Sorbent Regeneration Research Articles

BioLogic-HD™ and the problem of being (way) too far ahead of the market.

In the 1980s, I led a team to build a hemodialysis machine with sorbent regeneration of dialysate, ultrafiltration control, and single-needle access. The BioLogic-HD™ was perfectly suited for home hemodialysis, but not for in-center or acute dialysis. The home dialysis market in the United States was decimated by HCFA's decision in 1987 to stop paying for home helpers. As a result, our Venture Capital partners stopped supporting our small company, and the BioLogic-HD was never marketed. There is criticism of nephrologists for the lack of innovation in dialysis, but the major problem has been the commercialization of new dialysis technology.

Regeneration of Ion-Exchange Resins and Granular Activated Carbon with the Sonochemical Technique for Enabling Adsorption of Aqueous Per- and Polyfluoroalkyl Substances

Regeneration of adsorbents for reuse is crucial for reducing operating costs and maintaining sustainable systems. Few researchers have studied the regeneration of sorbents without using chemical solvents or appropriate methods. The purpose of this study was to evaluate the feasibility of the sonochemical technique (ST) for the regeneration of granular activated carbon (GAC), a mixed cation and anion resin (DOWEX MB-50), and an anion resin (IRA910) for the removal of per- and polyfluoroalkyl substances (PFAS). The ST was performed at 120 kW, and the power density was 250 W L−1 for 30 min. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to examine physicochemical properties of the spent adsorbents. The removal efficiency of the spent adsorbent regeneration occurred in the following order: DOWEX > GAC > IRA910. As the PFAS-adsorbed adsorbents disappeared in the spectrum, the FTIR results showed the existence of a sulfonic group that is similar to the peaks of virgin sorbents. However, this method affected the morphology of GAC and IRA910 but not DOWEX MB-50. Consequently, the ST is a potential alternative to chemical regeneration for DOWEX MB-50 resins. It is also a potential method for an eco-friendly approach to regenerate PFAS-adsorbed materials.

Studies on biosorbent developed from Rohu fish scales waste for defluoridation of water

ABSTRACT Development of waste-derived biosorbent for fluoride reduction is gaining wider interest to achieve sustainable and cost-effective water treatment. Biosorbent from Rohu fish scales waste produced from the fish market is developed for defluoridation of water. The morphological characteristics of the sorbent surface were analysed by BET, SEM, and EDAX analysis. Sorption experiments were performed in batch mode to estimate the equilibrium, kinetic and thermodynamic parameters. The equilibrium analysis indicates the sorption capacity increases linearly with the concentration of adsorbate ions and follows Freundlich isotherm. Fluoride uptake capacity of 2.972 mg/g with maximum fluoride removal of 92.12% was obtained at optimum values of process parameters: adsorbate initial concentration of 5 mg/L, pH 3, agitation rate of 150 rpm, mixing period of 90 min, temperature 303 K, and dose of 6 g/L. The E value (2.236 kJ/mol) obtained from the DR isotherm suggests the physisorption mechanism for fluoride sorption. The kinetic study indicates that fluoride sorption follows the second-order kinetic model. Thermodynamic parameters ∆H = −14.72 kJ/mol and ∆S = 0.049 kJ/mol which indicates the spontaneous and exothermic sorption nature of adsorption for fluoride reduction using fish scales sorbent. The reuse and regeneration of the exhausted Rohu fish scales sorbent was performed with 0.1 N NaOH to explore the possibility of reuse and found that it could be effectively reused up to six cycles with about 80% regeneration. The study to check practical applicability of defluoridation of field water using Rohu fish scales adsorbent indicates the adsorbent significantly reduced the fluoride.

