Improved Thermal Conductivity of 13X/CaCl2 Composite Adsorbent by CNT Embedment

2013 ◽  
Author(s):  
K. C. Chan ◽  
Christopher Y. H. Chao
Keyword(s):  
Thermal Conductivity ◽  
Adsorption Capacity ◽  
System Performance ◽  
Cooling System ◽  
High Adsorption ◽  
Composite Adsorbent ◽  
Low Thermal Conductivity ◽  
Zeolite 13X ◽  
Composite Adsorbents ◽  
Adsorption Desorption

Adsorption cooling systems utilize the principle of adsorption to generate cooling effect. Composite adsorbents synthesized from zeolite 13X and CaCl2 have previously been shown to have a high adsorption capacity and high adsorption rate with lower desorption temperature where the adsorption capacity and adsorption rate are 420% and 122% of zeolite 13X under the same condition respectively. This results in more compact design and a lower temperature waste-heat source can be used. The system performance is, however, limited by the low thermal conductivity of the 13X/CaCl2 composite adsorbent which is common for many adsorbents. Due to the low thermal conductivity of the adsorbent, poor heat transfer and slow temperature change in the adsorbent bed lead to longer time for the adsorbent to achieve the adsorption/desorption temperature. This directly reduces the adsorption/desorption rate of the adsorbate on the adsorbent, such as water on zeolite, and results in lower system coefficient of performance (COP) and specific cooling power (SCP). It was proposed that embedding carbon nanotube (CNT) into the 13X/CaCl2 composite absorbents can increase the thermal conductivity of the adsorbent bed to improve the system performance. Thus, the properties of the multi-wall CNT (MWCNT) embedded zeolite 13X/CaCl2 composite adsorbents were investigated to find out the optimized composition for the cooling system. The material properties of the MWCNT embedded zeolite 13X/CaCl2 composite adsorbent were measured. The thermal conductivities of the MWCNT embedded 13X/CaCl2 composite adsorbents were predicted by developing a new theoretical model modified based on area contact model. The performance of the adsorption cooling system using zeolite 13X and MWCNT embedded composite adsorbent were studied numerically. It is found that the COP and SCP are improved by 3.6 and 26 times respectively. This results in a much more compact and energy efficient cooling system.

Heat and Mass Transfer Characteristics of a Zeolite 13X/CaCl2 Composite Adsorbent in Adsorption Cooling Systems

2012 ◽  
Author(s):  
K. C. Chan ◽  
Christopher Y. H. Chao ◽  
M. Bahrami
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
System Performance ◽  
Cooling System ◽  
Design Parameters ◽  
Cooling Power ◽  
Composite Adsorbent ◽  
Zeolite 13X ◽  
Desorption Temperature ◽  
Adsorption Cooling System

The performance of the adsorption cooling system using the zeolite 13X/CaCl2 composite adsorbent was studied using a numerical simulation. The novel zeolite 13X/CaCl2 composite adsorbent with superior adsorption properties was developed in previous studies [11]. It has high equilibrium water uptake of 0.404 g/g between 25°C and 100°C under 870Pa. The system specific cooling power (SCP) and coefficient of performance (COP) were successfully predicted for different operation parameters. The simulated COP with the composite adsorbent is 0.76, which is 81% higher than a system using pure zeolite 13X under desorption temperature of 75°C. The SCP is also increased by 34% to 18.4 W/kg. The actual COP can be up to 0.56 compared to 0.2 for zeolite 13X-water systems, an increase of 180%. It is predicted that an adsorption cooling system using the composite adsorbent could be powered by a low grade thermal energy source, like solar energy or waste heat, using the temperature range of 75°C to 100°C. The performance of the adsorber with different design parameters was also studied in the present numerical simulation. Adsorbents with smaller porosity can have higher thermal conductivity and may result in better system performance. The zeolite bed thickness should be limited to 10mm to reduce the thermal response time of the adsorber. Addition of high thermal conductivity materials, for example carbon nanotube, can also improve the performance of the adsorber. Multi-adsorber tube connected in parallel can be employed to provide large heat transfer surface and maintain a large SCP and COP. The desorption temperature also showed a large effect on the system performance.

scholarly journals Recovery of phosphate from aqueous solution by magnetically recycled modified polishing powder composites

