Ammonia Sorption Research Articles

TiO2 promoted alcohol dehydrations on the Wells-Dawson type heteropolyacids

The catalytic dehydrations of methanol and n-butanol on strongly acidic solids have been tested in two types of microreactors in the gas phase between 80 – 240 ºC. For the methanol transformation to dimethyl ether, the conversion was evaluated in situ with an innovative use of the FTIR spectroscopy in batch microreactor. The same catalysts were used for the conversion of n-butanol to butenes and n-butyl-ether under similar conditions, determined using a flow microreactor with the conventional gas chromatography downstream analysis. The catalysts included the Wells-Dawson type heteropolyacids, H6P2W18O62 and H6P2Mo18O62, supported on TiO2 and/or BN. The activity orders obtained in those methods were compared to that obtained by the ammonia sorption using the gas-flow through microcalorimeter at 150 ºC. The significant effect of TiO2 and BN supports in the methanol and butanol dehydrations makes the TiO2 and BN-supported Well-Dawson type heteropolyacids potentially relevant for industrial transformations of biomass derived feedstock.

Biochar as ammonia exchange biofilm carrier for enhanced aerobic nitrification in activated sludge

The effects of biochar on aerobic nitrification in activated sludge were investigated in sequencing batch reactors. Biochar amended reactors exhibited 87–94 % lower ammonia in effluent and 16–71 % greater removal of total Kjeldahl nitrogen compared to control reactors. Quantitative qPCR analyses revealed that the relative abundance of ammonia oxidizing bacteria (AOB, amoA/16S rRNA genes) was greater in biochar than in control reactors. AOB were enriched on biochar surfaces, with biochar particles having up to 12.1 times greater relative abundance of AOB compared to suspended biomass. Biochar’s maximum ammonia sorption capacity of 4.4 mg N/g at pH 7 decreased with decreasing pH, however a pH-sensitive fluorescent probe was used to show that biofilms growing on biochar surfaces maintain a median pH of > 6.7 despite reactor acidification by nitrification. Microbial colonization of biochar in activated sludge creates a pH-sheltered environment that sustains biochar’s ammonia sorption capacity, resulting in enrichment of AOB on biochar particles and improved nitrification.

Application and Challenge of Metal/Covalent Organic Frameworks in Ammonia Sorption and Separation.

As both a critical chemical feedstock and an environmental pollutant, the production and utilization of ammonia (NH3) are accompanied by the progress of social civilization. In recent years, research on metal/covalent organic framework materials as NH3 adsorbents has attracted increasing attention due to their high porosity, versatile architecture and tunable functionality. This review was organized to highlight the recent advancement of MOF/COF materials for NH3 sorption, which successively presented the key properties of solid adsorbents and summarized the strategies along with their mechanisms for enhancing NH3 adsorption. In addition, perspectives and outlook regarding the future development of MOF/COF-based NH3 adsorbents were outlined to meet the requirements of practical applications under various condition.

Activated Carbons for Removing Ammonia from Piggery Vent Air: A Promising Tool for Mitigating the Environmental Impact of Large-Scale Pig Breeding

Unsustainable pig breeding is a great threat to the environment. Ammonia is one of the main pollutants emitted in piggery vent air. This work is a comparative survey that presents the findings on the effectiveness of ammonia adsorption from air using various activated carbons (ACs). Detailed consideration is given to the effects of (i) type of raw material (wood char, wood pellet, and commercial lignite-based char), (ii) preparation method (CO2, steam, and KOH activation), and (iii) activation conditions (temperature and KOH/char ratio), on the porous structure of ACs and their ammonia sorption capacity and reversibility. Response surface methodology and genetic algorithm were used to find optimum KOH activation conditions. Economic analyses of AC production were performed using process modeling in Aspen software. It was found that ACs obtained from wood char in KOH activation show a maximum ammonia capacity of 397 g/kg, which is at least 2.5-fold higher than that reached on ACs from physical activation. A lower activation temperature (<750 °C) and a higher KOH/char ratio (>3) were preferred for effective adsorption, regardless of the type of feedstock. High sorption reversibility was achieved (87–96%). This makes the obtained sorbents promising sorbents for ammonia removal from piggery vent air with potential subsequent application as nitrogen-enriched biochar for crop fertilization. Thus, it facilitates sustainable pig breeding.

