol regeneration at oil and gas industry enterprises, and describes in detail the methods and parameters of processing plants that are used for the regeneration of water-methanol solutions. The advantages and disadvantages of advanced methods of water-methanol solutions regeneration are described. As a result of the review of existing technologies, the distillation method was determined to be the most preferable, as the most proven and widely used method today.

Environmentally safe technology of waste processing of galvanic production

It is known that waste is difficult to purify using existing reagent methods to the standards of the MPC. In addition, the formed sediments contain poorly soluble hydroxy compounds of heavy metals and gypsum, which makes it impossible to dispose of iron- and copper-containing electroplating sludges. The purpose of the study was to study the possibility of ion exchange separate and simultaneous extraction of iron and copper ions from acidic solutions of pickling and copper plating in galvanic production to obtain ferrites. In the course of research, the highly acidic cation exchange resin Dowex HCR S/S in the H+ form was chosen as the cationite. The choice of a strongly acidic cationite is justified, based on the fact that cationites of this type are able to easily lose hydrogen ions due to their displacement from the cationite matrix by other cations of the solution. The sorption processes of iron (II) and copper (II) ions were carried out under dynamic conditions. In the course of experimental studies, it was shown that with an increase in the concentration of sulfuric acid, the full exchangeable dynamic capacity of the cationite significantly decreases both during the sorption of iron ions and during the sorption of copper ions. For iron-containing solutions, full dynamic exchange capacity decreases from 1.39 g-eq/dm3 in the absence of H2SO4 in the initial solution and decreases to 0.3-0.46 g-eq/dm3 at a concentration of sulfuric acid at the level of 1-3 g/dm3. An increase in the concentration of iron (II) ions leads to a significant increase in full dynamic exchange capacity, even with a concentration of sulfuric acid of 8 - 13 g/dm3, full dynamic exchange capacity was at the level of 1.35 g-eq/dm3, which corresponds to the level of sorption of diluted solutions even in the absence of acid. However, the total concentration shows that the efficiency of sorption of metals from acidic solutions remains quite high and increases with the increase of the initial total content of sorbed ions. The main indicator used when choosing an ion exchange method is the possibility of effective regeneration of the cation exchange material. When using 5% solution of sulfuric acid already at the specific consumption of the regeneration solution, it was possible to achieve a degree of regeneration at the level of 95-98%, and when using 10% solution, the degree of regeneration reached 100%. According to the developed technological scheme, regeneration solutions are processed by precipitation into magnetite in a ferritizer reactor. To remove iron ions from concentrated iron-containing regeneration solutions by the ferrite method in order to obtain ferrite particles (magnetite) with maximum magnetic properties, a mixture of Fe (II) and Fe (III) sulfates was used with their concentration ratio K = [Fe2+]/[Fe3+] = 0.5, as a stable relationship between magnetic properties and sediment volume was noted. At maximum magnetic properties, the sediment volume is minimal, and vice versa. Obtaining highly dispersed magnetic particles from a mixture of ferric and ferric sulfates by precipitating them with 10% NaOH solution during heating allows to significantly reduce the duration of the process, simplify it and increase the productivity of the equipment. To obtain magnetic particles of copper ferrites from regeneration solutions by precipitation with alkali at normal temperatures, the concentration ratio K1 = [Fe2+]/[Cu2+] = 3.15-7.76 should be maintained. With an increase in the concentration of Cu2+ ions, there is an increase in the period of crystallization of the obtained sediments and their acquisition of magnetic properties. The formed ferrite material can be used for environmental purposes as a valuable raw material for carbon monoxide neutralization catalysts, as part of alkaline cement for concrete products, or sent for safe disposal. The obtained results on the application of ion-exchange extraction of iron and copper ions from acidic solutions of galvanic production are expedient as the first stage of complex ecologically safe processing of galvanic wastes with the production of ferritic materials for industrial use.