2019 ◽  
Vol 80 (7) ◽  
pp. 1357-1366
Author(s):  
Jianming Liu ◽  
Runying Bai ◽  
Junfeng Hao ◽  
Bowen Song ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Ligand Exchange ◽  
Adsorption Process ◽  
High Adsorption ◽  
Order Model ◽  
Powder Composites ◽  
Langmuir Isotherm Model ◽  
Pseudo Second Order ◽  
Ph Level ◽  
Adsorption Desorption

Abstract This study investigated a magnetically recycled modified polishing powder (CMIO@PP) as an adsorbent of phosphate; the CMIO@PP was synthesized by combining the modified La/Ce-containing waste polishing powder with CaO2-modified Fe3O4 (CMIO). Results indicate that the CMIO@PP nanocomposite presents a crystal structure comprising La (OH)3, Ce (OH)3, and Fe3O4, and that CMIO is uniformly dispersed in the modified polishing powder. The CMIO@PP (1:3) is a suitable choice considering its magnetism and adsorption capacity. The magnetic adsorbent exhibits a high adsorption capacity of 53.72 mg/g, a short equilibrium time of 60 min, and superior selectivity for phosphate. Moreover, the adsorbent strongly depends on the pH during the adsorption process and maintains a large adsorption capacity when the pH level is between 2 and 6. The adsorption of phosphate by the CMIO@PP (1:3) accords with the Langmuir isotherm model, and the adsorption process follows the pseudo-second order model. Meanwhile, adsorption–desorption experiments show that the adsorbent could be recycled a few times and that a high removal efficiency of phosphate from civil wastewater was achieved. Finally, mechanisms show that the adsorption of phosphate by the CMIO@PP (1:3) is mainly caused by electrostatic attraction and ligand exchange.

scholarly journals In-situ synthesis of poly(m-phenylenediamine) on chitin bead for Cr(VI) removal

2020 ◽  
Author(s):  
Jinyu Wei ◽  
Huayu Hu ◽  
Yanjuan Zhang ◽  
Zuqiang Huang ◽  
Xingtang Liang ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
In Situ Polymerization ◽  
High Adsorption ◽  
Adsorption Temperature ◽  
Monolayer Adsorption ◽  
Ft Ir ◽  
High Adsorption Capacity ◽  
User Friendly ◽  
Adsorption Desorption

Abstract In this work, a user-friendly chitin-based adsorbent (CT-PmPD) was synthesized by in-situ polymerization of m-phenylenediamine on chitin bead, which could effectively remove Cr(VI) from water. The structure and morphology of the CT-PmPD were characterized by FT-IR, XRD, SEM, zeta potential and XPS. Specifically, the effect of adsorbed dosage, pH, contact time, adsorption temperature and coexisting salt on the adsorption of Cr(VI) were studied. Besides, the adsorption mechanism of CT-PmPD toward Cr(VI) were also analyzed. Consequenlty, CT-PmPD exhibited a monolayer adsorption and the Langmuir model fitted a Cr(VI) adsorption capacity reaching 185.4 mg/g at 298 K. The high adsorption capacity was attributed to the abundant amino groups of CT-PmPD, which could be protonated to boost the electrostatic attraction of Cr(VI) oxyanions, thus providing electron to reduce Cr(VI). Additionally, the CT-PmPD revealed a good regeneration and reusability capacity, maintaining most of its adsorption capacity even after five cycles of adsorption-desorption. This high adsorption capacity and excellent regeneration performance highlighted the great potential of CT-PmPD for the removal of Cr(VI).

scholarly journals Study of CO2 adsorption and separation using modified porous carbon

2020 ◽  
pp. 174751982093803
Author(s):  
Madhavi Jonnalagadda ◽  
Rumana Anjum ◽  
Harshitha Burri ◽  
Suresh Mutyala
Keyword(s):  
Adsorption Capacity ◽  
Porous Carbon ◽  
Carbon Materials ◽  
Co2 Adsorption ◽  
X Ray Diffraction ◽  
High Adsorption ◽  
X Ray ◽  
Adsorption Of Co ◽  
Adsorption Desorption ◽  
Adsorption Cycle