Ammonia permeation and plasticization of glassy polymeric membranes

Ammonia (NH3) is a vital industrial chemical and a potential clean fuel, whose production is increasing globally. The permeation of ammonia through glassy polymeric membranes demonstrates considerable variability, due to hydrogen bonding with both the polymer and residual water. This study reveals the underlying mechanisms for ammonia permeability within membranes, which is strongly correlated with the presence of water and the polymer's chemistry. Three polymers with varying water/ammonia affinity were studied: poly (vinyl alcohol) (PVA), polysulfone (PSU), and Teflon AF 1600. Ammonia was found to readily plasticize PVA, with sorption isotherms that follow Henry's law at conditions below the nominal glass transition temperature. Residual water within the PVA membranes increased ammonia permeability by an order of magnitude greater than that observed for well-dried PVA, due to water-induced swelling. PSU, being hydrophobic, was unaffected by residual water, though ammonia permeability was clearly time-dependent with a 50 % reduction over 4 days. This was attributed to ammonia clustering within the ammonia phobic PSU, which resulted in pore-blocking. The superhydrophobic Teflon AF 1600 membrane demonstrated the same time dependent permeability behaviour, but at a much faster timescale of minutes rather than days. It is suggested that this relates to the rate of formation of ammonia clusters, which is dependent on the degree of ammonia sorption within the polymer.

Aquatic weed Eichhornia crassipes as sustainable feedstocks for biochar production: A potential of ammonium adsorption and kinetic models

The rapid emergence of unique types of pollutants is of worldwide concern owing to their deleterious effects on living beings. Mitigating pollution in the way of sustainability is the need of the hour to protect the existing environment from degradation. In this regard, eco-friendly biochar was prepared from the intact plant of Eichhornia crassipes (water hyacinth) without neglecting the roots, stems, leaves, and flowers and assessed for its ammonium removal efficiency in the study. Twelve biochars of two categories, viz., treated and normal, were produced under two different pyrolysis temperatures of 300 °C and 500 °C and three residence times of 30, 45, and 60 min. The adsorption experiments were conducted as batch studies in triplicate to examine the impacts of multiple adsorption-inducing factors in biochar. The maximum ammonium removal efficiency of about 83% was shown by the alkali-activated biochar produced at a higher temperature of 500 °C with a longer residence time of 60 min. The biochar showing higher ammonium adsorption was characterized by Scanning Electron Microscopy and Fourier Transform Infra-Red spectroscopy, which revealed the increased number of pores and the presence of C–O, OH, and CO groups that altogether aided the adsorption process. The kinetic study conducted with contact times of 30, 60, and 90 min showed that the linear regression values were >0.999 for the pseudo-second-order kinetic model, which revealed that the ammonia sorption of Eichhornia biochars followed a second-order mechanism of chemisorption. Synthesized biochar has shown significant efficacy in ammonia adsorption, making it worthwhile in applications where ammonia removal is necessary, particularly in wastewater treatment besides agriculture and air purification.

Experimental study of the new composite materials for thermochemical energy storage