Regenerable Sorbent Pellets for the Removal of Dilute H2S from Claus Process Tail Gas

The Claus process is the most important sour gas sweetening process to recover elemental sulfur from H2S, which is present in raw natural gas and byproduct gases from crude oil refineries. However, current methods for treating the tail gas of the Claus process are expensive and often not environmentally friendly. Various sorbents have been reported for H2S capture, but few reports focus on the pellet design, formation, and testing. In this study, we developed a pelletization method to prepare sorbent pellets with high sulfur capacity and good regenerability for the removal of dilute H2S from Claus process tail gas. The sorbent pellets consisted of mixed metal oxides of Cu, Mg, and Al with fumed silica as the binder and were characterized using various techniques, including X-ray and electron diffraction, N2 sorption, and scanning and transmission electron microscopy. The H2S sorption capacity was evaluated by breakthrough experiments at 150 °C in a gas stream consisting of 100 ppm of H2S in N2. The optimized sorbent pellets gave a stable breakthrough sulfur capacity of ∼5 mmol/g over three cycles of sulfidation and regeneration. They exhibited an average radial crush strength of 154 ± 40 N.

Ce-doping CuO/HZSM-5 as a regenerable sorbent for Adsorption–Oxidation removal of PH3 at low temperature

• Ce-doping Cu/HZSM-5 sorbents were synthesized and used for the removal of PH 3 . • Ce-doping can significantly enhance the adsorption capacity of the Cu/HZSM-5 sorbent. • The interaction between Ce and CuO improves the sorbent physicochemical properties. • The formation of phosphate/phosphide species resulted in the deactivation of sorbent. • The PH 3 capacity was preserved after three times thermal regeneration. A series Ce m Cu n O x /HZSM-5 sorbents were introduced to remove PH 3 in low-temperature and low-oxygen environments. The effects of copper loading and cerium doping on the adsorption–oxidation performance of the sorbents were investigated. Experimental results showed that doping with 1 wt% of cerium (Ce 1 Cu 30 O X /HZSM-5) could significantly improve the performance of the sorbent. The PH 3 breakthrough capacity was identified as 114.36 mg(PH 3 )•g sorbent -1 . In addition, after three thermal regeneration cycles, the sorbent still has ideal performance. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) analyses exhibited that CuO was the main active species, and Ce-doping can increase the chemisorption oxygen on the surface of the sorbent. BET results demonstrated that the introduction of cerium could improve the specific surface area and pore volume of sorbent. Hydrogen temperature-programmed reduction (H 2 -TPR) and scanning electron microscope (SEM-EDS) indicated that cerium species played an important role in uniformly dispersing copper species on the HZSM-5 surface and improving the oxidation performance of sorbent. Moreover, the reaction products and mechanisms were also investigated by XRD, XPS, and in-situ FTIR spectra. The results indicated that the consumption of CuO and the accumulation of phosphorus species (e.g., P, P 2 O 5 , and Cu 3 P) on the surface and inner pores of the sorbent were the primary reasons for the deactivation of the sorbent.

Regeneration of modified potassium carbonate with monoethanolamine sorbent supported on gamma-alumina in CO2 capture

An increase in power demand is one of the key reasons for the global warming problems due to the increase of greenhouse gas emissions. Carbon dioxide (CO2) is the main greenhouse gas emitted into the atmosphere. CO2 capture technology becomes an alternative solution to reduce CO2 emissions. There are many processes for CO2 capture technology. Among these, CO2 adsorption using solid sorbent has been wildly received attention. Most of the study was focused on the adsorption performance of solid sorbent. However, only a few studies were focusing on the regeneration of solid sorbent. This study investigated the effects of regeneration temperature and pressure on the regeneration rate of non-modified and modified K2CO3/γ-Al2O3 with monoethanolamine (MEA). The results showed that an increase in regeneration temperature and a decrease in regeneration pressure enhanced the regeneration rate of non-modified and modified K2CO3/γ-Al2O3. Furthermore, the experimental data of the regeneration rate was fitted to Avrami’s fractional-order model for further use in other applications.