Effects of competitive cations and dissolved organic matter on ammonium exchange and up-concentration properties of ion exchangers from domestic wastewater under multicycle exchange - regeneration operation

This study aimed to investigate the impact of competitive cations and dissolved organic matter (DOM) on ammonium exchange and up-concentration properties of ion exchangers for domestic wastewater treatment during the multicycle exchange - regeneration operations. Three ion exchangers, including zeolite, strong acid cation resin and 4A molecular sieve (MS), all showed good NH4+ separation and up-concentration properties in 30 exchange - regeneration cycles. The exchange capacities of zeolite, resin, and MS decreased by 8.2 %, 10.4 %, and 4.8 % in the presence of Ca2+ and Mg2+, while DOM only impaired the exchange ability of zeolite. The up-concentration factors of zeolite, resin, and MS were 5.1, 11.5, and 5.0, respectively. Isothermal tests and breakthrough curves confirmed that long-term salt regeneration slightly reduced the exchange capacity, and the presence of competitive cations and DOM shortened the breakthrough time. Elemental mass balance further demonstrated that Ca2+ and Mg2+ were easily trapped by ion exchangers and could be released into the regeneration solution, which should be precipitated to avoid accumulation for long-term cyclic operation. Morphological analysis indicated that the presence of Ca2+ and Mg2+ would cause the resin to crack. Overall, for domestic wastewater treatment, the resin exhibited the highest NH4+ capture ability and up-concentration properties with low resistance to Ca2+ and Mg2+ contamination, while silicate exchangers with a regular and compact structure had higher durability but lower up-concentration properties.

Efficient Sequential Detection of Two Antibiotics Using a Fiber-Optic Surface Plasmon Resonance Sensor.

Antibiotic residues have become a worldwide public safety issue. It is vital to detect multiple antibiotics simultaneously using sensors. A new and efficient method is proposed for the combined detection of two antibiotics (enrofloxacin (Enro) and ciprofloxacin (Cip)) in milk using surface plasmon resonance (SPR) sensors. Based on the principle of immunosuppression, two antibiotic antigens (for Enro and Cip) were immobilized on an optical fiber surface with conjugates of bovine serum albumin using dopamine (DA) polymerization. Each single antigen was bound to its corresponding antibody to derive standard curves for Enro and Cip. The fiber-optic sensor's sensitivity was 2900 nm/RIU. Detection limits were calculated to be 1.20 ng/mL for Enro and 0.81 ng/mL for Cip. The actual system's recovery rate was obtained by testing Enro and Cip in milk samples; enrofloxacin's and ciprofloxacin's mean recoveries from the milk samples were 96.46-120.46% and 96.74-126.9%, respectively. In addition, several different regeneration solutions were tested to analyze the two target analytes' regeneration ability; NaOH and Gly-HCl solutions were found to have the best regeneration ability.

A feasibility study of hybrid forward osmosis-solar evaporation process using melamine sponge loaded with polypyrrole (PPy@MS) solar evaporator for desalination of brackish water

The application of the osmotic pressure-driven forward osmosis (FO) process is limited due to the high costs for regeneration and replacement of draw solution. A hybrid FO-solar evaporation (SE) hybrid process was systematically investigated to produce fresh water from desalination of brackish water. The melamine sponge loaded with polypyrrole (PPy@MS) composite material was synthesized by loading light-absorbing polypyrrole (PPy) into a network of melamine sponge (MS) substrates. As a solar evaporator, PPy@MS material showed high light absorption, water evaporation, and anti-pollution abilities in the FO-SE process. Feasibility for operating the hybrid desalination process was studied in terms of solar evaporation rate, salinity tolerance, hydrophilicity, and mechanical strength of PPy@MS, and desalination performance, including water flux, ion removal, reverse salt flux, and membrane fouling. Characterization results indicated that PPy@MS performed a high interfacial molecular transformation, solar energy accessing ability, salt-tolerance, and mechanical stability in a long-term FO-SE operation, achieving an evaporation rate up to 2.80 kg·m−2·h−1 (1 sun, 1 h) and ion removal rate of 99.9 %. A maximum evaporation flux of 17.4 L·m−2·h−1 was monitored in the FO-SE process using 2 M NaCl as the draw solution (FO film area: 5 cm2). Solar-driven evaporation via PPy@MS was able to assist the continuous operation of the FO-SE process with high water flux. This work proposes a novel sustainable hybrid FO-SE technology for FO desalination of brackish water and other saline water bodies.