Thermochemical energy storage (TCES) is a promising technology to support the world's initiatives to reduce CO2 emissions and limit global warming. In this paper, we have synthesized and characterized a new three-component composite materials consisting of a mixture of calcium chloride and iron powder confined inside the expanded vermiculite. The new approaches of studying composite sorbents of ammonia using a gas flow-through microcalorimetry proposed in this work. The energetics of adsorption as a function of ammonia uptake was measured at room temperature (RT), 106 and 150 °C. The enthalpy of NH3 sorption in eight cycles tested ranged from 12.2 to 39.1 kJ mol−1. The strength of ammonia sorption on composite surface was characterized by TPD (Temperature Programmed Desorption). Based on the NH3-TPD profiles of composites it was found that the high-temperature desorption peaks of vermiculite sample shifted to lower temperature after the deposition of salt. The characterization of the composites was complemented by the laboratory analyses using XRD, WD-XRF, FTIR, TG/DTG, SEM-EDS and nitrogen sorption isotherms at −196 °C (BET method). The composite impregnated with 37 wt% of salt has the highest enthalpy and sorption capacity, thus seems to be the most promising candidates for the heat storage systems.

Study on ammonia transport and separation in Aquivion® perfluoro sulfonated acid membranes

The present study reports the results of a series of sorption and permeation tests of pure ammonia as well as nitrogen and hydrogen carried out on Aquivion C87-05 (short-side chain perfluoro sulfonic acid ionomer). Such material is indeed of interest for possible applications in sustainable processes for ammonia production, either as base material for polymer electrolyte membranes in low-temperature electrochemical ammonia synthesis or as a membrane for effective product separation.NH3, N2, and H2 permeation tests are performed at different temperatures (20, 35, and 50 °C) and both in dry and humid conditions (R.H. up to 80%), aiming to assess the influence of these parameters on the resulting permeabilities, while ammonia sorption is inspected at the same temperatures, and pressures up to near saturation conditions.Pure ammonia permeability reached outstanding values around 7000 Barrer in dry Aquivion membranes, revealing an increasing trend with upstream pressure, while it decreased with temperature. The same behavior is recorded for NH3 solubility, indicating that sorption drives the ammonia transport through the membrane.The obtained separation performances are found to be significantly better than those of other polymeric membranes proposed for the same separations, as compared to a permeability-selectivity plot.

Demonstration of long-term cyclic sorption of ammonia in modified expanded graphite-calcium chloride composites for practical applications

The long-term viability of the ammonia‑calcium chloride (NH3−CaCl2) pair in commercial adsorption refrigeration systems faces challenges due to the disintegration of calcium chloride (CaCl2) during multiple ammonia sorption cycles. To address this issue, we conducted a comprehensive study, starting from lab-scale investigations to experiments with full-scale commercial refrigeration systems. We prepared three calcium chloride–expanded graphite (CaCl2:EG/4:1) composite samples (labelled B1, B2, and B3) with varying water content (20–45% by weight), and also used a conventional CaCl2-activated carbon-white cement composite (CaCl2:AC:WC/16:4:1, sample A). The composites were coated over fin tubes wrapped around with wire mesh for this purpose. These composites were tested for structural integrity over 300 continuous cycles in a customized constant-volume single fin-tube adsorption/desorption bed. While all samples initially exhibited similar sorption capacity ∆χof≈0.6−0.7kgNH3/kgCaCl2, sample A experienced a significant deterioration of approximately 60% in capacity within 300 cycles due to agglomeration and volumetric expansion. In contrast, the EG-based samples demonstrated remarkable stability, with B3 maintaining ∆χ≈0.57kgNH3/kgCaCl2 even after 800 cycles. We applied B3 in a 2 TR adsorption refrigerator that uses biomass as fuel to demonstrate <15% cooling power attenuation even after prolonged operation over 800 cycles in practical scenarios. We believe these engineering interventions are necessary to encourage the broader adoption of ammonia-based adsorption refrigeration systems, which are a sustainable choice due to their zero global warming and ozone depletion potentials.