Techno-economic assessment of an industrial carbon capture hub sharing a cement rotary kiln as sorbent regenerator

The concept of CCS cluster brings together multiple CO2 industrial emitters using shared capture and/or transportation infrastructure and offers several advantages for network partners compared with point-to-point individual projects. It reduces costs for CCS, and enables CO2 capture from small volume industrial facilities. The proposed concept connects a cluster of industrial sites with significant heat demands with a cement plant through the implementation of a Ca-looping CCS system. This system treats the flue gas from all the industrial emitters in independent boiler/carbonators while uses the kiln furnace as calciner for the cement and the capture plant. The carbonator reactors located in each one of the industry sites are fed by CaO from the cement plant to capture the CO2 content of their own flue gas. After carbonation reaction, the exhaust sorbent is transported back to the cement plant for regeneration in the kiln furnace. The aim of this work is to analyse the techno-economic feasibility of the proposed Ca-looping CCS cluster. The economic assessment, assuming 20 €/ton CaO and carbon market 30 €/ton CO2 points out the feasibility of this kind of centralized carbon capture system to handle the carbon from small emitters. Results show that the operating costs of small companies that use coal or natural gas reduce from 21.3 M€ to 18.8 M€ or from 25.5 to 23.0 M€. For the cement industry this income lessens its operating costs 1.9 M€ lower than a reference situation where CCS is only implemented in cement plant.

Techno-economic analysis of a 660 MWe supercritical coal power plant in India retrofitted with calcium looping (CaL) based CO2 capture system

The current study deals with techno-economic analysis of a 660 MWe supercritical coal powerplant in India retrofitted with calcium looping (CaL) based CO2 capture system. Process simulation and thermodynamic analysis are performed using Aspen Plus software, followed by a detailed economic analysis. Performance parameters of calcium looping system are evaluated for Indian high ash (HA) coal as fuel for sorbent regeneration, followed by sensitivity analysis, then compared on a techno-economic basis with different fuel varieties such as South African coal, woody biomass, rice husk and also with other CCS technologies such as MEA and Oxycombustion. Among different fuel varieties, using South African coal results in lowest energy penalty (6.14% points), using biomass based fuels leads to negative emissions and low CO2 avoided cost, using Indian HA coal results in lowest LCOE (93.7 €/MWhnet). Energy penalty of CaL system (8.63% points) is lower than MEA (9.32% points), but slightly higher than Oxycombustion (8.04% points). However, net power output of CaL system (∼870 MWe) is 45% more than existing powerplant (∼601 MWe) and 94% and 81% more than MEA (∼449 MWe) and Oxycombustion (∼482 MWe). Comparison of CCS technologies for same net power output (870 MWe) clearly shows that CaL has the lowest LCOE and CO2 avoided cost. Existing coal power plants in India (having space availability), if retrofitted with calcium looping could achieve the twin goals of decarbonisation as well as an increase in electricity generation capacity. Hence, the calcium looping technology should be explored in detail for further technology development.

CO2 Separation from Flue Gases by Adsorption

This paper deals with gas separation by adsorption processes. The key objective is to investigate the adsorption suitability for Post-combustion Carbon Dioxide (CO2) Capture (PCC). Adsorption is a promising technology suitable for a high volume of diluted gas processing. Unlike commercialised amine-based absorption processes, adsorption seems to require less energy for sorbent regeneration and extends the sorbent lifetime. Two common industrial methods utilizing a difference in adsorption equilibrium of the gas components were investigated: 1) Pressure Swing Adsorption (PSA) including Vacuum Swing Adsorption (VSA), 2) Temperature Swing Adsorption (TSA). A comparison of their energy consumption, suitability for industrial use with consideration of Carbon Capture and Storage standards is evaluated. A complex mathematical model for the adsorption step of the fixed bed adsorber was proposed and solved by the structural programming. Three adsorbent materials: Mg-MOF-74, UTSA-16, and Zeolite 13X were evaluated based on their CO2 adsorption capacity, selectivity, and market availability. Zeolite 13X was further explored. As a benchmark case, a medium-sized natural gas cogeneration unit was used to study the potential of VSA unit. The lower limit of CO2 capture efficiency in simulations was 75 %. The results presented in this paper suggest that adsorption can be a feasible CO2 capture solution for a low-carbon emission power generation technologies. Optimal parameters for the adsorption step and column configuration are proposed.