A modeling and experimental comparative study of a closed-loop forward osmosis-nanofiltration and standalone nanofiltration systems for fouling-prone wastewater treatment

The forward osmosis-nanofiltration (FO-NF) process presents a potential alternative for the treatment of wastewater effluents, compared to pressure-driven systems like reverse osmosis (RO)/nanofiltration (NF). This work bridges the gap in exploring the impact of continuous draw solute regeneration in FO-NF hybrid, and its influence on the performance over standalone NF at module-scale. The Speigler-Kedem model, along with the concentration polarization model, is used to describe the local mass transport in the membrane. Following this, the combined mathematical models for FO and NF are integrated into the hybrid FO-NF system at module-scale. Subsequent process optimization reveals that NF hydraulic pressure and inlet draw concentration control the NF retentate concentration and then simulate the desired operating conditions for the hybrid system when the NF retentate stream is directly used as a draw solution for the FO process. Further results show that in non-fouling feed solution, the FO-NF system is inferior to standalone NF in terms of SEC. In contrast, for fouling-prone feed solution, the standalone-NF performance degrades with time, which gradually mitigates water recovery from 40 to 15.6 % while increasing the SEC from 0.89 to 2.38 kWh/m3. At the same time, the FO-NF hybrid system performs better with Na2SO4 and MgSO4 as draw solutes with nearly constant water recovery of 32.6 % and 28.6 %, and negligible SEC fluctuations of 3.26 kWh/m3 and 4.70 kWh/m3 for the two draw solutes respectively. Despite this, compared with other state-of-the-art desalination technologies, the FO-NF hybrid exhibits comparably lower water cost (average 0.31 USD/m3) and effectively handles fouling-prone wastewater.

Fly ash as a cost-effective catalyst to promote sorbent regeneration for energy efficient CO2 capture

The use of catalysts to promote sorbent regeneration is currently considered an effective method to reduce the energy required in CO2 capture processes. Aiming at identifying stable and cost-effective catalysts with high CO2 desorption efficiency, here we investigated the performance of fly ash (FA) during thermal regeneration of aqueous amine solutions. The desorption rate, cyclic capacity and heat duty of a CO2-saturated aqueous ethanolamine with the addition of FA were experimentally measured, and the results were compared with those obtained for the same solution without and with eight different catalysts. Experimental results showed that catalysts significantly improved the regeneration compared to the non-catalyzed system, and FA was the most efficient of these. Further studies of CO2 desorption at different temperatures showed that FA provided desorption performance comparable to that of the non-catalyzed system at temperatures at least 5 °C higher and always significantly reduced the heat duty at the same temperature, especially at the beginning of the process. Finally, recycling tests demonstrated that FA had good stability and its catalytic efficiency remained high even after 20 cycles. In conclusion, FA could be considered a cost-effective catalyst for energy-efficient CO2 capture, deserving further investigation to promote its application in industrial-scale plants.

Integrating aesthetics and efficiency: AI-driven diffusion models for visually pleasing interior design generation

The interior design suffers from inefficiency and a lack of aesthetic appeal. With the development of artificial intelligence diffusion models, using text descriptions to generate aesthetically pleasing designs has emerged as a new approach to address these issues. In this study, we propose a novel method based on the aesthetic diffusion model, which can quickly generate visually appealing interior design based on input text descriptions while allowing for the specification of decorative styles and spatial functions. The method proposed in this study creates creative designs and drawings by computer instead of from designers, thus improving the design efficiency and aesthetic appeal. We demonstrate the potential of this approach in the field of interior design through our research. The results indicate that: (1) The method efficiently provides designers with aesthetically pleasing interior design solutions; (2) By modifying the text descriptions, the method allows for the rapid regeneration of design solutions; (3) Designers can apply this highly flexible method to other design fields through fine-tuning. (4) The method optimizes the workflow of interior design.

Enhancing Public Space Accessibility and Inclusivity in Residential Neighbourhoods: A Methodological Framework and Pilot Application

The paper adds to the debate on urban transformation, which plays a significant role in improving quality of urban life and liveability of public spaces, as also stated in UN Sustainable Development Goal No. 11. The research aims to test a methodology for identifying an abacus of urban regeneration interventions to enhance attractive and critical nodes through accessibility and inclusivity. The quality of the system of connections between polarities, the promotion of active mobility, zero soil consumption and the renaturalisation of urban spaces are fundamental criteria to define urban regeneration solutions. The proposed approach develops on two levels: a GIS-based spatial analysis of urban data and a participatory process. The innovative planning process is tested on the San Leonardo neighbourhood in the Municipality of Parma, Italy, which allows us to verify the potentials and limitations of the procedure, identifying future work perspectives. Moreover, the application allows us to check the replicability in other urban contexts, possibly envisaging other applications to more case studies. Our results consist of the identification of the vocations and the critical aspects of nodes and axes to regenerate urban space in medium-sized and large cities’ suburbs.