Ammonia sorption thermal battery with water-loaded sorbent driven by low-temperature heat source

Ammonia sorption thermal battery with water-loaded sorbent driven by low-temperature heat source

Investigation of Nonidealities through an Extended Flory–Huggins Model of Ionic Liquid Mixtures with Ammonia

The phase behavior of ionic liquids and ammonia is critical due to their application in various fields such as sorption-based heating/cooling cycles and direct ammonia capture. To date, various ionic liquids have been developed and investigated to enhance the solubility of ammonia without compromising the reversibility due to recycling concerns and various thermodynamic models have been used to correlate the experimental vapor–liquid equilibria data. Surely, high ammonia sorption capacities are required and understanding the interaction between ammonia and ionic liquids can lead to synthesizing targeted ionic liquids for ammonia. In this study, we developed an extended Flory–Huggins model on ammonia and imidazolium-based ionic liquid systems, where both combinatorial and residual terms are considered, to understand the interaction between ammonia and ionic liquids. The results showed that the nonidealities in ammonia and imidazolium-based IL mixtures are due to both entropic and enthalpic contributions. Therefore, increasing the size of the IL would not be enough to achieve higher solubilities. A deeper understanding of the molecular-level interaction between ionic liquids and ammonia can be investigated via molecular simulations.

RESPIRATORY ORGANS PROTECTION FROM THE AMMONIA ACTION

The article deals with the issues of protection of the respiratory organs from the toxic effects of ammonia, based on the research of employees of the Physical-chemical institute for environment and human protection of MES OF Ukraine and NAS of Ukraine. The physicochemical properties of ammonia and its toxicological characteristics are discussed in detail. Emergency hygienic regulations and reference levels of its concentration in the air are given, depending on the severity of possible effects. Activated carbon, the most widely used for equipping gas-absorbing cartridges of respirators and industrial gas masks, does not have the ability to selectively absorb ammonia without treatment with chemically active compounds. To enhance selectivity, activated carbon is infiltrated with d-metal salts and organic polybasic acids. An alternative to granular charcoal sorbents are ion-exchange fibrous materials or impregnated fibrous chemisorbents (IFCS), which have a significantly lower weight and breathing resistance. Impregnation was carried out with solutions of citric acid, and glycerol, sodium chloride, and ethanol were used as modifiers to achieve a uniform distribution of citric acid on the surface of the fibers and increase adhesion to them. The study of the sorption characteristics of IFCS as part of the gas-absorbing cartridge of the «Klen-K1» respirator was carried out with dry and moistened samples under dynamic conditions close to the actual operation of respiratory protection equipment: NH3 concentration in the gas-air mixture 700 mg/m3 (35 TVL), relative humidity φ = 0 ÷ 72%, linear flow rate – 5,1 sm/s. It is shown that the humidity of the gas-air mixture plays a decisive role in the efficiency of ammonia sorption, it activates the protective properties of IFCS. It has been established that gas-absorbing cartridges equipped with the developed samples of IFCS impregnated with a 40.0% solution of citric acid with the addition of 3.3% glycerol and 1.0% sodium chloride provide the normalized requirements for class K1 gas filters (ammonia) with humidity of the inhaled air ≥ 30%. The presence of «free» water provides a more complete «activation» of the specified chemisorbent for this toxicant.

Composites “lithium chloride/vermiculite” for adsorption thermal batteries: Giant acceleration of sorption dynamics

Adsorption thermal batteries have been proposed for storing heat from renewable and waste energy sources. Composites “salt in porous matrix” based on expanded vermiculite have extraordinary methanol sorption and heat storage capacities. However, their practical implementation is restricted by slow desorption, leading to low battery power. This paper aims to accelerate methanol desorption from a composite LiCl/vermiculite through its modification by an aluminum-oxygen containing additive. First, the dynamics of methanol sorption/desorption is studied for a pristine LiCl/vermiculite to reveal the factors braking sorption. Slow heterogeneous nucleation and sluggish growth of crystalline LiCl are shown to dramatically inhibit the methanol desorption from the pristine LiCl/vermiculite composite. To accelerate the nucleation, the vermiculite is modified by 2.5–8.9 wt% of aluminum-oxygen containing additive. Both pristine and modified sorbents are characterized by XRD, SEM, DSC, and BET techniques. The modification allows a giant acceleration of methanol desorption. The characteristic time corresponding to conversion 0.8 reduces by a factor of 2–12 as compared with the pristine composite. The dynamics acceleration affords fourfold increase in the specific power of the heat storage stage of adsorption thermal batteries employing the new composite. In a broader sense, the proposed approach could help accelerate the sorption of methanol, water, and ammonia on composites based on macroporous matrixes and could be advantageous for various adsorption applications.