Unraveling the Role of Metal Oxide Catalysts in the CO2 Desorption Process from Nonaqueous Sorbents: An Experimental Study Carried out with 13C NMR

The CO2 desorption process from a CO2-saturated nonaqueous sorbent, 2-(2-aminoethoxy)ethanol (DGA) in diethylene glycol monomethyl ether (DEGMME), was investigated in the absence and presence of four different metal oxides, namely, V2O5, TiO2, WO3, and ZnO, aiming at identifying acid catalysts with the potential to reduce the energy demand for sorbent regeneration. The desorption performances of the DGA-DEGMME solutions with and without catalysts were evaluated in terms of CO2 desorption rate, overall CO2 desorbed, and thermal energy consumption. The desorption mechanism was understood by the 13C NMR speciation study of the solutions during the regeneration experiments. As a result, metal oxide catalysts, depending on the number and types of acidic sites on their surface, can accelerate the carbamate breakdown and the subsequent CO2 release. In particular, WO3 and TiO2 can be considered good candidates for implementation in CO2 capture processes with nonaqueous sorbents, as they greatly improved the desorption performance, and their structures remain unchanged before and after use. The combination of nonaqueous sorbents with catalysts, here reported for the first time, provides an effective strategy that could inspire the design of advanced sorbents for energy-efficient CO2 capture.

Investigation of dye removal ability and reusability of green and sustainable silica and carbon-silica hybrid aerogels prepared from paddy waste ash

In this study, the paddy waste ash (PA) was utilized for producing carbon-silica hybrid (PCS) and silica (PS) aerogels. X-ray fluorescence (XRF) spectrometer analysis revealed a high silica content in PA. Crystalline SiO2-cristobalite structure was observed in the X-ray diffraction (XRD) patterns of PA. As expected, the PCS and PS samples exhibited an amorphous SiO2 phase. The pore enlargement and structural improvement after aerogel synthesis were determined using a N2 adsorption-desorption analysis. The specific surface area of the PCS and PS samples were found to be 519 and 652 m2/g, respectively. From the zeta potential results, the points of zero charge (pHPZC) of the samples were found below “2” except for the PCS sample (pHPZC = 2.08). In the first stage of the Remazol Turquoise GN (RTGN) adsorption experiments, the effect of initial pH (2–8) was examined for PA, PCS, and PS sorbents. The highest dye removal value of the PCS sorbent was 61% at pH = 2, while this value was 17.9% and 21.4% for PS and PA sorbents, respectively. The removal percentage curve exhibited a similar trend to the zeta potential curve of the samples. In the experiments conducted with different amounts of sorbents, the dye removal percentage increased with increasing amounts of sorbents. The experimental results and thermodynamic calculations showed that the RTGN adsorption onto PCS was an endothermic process. Pseudo-first order, pseudo-second order and intra-particle diffusion equations were applied to determine the adsorption kinetics of RTGN onto PCS, and it was found that the experimental data was well-fitted to the pseudo-second order kinetic model. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption isotherm models were used to define the adsorption mechanism of RTGN onto PCS. The Freundlich and Langmuir isotherm models were in agreement with our experimental data and it was concluded that RTGN adsorption on PCS surface occurred both as single layer and multi-layer, as well as took place on heterogeneous and homogeneous surfaces. Characterization analyses were conducted for the PCS sorbent after use to understand the structural changes after dye removal. The regeneration and reusability of the PCS sorbent were investigated and it was found that it preserved its initial removal ability by about 95% after four cycles. The dye removal percentage of PCS decreased by 28% after five cycles.