Vapor Sublimation and Deposition Polymerization to Fabricate a Directional Scaffold for Guiding Tubular Dentin Regeneration

AbstractDental caries, or tooth decay, is a widespread problem and is generally considered irreversible, yet a regeneration solution exists to cure them. In this study, a multifunctional and biocompatible dental scaffold is fabricated by a unique vapor sublimation and deposition polymerization process with the well‐accepted material Parylene, resulting in the construction of a 3D and porous polymer scaffold that accommodates living cells and a combination of growth factor molecules in a single fabrication process, which differentiates the coating formation from a conventional vapor process. Physically, a directional interior structure is constructed to guide dental pulp stem cells (DPSCs) attachment and alignment. Biochemically, necessary growth factors, including Wnt‐3a and FGF‐2, are incorporated within the scaffold during fabrication to guide the cell differentiation of odontogenesis. The synergistic effects of the attachment and alignment of DPSCs, as well as the biocompatibility and odontogenic activities of the components accommodated in the scaffold, result in the upregulation of the cell differentiation into odontoblasts, as shown by the morphology of odontoblasts and the expressions of odontogenesis markers. Thus, the reported fabrication technique and its products represent an alternative approach for dentin regeneration in dental caries and tooth decay.

Sodium functionalised carbon nanofibers draw solution for a solar-thermal forward osmosis water desalination system

Desalination offers the potential to bridge the demand-supply gap in the increasing global freshwater scarcity, with the forward osmosis (FO) technique appearing as an attractive solution amongst the various desalination technologies. However, the significant energy demand encountered during the draw-solute recovery process in FO desalination is considered the major anathema amongst other contending factors for which the allure of FO as a desalination technology becomes questioned. Consequently, a potentially innovative draw solution (DS) regeneration strategy, enabling the circumvention of the energy requirements associated with the recovery stage in FO desalination, is evaluated. The direct solar thermal FO (DSTFO) desalination concept is predicated on engineering and applying solar absorptive DS to directly leverage solar energy for solute recovery without recourse to electric power. In advancing the DSTFO concept, this study fabricated and evaluated a novel and highly osmotic sodium functionalised carbon nanofibres (Na/CNF) DS having a high osmotic pressure (93.9 bar), a low reverse solute flux (RSF) of 0.24 gMH, and a photothermal conversion efficiency of 63.49%, resulting in an evaporation rate of 1.85 kg/m2/hr under 2 suns of solar radiation. The DSTFO strategy offers a low-cost solution for enhancing water recovery and decreasing energy use in FO desalination systems.

Conjugate heat and mass transfer in vacuum membrane distillation for solution regeneration using hollow fiber membranes

To avoid problems such as low efficiency of liquid desiccant processes in high humidity environments, vacuum membrane distillation (VMD) solution regenerators are proposed. This study investigates the conjugate heat and mass transfer mechanism in the vacuum membrane distillation solution regeneration. The study reveals that the solution temperature and concentration in the hollow fiber membrane tube exhibit a tower-shaped distribution, with the lowest temperature near the membrane surface and the highest concentration at the outlet. The membrane flux decreases along the direction of the solution flow, ranging from 0.62 to 0.36 g/(m2·s). Increasing the solution flow rate and vacuum degree enhances the heat and mass transfer, while increasing the solution concentration reduces the heat and mass transfer. The Nusselt and Sherwood number formulas applicable to the VMD solution regeneration process were fitted, which is more accurate than the empirical formulas at atmospheric pressure. The resistance distribution during the solution regeneration process in VMD shows that the membrane-side resistance has a significant impact on the heat and mass transfer during solution regeneration, with the membrane-side thermal resistance accounting for 91 % of the total resistance in the heat transfer process and 67 % in the mass transfer process. The findings in this paper can more accurately guide the design of vacuum membrane distillation solution regenerators.