Sulfated Zirconium Metal-Organic Frameworks as Well-Defined Supports for Enhancing Organometallic Catalysis.

Understanding heterogeneous catalysts is a challenging pursuit due to surface site nonuniformity and aperiodicity in traditionally used materials. One example is sulfated metal oxides, which function as highly active catalysts and as supports for organometallic complexes. These applications are due to traits such as acidity, ability to act as a weakly coordinating ligand, and aptitude for promoting transformations via radical cation intermediates. Research is ongoing about the structural features of sulfated metal oxides that imbue the aforementioned properties, such as sulfate geometry and coordination. To better understand these materials, metal-organic frameworks (MOFs) have been targeted as structurally defined analogues. Composed of inorganic nodes and organic linkers, MOFs possess features such as high porosity and crystallinity, which make them attractive for mechanistic studies of heterogeneous catalysts. In this work, Zr6-based MOF NU-1000 is sulfated and characterized using techniques such as single crystal X-ray diffraction in addition to diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The dynamic nature of the sulfate binding motif is found to transition from monodentate, to bidentate, to tridentate depending on the degree of hydration, as supported by density functional theory (DFT) calculations. Heightened Brønsted acidity compared to the parent MOF was observed upon sulfation and probed through trimethylphosphine oxide physisorption, ammonia sorption, in situ ammonia DRIFTS, and DFT studies. With the support structure benchmarked, an organoiridium complex was chemisorbed onto the sulfated MOF node, and the efficacy of this supported catalyst was demonstrated for stoichiometric and catalytic activation of benzene-d6 and toluene with structure-activity relationships derived.

Modeling of Gas Sorption Process by Dispersed Liquid Flow

A mathematical model of the process of gas propagation in the atmosphere and its sorption by fine flow has been developed. The use of the finite difference method in modeling allows to obtain numerical solutions of the spatial distribution of gas concentration during its deposition by a jet of arbitrary intensity and shape. The proposed method of mathematical description of the process of sorption of hazardous gases allows you to choose an arbitrary number and spatial location of nodal points that satisfy the Courant-Friedrichs-Levy condition. The developed model allows to predict the intensity of gas sorption in technological processes and in the elimination of the consequences of emergencies. The use of the developed model will increase the efficiency of emergency management and choose effective methods of sorption of hazardous gases in the atmosphere. The results of numerical calculations confirmed the efficiency of the developed model and theoretically demonstrated the effectiveness of using water curtains for the sorption of ammonia from the atmosphere. According to the simulation results, it is established that the use of fine spray jets can significantly reduce the distance of distribution of hazardous gas.

Using nitrogen-loaded biochar for soil improvement to decrease applied nitrogen and stabilize rice yield under alternate wet-dry irrigation

Nitrogen (N) loss from paddy fields is an important cause of eutrophication and yield decrease. In order to minimize the negative impact of N loss, biochar was used as a medium for the sorption of ammonia from simulated wastewater and subsequently as a N releaser in the cultivation of rice plants under the N deficiency environment during two years. The experiment was conducted in a completely randomized block design, with a conventional fertilization treatment (N1C0), 10 t/hm2 or 20 t/hm2 N-loaded biochar and 25% less N fertilizer (N3/4C1, N3/4C2), and 10 t/hm2 or 20 t/hm2 N-loaded biochar and 50% less N fertilizer (N1/2C1, N1/2C2). The NH4+-N and NO3--N concentrations in surface water, the number of rice tillers, dry matter weight, and N uptake were measured. Results showed that the adsorption efficiency of the prepared N-loaded biochar to NH4+-N was 30.8%; reducing the amount of N fertilizer coupled with N-loaded biochar application reduced the average surface water concentration of NH4+-N by 15.44–43.62% within one week after rice transplantation; it also reduced the average surface water concentration of NO3--N during the whole growth period by 18.76–25.19%. In the late rice growth stage, the average concentration of NH4+-N in surface water was shown in descending order: N3/4C2 ＞N3/4C1 ＞ N1C0＞ N1/2C2 ＞ N1/2C1. Compared with N1C0, N3/4C2 did not clearly impacted the rice tiller numbers, the dry matter weight and N uptake of rice stems, leaves and panicles. In sum, under alternate wet-dry irrigation, 20 t/hm2 N-loaded biochar purified the eutrophic water in the irrigation area and permitted N fertilizer input to be reduced by 25%, which stabilized rice yield and was conductive to improving a spatial balance of “misplaced” N resource.