Development of an ammonia production method for carbon-free energy generation

Ammonia has great prospects in the context of the transition to carbon-free energy. It can be used as fuel in gas turbines, fuel cells, internal combustion engines, and burned together with coal. However, industrial production of ammonia is based on the Haber-Bosh process, which involves the use of natural gas and coal, which, in this case, does not make it really carbon-free. This study proposes a method to produce ammonia, which is environmentally friendly and does not require the use of fossil fuels. It is based on the approach to adjusting the concentration of ammonium nitrogen in a biogas reactor and implies the sorption of ammonia from the gas phase with a solution of monoammonium phosphate, obtaining diammonium phosphate, and subsequently heating it with the release of ammonia. The factors influencing the extraction of ammonia from waste have been considered, as well as the influence of temperature on the release of ammonia from the solution of diammonium phosphate; the energy efficiency of the method has been assessed. With increasing temperature, the degree of ammonia and the degree of sorbent regeneration increased. Under laboratory conditions, 111 J/g of ammonia energy was spent. The higher the concentration of (NH4)2HPO4 in the solution, the less energy is required to obtain a unit of ammonia mass. The total amount of ammonia released varies depending on the temperature. Sorbent regeneration can be carried out using thermal energy obtained at a cogeneration plant. The possibility of using this method to produce ammonia at an industrial scale has been estimated by analyzing the ways of ammonia utilization as a fuel. The potential for ammonia production in the main livestock industries in Europe and the United States is up to 11,482,651.15 and 11,582,169.5 tons per year, respectively. Applying this solution also makes it possible to improve the efficiency of biogas production from waste with high nitrogen content. The proposed method of ammonia production could potentially contribute to the development of carbon-free energy

Thermal behavior of Cu-Mg-Al-Ba/Sr bifunctional composites during chemical looping combustion and HCl adsorption of MSW syngas

Mg-Al-supported composites of CuO Oxygen carrier (OC) and Ba/Sr sorbent synthesized by mechanical mixing were used for three-stage process of MSW syngas chemical looping Combustion and HCl adsorption (CLCA). The syngas combustion and HCl adsorption efficiencies as well as thermal behavior of the composites were investigated. It was found that the composites exhibited great reactivity and stability during cyclic CLCA process. The Ba/Sr sorbent slightly influenced the redox ability of OC owing to the presence of Cu2MgO3, but exhibited no impact on the MSW syngas combustion, achieving nearly full combustion during 20 cycles. Regarding to the conditions for sorbent regeneration, higher H2O content and temperature facilitated sorbent regeneration, allowing better HCl adsorption at fuel reaction stage. The sorbent regeneration conditions were optimized at 60 vol% H2O and 900 °C. Ba-loading composite exhibited better HCl adsorption performance than the Sr-loading during 20 CLCA cycles maintaining 25–35 ppmv HCl in flue gas because of its better regeneration efficiency (∼95%). The CuO/Cu migration to the surface enhanced the stability on mechanical strength, elemental composition and redox ability without appearing significant agglomeration during 20 cycles, maintaining the stability in the reactivity with MSW syngas for long-term operation.

Hyper-crosslinked tetraphenylborate as a regenerable sorbent for Cs+ sequestration in aqueous media through cation-π interactions