Regeneration of etching solution used in the production of printed circuit boards

Some waste waters containing copper are formed during the production of printed circuit boards. When these effluents are discharged into the reservoir, they must be diluted 140,000 times, and the treatment of these copper-containing effluents causes the copper loosing. The paper presents the results obtained during the study of electrochemical processing of copper-containing effluents formed at the stage of PCBs etching. The spent solution processing was realized in a membrane electrolytic cell. An increase in current density results in an increase in process speed. Along with a decrease in copper concentration in the solution, the hydrochloric acid was concentrated. It is shown that it is possible to regenerate the etching solution and obtain a metallic copper.

Alkaline Hydrothermal Treatment of Chabazite to Enhance Its Ammonium Removal and Recovery Capabilities through Recrystallization

The treatment of chabazite (CHA), a natural zeolite, with the alkaline hydrothermal method to improve its ion-exchange capacity is a widely adopted route by environmental scientists for the purpose of better ammonium (NH4+) removal from wastewater. This work addresses a noteworthy trend in environmental science, where researchers, impressed by the increased ion-exchange capacity achieved through alkaline hydrothermal treatment, often bypass the thorough material characterization of treated CHA. The prevalent misconception attributes the improved features solely to the parent zeolitic framework, neglecting the fact that corrosive treatments like this can induce significant alterations in the framework and those must be identified with correct nomenclature. In this work, alkaline-mediated hydrothermally treated CHA has been characterized through X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS) and it is concluded that the treated samples have been transformed into a desilicated, aluminum (Al)-dense framework of analcime (ANA) with a low silica–alumina ratio and with a strikingly different crystal shape than that of parent CHA. This treated sample is further examined for its NH4+ removal capacity from synthetic wastewater in a fixed-bed column arrangement. It achieved a maximum NH4+ removal efficiency of 4.19 meq/g (75.6 mg/g of NH4+), twice that of the parent CHA. Moreover, the regeneration of the exhausted column yielded a regenerant solution, with 94% reclaimed NH4+ in it, which could be used independently as a nitrogenous fertilizer. In this work, the meticulous compositional study of zeolitic materials, a well-established practice in the field of material science, is advocated for adoption by environmental chemists. By embracing this approach, environmental scientists can enhance their comprehension of the intricate changes induced by corrosive treatments, thereby contributing to a more nuanced understanding of zeolitic behavior in environmental contexts.

Amine-Functionalized Pencil Graphite Electrode for Simultaneous Determination of Dopamine and Uric Acid

In this study, an electrochemical transducer based on an Amine-functionalized cheap and disposable pencil graphite electrode (NPGE) is proposed for the simultaneous monitoring of Dopamine (DA) and Uric Acid (UA) in biological samples such as serum and urine. The prepared NPGE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the incorporation of amine groups significantly improved catalytic activity than the bare pencil graphite electrode (BPGE). Moreover, the electrode modification parameters and effects of different analytical variables such as sweep rate, pH of the supporting electrolyte solution, and possible interfering ions or molecules in quantification were optimized using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, DA and UA oxidation currents showed linear responses over the concentration range of 1.06-160 µM for DA and 30.06-150 µM for UA. The limit of detection (LOD) for DA and UA were estimated to be 0.94 and 1.26 µM, respectively. In addition, the transducer’s sensitivity of 5.47 µA.µM-1cm-2 for DA and 1.70 µA.µM-1cm-2 for UA were calculated. Aiming to reuse the transducer, a regeneration solution is proposed which could successfully remove the adsorbed oxidized products from the surface. Finally, the developed transducer’s performance was compared with the established clinical method. Figure 1

A Two-Dimensional Transport Model of Bipolar Membrane Electrodialysis for the Electro-Regeneration of Carbon Capture Solvents