Porous carbon and La2O3/porous carbon materials are synthesized for the study of CO2 adsorption and separation by the volumetric method. The synthesized adsorbents are characterized by X-ray diffraction, N2 adsorption–desorption isotherms, Raman spectra and scanning electron microscopy with energy-dispersive X-ray analysis. Characterization results confirm the existence of porosity in the synthesized carbon materials and uniform distribution of lanthanum(III) oxide on porous carbon. The CO2 adsorption capacity for porous carbon and La2O3/porous carbon is 21 and 33 cm3 g−1, respectively, at 298 K and 1 bar. High adsorption of CO2 is obtained for La2O3/porous carbon because of the electrostatic interaction between La2O3 and CO2. Moreover, the N2 adsorption capacity is 2.8 cm3 g−1 for porous carbon and 2.2 cm3 g−1 for La2O3/porous carbon at 298 K and 1 bar. The change in N2 adsorption is due to the decrease in surface area. For La2O3/porous carbon, the selectivity of CO2/N2 is 33.5 and the heat of CO2 adsorption is 36.5 kJ mol−1 at low adsorption of CO2. It also shows constant CO2 adsorption capacity in each adsorption cycle.

Development of New Zeolite 13X/CaCl2 Composite Adsorbent for Air-Conditioning Application

2011 ◽  
Author(s):  
K. C. Chan ◽  
Christopher Y. H. Chao ◽  
G. N. Sze-To ◽  
K. S. Hui
Keyword(s):  
Ion Exchange ◽  
Air Conditioning ◽  
Exchange Process ◽  
Total Pore Volume ◽  
Composite Adsorbent ◽  
Zeolite 13X ◽  
Surface Areas ◽  
Ion Exchange Process ◽  
Composite Adsorbents ◽  
Cacl2 Solution

Composite adsorbents synthesized from zeolite 13X and CaCl2 were investigated for applications in solar adsorption systems. The effect of Ca-ion-exchange on the adsorption properties of zeolite 13X was studied. Sodium ions in the zeolite structure were replaced by calcium ions by ion exchange. It was found that the Ca-ion-exchange process decreased the specific surface areas of the Ca-ion-exchanged zeolites while the total pore volumes were increased. The optimized Ca-ion-exchange condition existed when soaking zeolite 13X in 46wt% CaCl2 solution for 36 hours. The increase in the total pore volume is good for further impregnating the zeolite with CaCl2. A large difference in equilibrium water uptake, 0.404g/g, between 25°C and 100°C under 870Pa was recorded for the 13X/CaCl2 composite adsorbent impregnated in 40wt% CaCl2 solution. This was 295% of that of zeolite 13X under the same condition. The 13X/CaCl2 composite adsorbent showed a high potential in replacing vapor compression chillers in producing chilled water for central air-conditioning systems.

scholarly journals Polyethylenimine-Silica Mesoporous Hybrid: A Novel Adsorbent for CO2 Capture

2012 ◽  
Vol 21 (2) ◽  
pp. 096369351202100
Author(s):  
Xin Fu
Keyword(s):  
Adsorption Capacity ◽  
High Porosity ◽  
In Situ Ftir ◽  
High Adsorption ◽  
Surface Areas ◽  
Polycondensation Process ◽  
Cyclic Adsorption ◽  
Adsorption Desorption ◽  
Hydrolysis And Polycondensation

A facile pathway has been developed to synthesize polyethylenimine-modified mesoporous hybrid materials with highly efficient CO2 capturer. It is the special feature of this pathway that there are no surfactants introduced and the amine guest can be dispersed within the channels of the silica materials during the hydrolysis and polycondensation process. The obtained materials exhibit high specific surface areas, high porosity and high CO2 uptake. The amount of polyethylenimine (PEI) has important effect on the surface area, pore size and CO2 adsorption capacity of the adsorbents. For the sample containing 50 wt% PEI, the adsorbent exhibits a high adsorption capacity of 186.6 mg/g-PEI, and in situ FTIR show that CO2 is sorbed on amine sites through the formation of alkylammonium carbamates. The adsorbed CO2 could be desorbed completely from the sample at 150 °C. Moreover, the adsorbents show a stable cyclic adsorption-desorption performance.

scholarly journals Preparation of Carbon-Silicon Doping Composite Adsorbent Material for Removal of VOCs

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2438 ◽  
Author(s):  
Zhenwei Han ◽  
Shunli Kong ◽  
Hong Sui ◽  
Xingang Li ◽  
Zisheng Zhang
Keyword(s):  
Adsorption Capacity ◽  
Fire Retardant ◽  
Freundlich Isotherm ◽  
Maximum Adsorption Capacity ◽  
Silicon Doping ◽  
Composite Adsorbent ◽  
Volatile Organic ◽  
Flame Retardant Properties ◽  
Extrusion Forming ◽  
Adsorption Desorption