Practical adsorbents that could efficiently collect radioactive Cesium (Cs+) are critically important in achieving proper management and treatment measures for nuclear wastes. Herein, a hyper-crosslinked tetraphenylborate-based adsorbent (TPB-X) was prepared by reacting TPB anions as Cs+ binding sites with dimethoxymethane (DMM) as crosslinker. The most efficient TPB-X synthesis was attained at 1:4 TPB/DMM mole ratio with sorbent yield of 81.75%. Various techniques such as FTIR, TGA-DTG, N2 adsorption/desorption and SEM-EDS reveal that TPB-X is a water-insoluble, thermally stable and highly porous granular sorbent. Its hierarchical pore structure explains its very high BET surface area (1030 m2 g−1). Sequestration of Cs+ by TPB-X involves its exchange with H+ followed by its binding with the phenyl rings of TPB through cation-π interactions. The Cs+ adsorption in TPB-X is endothermic and spontaneous, which adheres to the Hill isotherm model (qm = 140.58 mg g−1) and follows pseudo-second order kinetics (k2 = 0.063 g mg−1 h−1). Calculations from the density functional theory reveal that the binding of TPB anion is strongest for Cs+. Thus, TPB-X was able to selectively capture Cs+ in simulated surface water containing Na+, K+, Mg2+, and Ca2+ and in HLLW containing Na+, Rb+, Sr2+, and Ba2+. Hyper-crosslinking was found beneficial in rendering TPB-X reusable as the sorbent was easily retrieved from the feed after Cs+ capture and was able to withstand the acid treatment for its regeneration. TPB-X exhibited consistent performance with no sign of chemical or physical deterioration. TPB-X offers a practical approach in handling Cs+ contaminated streams as it can be repeatedly used to enrich Cs+ in smaller volume of media, which can then be purified for Cs+ reuse or stored for long-term natural Cs+ decay process.

TECHNOLOGY OF COMPLEX SORPTION TREATMENT OF INDUSTRIAL WASTEWATER FROM SULPHIDE AND COPPER(II)–IONES

Complex processing of industrial waste of individual industries, including wastewater treatment, containing sulfur anions and cations of heavy metals, in order to obtain both purified water and finished industrial products is an urgent task for today. The possibility of efficient use of regenerated mixed sorbent (AC+K), containing activated carbon (AC) and diatomaceous earth (K), for wastewater treatment of certain technological processes of chemical (petrochemical) industry and galvanic industries has been shown. The sorbent with the removed contaminants was offered to be utilized as a part of plastic lubricants of special purpose. The technological process of complex sorption treatment of industrial wastewater from sulfide and copper (II) ions includes the following main stages: sorbent regeneration; purification of sulfide-alkaline solutions; purification of washing waters of galvanic productions; obtaining plastic oils. The basic technological scheme of the site of regeneration of the spent mixed sorbent (AC+K) and purification of water-sugar solutions from organic impurities was developed. The material balance of regeneration of the spent mixed sorbent was calculated. The basic technological scheme of the site of combined treatment of industrial wastewater from sulfide and copper (II) ions, regeneration of spent industrial oils with regenerated sorbent (AC+K) and production of plastic oils has been developed. It was shown that the technology of complex sorption wastewater treatment is based on the most common technological processes - heating, cooling, adsorption and filtration and does not require complex schemes of automatic process control, and chemical equipment is typical for chemical enterprises in Ukraine. The economic effect of production of special purpose plastic oils was calculated.

Outstanding performance of sulfurated titanomaghemite (Fe2TiO5) for hexavalent chromium removal: Sulfuration promotion mechanism and its application in chromium resource recovery

A lot of magnetic sorbents have been developed to meet the current demand for removing Cr (VI) from wastewater. However, the application of magnetic sorbents remains restricted by the unsatisfactory Cr (VI) removal efficiency, sorbent regeneration, and safe disposition of adsorbed Cr species. In this study, magnetic titanomaghemite (Fe2TiO5) was sulfurated with gaseous H2S to improve its Cr (VI) removal efficiency. Sulfuration significantly improved the Cr (VI) removal efficiency of Fe2TiO5 from 3%–14% to 27%–82% at pH 4–10 due to drastically increased the electrostatic adsorption of Cr (VI) and heterogeneous reduction of adsorbed Cr (VI) to Cr (III). Furthermore, the sulfurated Fe2TiO5 recovered using magnetic separation can be regenerated by re-sulfuration without degrading the Cr (VI) removal efficiency, therefore, sulfurated Fe2TiO5 can be recycled for Cr (VI) removal after the regeneration. Moreover, Cr (VI) in aqueous solution can be enriched on sulfurated Fe2TiO5 after multiple adsorptions in the form of Cr2O3 in a content of more than 30% what can be considered as a source of chrome ore. Therefore, sulfurated Fe2TiO5 may be a promising, low-cost, and environment-friendly sorbent for Cr recovery as a co-benefit of Cr (VI) removal from wastewater.