High-efficiency capture of ammonia using hierarchically porous Zr-MOF nanoarchitectures under ambient conditions: Thermodynamics, kinetics, and mechanisms

Zirconium-based metal–organic frameworks (Zr-MOFs) have emerged as a promising candidate for efficiently eliminating toxic chemicals under ambient conditions. Herein, we demonstrate the remarkable ammonia capture capabilities of the hierarchically porous MOF-808 xerogel (G808) macrostructure and its amino-functionalized analogue (G808-NH2), which were constructed through a sol–gel-based strategy combined with convenient ambient pressure drying. Static isotherm measurements and dynamic breakthrough tests using engineered Zr-MOF xerogel granules were conducted to illuminate the thermodynamic and kinetic characteristics for ammonia sorption. The G808 and G808-NH2 xerogels manifest substantially higher ammonia uptake, intensified interfacial interactions, and enhanced irreversible retention toward ammonia compared with the state-of-the-art activated carbon-based materials, particularly at the low-concentration region. Moreover, these hierarchical Zr-MOF nanoarchitectures exhibit extraordinary ammonia removal performance as well as excellent environmental robustness under simulated respirator canister/protection filter circumstances, with the breakthrough capacities of G808-NH2 being individually more than two and one orders of magnitude greater than those for the pristine and metal-amine impregnated carbons. The kinetic ammonia adsorption behaviors can be well delineated by the pseudo-first-order Wheeler-Jonas model. An in-depth discussion on the ammonia sorption regime, detailing five binding patterns besides reversible physisorption with a special focus on the impacts of polar amino groups and humidity, was proposed based on multiple characterizations and Grand Canonical Monte Carlo simulation.

Strategies for the production of a stable blended fertilizer of anaerobic digestates and wood ashes

The wood ash-based treatment of anaerobic digestates is a novel technology to achieve the stabilization and improve the properties of organic amendments as slow-release fertilizers. The present work evaluated 3 strategies to optimize the blending of these materials under minimum acidification. The first strategy consisted in the titration of 2 samples of digestate and 2 samples of wood ash with 4 acids (H2SO4, HCl, HNO3, and CH3CHOHCOOH). The stability of the samples was inferred from the pH measurements and the simulations with Visual MINTEQ allowed to confirm some of the on-going phenomena. The bottom ash and the agro-waste digestate required less acid to reach the targeted pH of 5.5, which prevents ammonia volatilization, due to low reactivity of the coarse particles and the low ammoniacal nitrogen content, respectively. The calculation of the pH of zero point of charge further minimized the use of acid reagents, since the optimum pH for the treatment of the digestates could be 11.90 ± 0.50 and 12.43 ± 0.06, when employing the finer and coarser fractions of the ashes, respectively. In the second strategy tested, commercial doses of acids were applied to the digestates before the addition of the ashes. The sorption of ammonia onto the fly ash at pH 10.49 ± 0.76 was found to be key to preserve the nitrogen of the food waste digestate, while saving HCl or HNO3. The third strategy involved washing the ashes repeatedly with ultrapure milli-Q® water to remove the impurities and reach a pH closer to the zero point of charge without using acids. The removal of impurities and most reactive alkali elements (e.g. sodium and potassium) from the ashes led to approximately 5 % lower pH and higher carbon, calcium, and magnesium contents, which could enhance sorption processes upon combination of these materials with the digestates. The integration of washing the wood ashes and commercial acidification of anaerobic digestates would provide the best conditions for the preparation of stable blends. This procedure also minimizes the use of acids, which disrupts the closed-loop valorization of these materials.