The adsorption-desorption combined process has been considered as a promising method for the industrial VOCs (volatile organic compounds) treatment. Herein, a carbon-silicon composite adsorbent material has been prepared for the removal of VOCs at lower potential flammable risk. The preparation involves two main steps: Extrusion forming and thermal treatment. The carboxymethyl cellulose and silicate were adopted as binder and fire retardant respectively. The molding and inflaming retarding mechanisms were proposed and discussed. Results show that the newly prepared doping combined material is micro-mesoporous with a specific surface area of 729 m2/g. The maximum adsorption capacity of carbon-silicon doping combined material to p-xylene is observed to be 292 mg/g. The adsorption is found to be favorable, which is well described by the Yoon-Nelson model and Freundlich isotherm. The combined material is also found to possess reversible adsorption to p-xylene; without sacrificing (<2%) too much adsorption capacity after five adsorption-desorption cycles. The composite materials have an increased ignition temperature of at least 40 °C compared with raw carbon material. These findings suggest that the obtained composite material possesses good adsorption capacity and flame-retardant properties.

Development of Composite Adsorbents of Activated Carbon and Hydrophobic Silica Gel for Gasoline Vapor Adsorption

2011 ◽  
Vol 396-398 ◽  
pp. 512-515 ◽  
Author(s):  
Wei Qiu Huang ◽  
Zhi Lun Hu ◽  
Juan Bai
Keyword(s):  
Activated Carbon ◽  
Adsorption Capacity ◽  
Silica Gel ◽  
Lower Layer ◽  
Optimum Ratio ◽  
High Concentration ◽  
Composite Adsorbent ◽  
Low Concentration ◽  
Hydrophobic Silica ◽  
Composite Adsorbents

A composite adsorbent with upper-layer activated carbon (TY) and lower-layer hydrophobic silica gel (HSG) was developed, based on the comprehensive consideration of both adsorption capacity and adsorption heat of activated carbon and hydrophobic silica. For the composite adsorbent, various volumetric ratio of activated carbon to silica gel was designed, and the adsorption capacity and heat effect of the composite adsorbent with different ratio were investigated. The experimental results showed that the optimum ratio was 1:1. Thus, the vapor with high concentration was early adsorbed by the lower-layer hydrophobic silica gel, and then the residual vapor with low concentration was late adsorbed by the upper-layer activated carbon. In this way, incombustibility of silica gel and high adsorption capacity of activated carbon were fully utilized; accordingly the adsorption operation safety was improved and the adsorption capacity of activated carbon was increased owing to that the activated carbon was only used to adsorb the vapor with low concentration.

CO2 Capture onto Zeolite 13X and Zeolite 4A by Pressure Swing Adsorption in a Fixed Bed

2014 ◽  
Vol 592-594 ◽  
pp. 1456-1460 ◽  
Author(s):  
Lalhmingsanga Hauchhum ◽  
P. Mahanta
Keyword(s):  
Adsorption Capacity ◽  
Pressure Swing Adsorption ◽  
Fossil Fuels ◽  
Gas Adsorption ◽  
Fixed Bed ◽  
Fuel Gas ◽  
Zeolite 13X ◽  
Zeolite 4A ◽  
Pressure Swing ◽  
Adsorption Desorption

Combustion of fossil fuels is one of the major sources of greenhouse gas CO2, it is therefore necessary to develop technologies that will allow us to utilize the fossil fuels while reducing the emissions of greenhouse gases. Pressure swing adsorption (PSA) is a potential technique for removing CO2from high-pressure fuel gas streams. Zeolites are suitable candidate sorbents for use in the PSA process. Studies of the gas adsorption of CO2onto zeolite 13X and zeolite 4A were conducted at a temperature of 25 °C, 35 °C, 45 °C and 60 °C up to a pressure of 1 bar. The data fitting is accomplished with the Toth and Sips adsorption models which are generally used for micro-porous adsorbents such as zeolites. Moreover, regeneration studies have been conducted in order to verify the possibility of adsorbents reutilization, to determine its CO2adsorption capacity within consecutive cycles of adsorption–desorption. Zeolite with higher surface area showed higher CO2adsorption capacity. There is no full reversibility for the two zeolites.

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