High-Capacity Regenerable H2S Sorbent for Reducing Sulfur Emissions

High-Capacity Regenerable H₂S Sorbent for Reducing Sulfur Emissions

Chromatographic separation of mannitol from mixtures of other carbohydrates in aqueous solutions

The isolation of mannitol from natural sources, e.g. from plant extracts or broths, requires considerable time and effort. The separation of mannitol from aqueous solutions containing also glucose, fructose, and sucrose was tested using discontinuous preparative anion- and cation-exchange chromatography. The suitability of the application in the separation of carbohydrates and especially mannitol was tested under various conditions and using three different types of ion-exchangers. The effect of sorbent regeneration and modification on the separation was also examined using different concentrations and volumes of chemical agents. The fractions collected after the discontinuous chromatography were analysed on the content of mannitol by the high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method. The successful isolation of pure mannitol fraction, using water as a mobile phase and a combination of sodium chloride and hydroxide for sorbent regeneration, was achieved only on anion-exchange chromatography.

Enhanced mercury removal performance of Cu-Fe binary oxide sorbents modified by non-thermal plasma

In this work, magnetic Cu-Fe binary oxide (CF) sorbents synthesized by sol − gel method are modified by oxygen non-thermal plasma for efficient removal of elemental mercury (Hg0) from coal-fired flue gas. Sample characterization indicates that plasma treatment has very little impact on the physical properties, magnetization characteristics, and crystalline phases of CF sorbents. But the content of Fe3+, Cu2+, and lattice oxygen in CF sorbents are significantly improved after plasma treatment. Mercury adsorption experiments suggest that the modified sorbents show higher Hg0 removal efficiency in comparison with raw sorbents, and longer treatment time leads to higher Hg0 removal efficiency. The effect of plasma discharge power (32–96 VA), discharge atmosphere (N2, air, 50% N2 + 50% O2, and O2), and reaction temperature (50–350 °C) on mercury removal performance are also explored in a fixed-bed reactor. The presence of O2, NO, and HCl promote Hg0 removal. SO2 and H2O suppress Hg0 removal, but O2 addition can obviously weaken such inhibitory effects. Both experimental results and kinetic model indicate that chemisorption is the decisive factor for Hg0 removal over CF sorbents. Moreover, the mechanism of Hg0 removal over the modified CF sorbents is also investigated. The results indicate that Fe2O3 and CuO serving as active sites are greatly consumed in Hg0 removal process. The multiple regeneration cycles testify that the combination of thermal desorption and non-thermal plasma treatment can realize the efficient regeneration of CF sorbents.

Kinetic study and modeling on the regeneration of Li4SiO4-based sorbents for high-temperature CO2 capture

Li4SiO4 is acknowledged as a promising sorbent candidate in high-temperature CO2 adsorption. However, reaction kinetics for the regeneration process of Li4SiO4, especially its dependence on CO2 pressure is lack of understanding. This work designed and carried out a series of isothermal tests on the regeneration of pure Li4SiO4 and K-Li4SiO4 under CO2 partial pressure of 0–0.5 atm and temperature of 625–725 °C. For the first time, the expression of (Peq − PCO2)n is introduced into the regeneration rate equation so as to reveal its dependence on CO2 pressure. The reaction order (n) is found to grade according to the value of (Peq − PCO2), and the apparent activation energy is calculated as 284.42 kJ•mol−1 and 146.31 kJ•mol−1 for the regeneration of Li4SiO4 and K-Li4SiO4, respectively. Furthermore, this work proposes that power law model with m = 4/3 is the most probable mechanism function for the regeneration of Li4SiO4-based sorbents.