Modelling and Analysis of Ammonia Sorption Reactions in Halide Salts

This work has focussed on the development of an accurate method for testing and modelling the reaction kinetics involved in ammonia-salt adsorption reactions, something not achieved consistently to date. A Large Temperature Jump (LTJ) test cell has been developed for testing ammonia-salt reactions in real machine conditions. A Large Temperature Jump (LTJ) test cell has been developed for testing ammonia-salt reactions in real machine conditions. This was used to validate a new approach to modelling the behaviour and simulate the performance of chemisorption machines. A derivation of the heat transfer and thermodynamic equations are presented, and a finite difference model described which has been validated for the adsorption and desorption reactions of ammonia into halide salts within a porous matrix. The model is implemented in a MATLAB® program. Large Temperature Jump (LTJ) tests have been conducted on manganese chloride and barium chloride to validate the model and to identify the physical parameters which characterise the dynamic performance of the sorbent. The manganese chloride and barium chloride were impregnated in expanded natural graphite (ENG) (SGL SIGRATHERM®) board. The ENG board gave rise to practicable samples (31.5 mm OD ø over ½” tube) undergoing a desorption reaction in under 250 seconds with the fluid temperature 15°C above the equilibrium temperature, an order of magnitude faster than observed elsewhere. A new test method has been developed enabling an accurate single heat of reaction to be identified due to reduced hysteresis, which is reported for barium and manganese chloride. The model has been validated using experimental data from LTJ tests of two geometric configurations in radial heat transfer: discs heated/cooled from the outside radius (‘tube-side’) and annuli heated from the inner radius (‘shell-side’). The empirical data obtained is a milestone towards designed and optimised salt generators.

Smart temperature difference management in summer desert enabled by ammonia-based resorption cycle

Diurnal temperature difference management driven by solar energy is one of the essential and attractive strategies in summer desert. However, the conventional phase-change thermal energy storage way possesses inherent drawbacks of serious heat dissipation, low heat storage efficiency, single-mode thermal energy storage, etc. Herein, we report a smart temperature difference management (STDM) strategy based on the ammonia-based resorption cycle of MnCl2@expanded natural graphite (ENG) treated with sulfuric acid and CaCl2@ENG composite sorbents for adjusting indoor diurnal temperature variation in summer desert. In midday refrigeration mode, the desorption reaction of MnCl2 and the sorption reaction of CaCl2 occurs by harvesting sunlight during the forenoon, subsequently the resorption reaction of MnCl2 taking place to discharging cooling capacity at midday. In the night heating supply mode, the resorption process of MnCl2 happens to discharging thermal energy, but the desorption process during the afternoon is similar to the forenoon. Amplifiable composite sorbents own high ammonia sorption capacity up to 0.540 g∙g−1 and 0.915 g∙g−1 contributed by strong ammonia complexation reaction. Based on these sorbents, the STDM device realizes cold and heat charging/discharging via the multistep ammonia desorption/sorption process of MnCl2 and CaCl2 composite sorbents in closed structures driven by solar energy in summer desert. Importantly, the lab-scale STDM device exhibits high heating supply performance of 213.65 kJ∙kg−1 (SHE), 49.86% (ηh), 8.2 °C (△Th), 40.67 min (th) at night and high refrigeration performance of 163.6 kJ∙kg−1 (SCE), 0.344 (COPc), 3.88 °C (△Tc), 33.5 min (tc) at midday. Our approach offers a prospective low-carbon route for efficient temperature difference management in summer desert.