Bipolar membrane electrodialysis (BPMED) is a promising technology that uses an electric field to split water into H+ and OH- ions. A repeating stack of cation selective, anion selective, and bipolar membranes are placed between two electrodes, creating a repeating pattern of acid, base, and diluting flow chambers. A major application of BPMED is the electrochemical solvent regeneration of capture solutions used in CO2 point source (PS) or direct air capture (DAC). Protons generated using BPMED can be used to shift the acid-base equilibria back to CO2, providing a more sustainable alternative to traditional thermal regeneration methods when integrated with renewable electricity sources. This method combines electrosynthesis and separation, producing a pure stream of CO2 for sequestration and a concentrated base stream.Despite its potential, current limitations to BPMED implementation for this application stem from a large power consumption and high membrane costs. In addition, gas bubbles in solution can cause high electrical resistances, and experimental studies of this phenomenon are challenging due to the small scale on which it occurs. To address these challenges, we present a two-dimensional model of BPMED for CO2 capture solvent recovery. This model depicts a single repeating cell triplet and was constructed using COMSOL Multiphysics version 6.1. The Navier-Stokes equations were implemented to compute a convection field, and the ionic species concentration was found by solving the Nernst-Planck equation. A source term in the concentration partial differential equations was implemented to account for ionic speciation and water splitting reactions, captured through kinetic rate expressions.Experimental validation was conducted on a PC Cell BED 1-4 recirculating batch system with a stack of seven cell pairs of PC acid 60 (anion selective), PC SK (cation selective), and PC Bip (bipolar) membranes. Good agreement between the model and experimental results across a range of conditions and variables demonstrates accuracy and robustness. The calculated pH and concentration profiles revealed that the majority of the speciation reaction takes place inside, or directly adjacent to, the bipolar membrane, including bubble nucleation. Bubbles form inside membrane pores and displace the electrolyte, greatly increasing the electrical resistance of the membrane, particularly when membrane porosity is low. However, the reaction plane location where bubbles are generated can be manipulated by increasing the channel width or reducing the applied voltage.Future research will focus on expanding to multiphase CFD simulations to investigate the effect on flow. Our two-dimensional model provides valuable insights into the complex and multifaceted nature of BPMED, offering a powerful tool for investigating small-scale processes and advancing the use of BPMED for CO2 capture solvent recovery. Figure 1

Effect of Ti-containing precursors on structure and adsorption performance of Li4Ti5O12 and Li2TiO3 oxides to Li+ ions

Using solid-phase synthesis method, Li4Ti5O12 and Li2TiO3 oxides were synthesized and used as adsorbents for Li+ ions. The physical–chemical properties were studied, using X-ray diffraction analysis, IR-spectroscopy, low-temperature adsorption–desorption of nitrogen, and scanning electron microscopy. It was shown that, using anatase as a Ti-containing precursor, single-phase oxides Li4Ti5O12 (d 26.5 nm, a 8.401 Å, V 569.5 Å3) and Li2TiO3 (d 26.5 nm, a 7.731 Å, V 462.1 Å3) with macro-mesoporous structure (ABET 11 and 16 m2/g, VBJH des 0.03 and 0.03 cm3/g, DBJH des 6 and 6 nm, respectively) and spherical-like morphology were obtained. For the samples obtained from rutile, an impurity of unreacted Ti-containing precursor was detected. The effect of the nature of Ti-containing precursors, concentration and temperature of HCl regeneration solution, and contact time on the degree of conversion to H-form and adsorption capacity of the obtained adsorbents was studied. The highest efficiency of ion exchange of Li+ ions with H+ (γH+ 96.7–100 %) was reached in conversion of adsorbents to H-form, during treatment with 0.1 M HCl at temperature of 70 °C for 48 h. Adsorbents H4Ti5O12 and H2TiO3 prepared from anatase showed higher adsorption efficiency of Li+ ions (qe 95.1 and 84.0 mg/g, α 34.7 and 32.9 %, respectively) compared to samples obtained from rutile (qe 75.7 and 81.2 mg/g, α 23.8 and 29.9 %, respectively). After three cycles of acid regeneration, the adsorption capacity was maintained at 40.6–47.0 mg/g for Li4Ti5O12, and at 34.8–38.4 mg/g for Li2TiO3, respectively. The hydrogen demonstration during adsorption–desorption cycles increased from 8.4 to 10.8 for Li4Ti5O12, and from 8.0 to 11.2 for Li2TiO3. Anatase Ti-containing precursor recrystallization into rutile modification and further amorphization was determined. The presented results are interesting for developing highly efficient adsorbents for Li+ ions recovery from aqueous solutions.

Regeneration of Impregnated Activated Carbon after Aging

Impregnated activated carbon (IAC) is an efficient adsorbent for the filtration of hazardous gases from the air. However, it tends to lose its efficiency after exposure to high humidity, where it adsorbs water molecules. Water adsorption causes changes in metal impregnation, resulting in a loss of adsorption efficiency for certain toxic gases, particularly gases that are adsorbed via chemisorption. Here, an innovative method was developed for the regeneration and reactivation of aged IAC. The method is based on dripping a regeneration solution composed of ammonium hydroxide and ammonium carbonate onto the aged IAC. The developed regeneration method was applied to ASZMT, a common commercially used IAC, that had undergone accelerated aging for six months. After the regeneration process, the protection capacity of the IAC against cyanogen chloride (CK) and toluene was almost fully restored to its initial value. Elemental analysis by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) showed that after the regeneration procedure, the concentrations of zinc and copper on the external surface of the IAC were decreased. This provides evidence that they were partially incorporated back into the pores. It is reasonable to believe that the developed method can be applied to IACs other than ASZMT impregnated with different kinds of materials. The implementation of this method has economic and environmental consequences. In the future, it may allow the reuse of aged IAC and even the restoration of filters.

A proposed method of solar-driven spray flash evaporation assisted by MPCM applied to solution regeneration with experimental analysis

Solution regeneration belongs to a separation and purification technology for multi-component liquid systems, which is involved in many fields such as liquid desiccant air-conditioning, desalination, and sewage treatment. Solar-driven evaporation technology has enormous energy-saving potential in solution regeneration, but it has the disadvantages of instability and slow regeneration rate. In this work, the method of solar-driven spray flash evaporation assisted by microencapsulated phase change material (MPCM) is proposed for solution regeneration. The spray flash evaporation experimental platform working with NaCl-MPCM suspension is constructed, and the spray characteristics and heat and mass transfer characteristics of NaCl-MPCM suspension are examined under different operating parameters. The results show that the addition of MPCM to the solution can significantly improve its equivalent specific heat capacity, which mitigates dispersed and discontinuous defects of solar energy. Furthermore, it can effectively reduce the severe temperature drop of the solution during the flash evaporation process, which ensures a high driving potential difference between the solution and flash evaporation environment. It is worth mentioning that under the same operating conditions, the regeneration amount per unit mass flow rate of the NaCl-MPCM suspension (wMPCM = 10 wt%) is 24.8 g/kg, which is about 19 % higher than that of the NaCl solution. Additionally, the flash performance of the NaCl-MPCM suspension can be further improved by reducing the initial fluid velocity at the nozzle or the flash evaporation pressure. This study aims to provide guidance for the efficient utilization of solar-driven flash evaporation assisted by MPCM.

Sustainable mainstream deammonification by ion exchange and bioregeneration via partial nitritation/anammox

The partial nitritation and anammox (PN/A) process has gained popularity for the treatment of nitrogen removal in wastewater due to significant energy savings and its potentially much lower CO2 footprint. However, the treatment of mainstream municipal wastewater by PN/A has been limited mainly due to its unsuitable composition. In this research, we apply ion exchange using a zeolite column to selectively remove and concentrate ammonium from mainstream municipal wastewater. After an absorption phase, the ion exchange column is regenerated using a brine solution. The ammonium rich brine is “bioregenerated” in a PN/A reactor where ammonium is converted to nitrogen gas allowing the brine to be reused in another cycle of ion exchange regeneration. To successfully remove ammonium from the spent brine, anammox and ammonia oxidizing bacteria (AOB) were first cultivated in separate reactors under hypersaline conditions (4.0 %) and later combined in a single PN/A reactor. After continuous operation with sea water, the PN/A reactor treated recirculating brine from the ion exchange column for 48 cycles of ammonium absorption and bioregeneration with minimal blowdown. The various cations of the regenerant solution were stable except for calcium that reached very high values upwards of 3000 mg/L as Ca2+ and finally caused PN/A reactor failure due to mineral precipitation. The buildup of high concentrations of calcium in the regenerant was addressed in two ways: 1) 20 % regenerant replacement per cycle, and 2) precipitation of CaCO3 via the addition of sodium carbonate. Both methods were applied to 30 absorption and bioregeneration cycles each and shown to be effective in keeping calcium concentrations from accumulating in the regenerant allowing for stable PN/A reactor operation.