This study aimed determination of proper amount of paraffin (
n-docosane) absorbed into expanded graphite (EG) to obtain form-stable composite as phase change material (PCM), examination of the ...influence of EG addition on the thermal conductivity using transient hot-wire method and investigation of latent heat thermal energy storage (LHTES) characteristics of paraffin such as melting time, melting temperature and latent heat capacity using differential scanning calorimetry (DSC) technique. The paraffin/EG composites with the mass fraction of 2%, 4%, 7%, and 10% EG were prepared by absorbing liquid paraffin into the EG. The composite PCM with mass fraction of 10% EG was considered as form-stable allowing no leakage of melted paraffin during the solid–liquid phase change due to capillary and surface tension forces of EG. Thermal conductivity of the pure paraffin and the composite PCMs including 2, 4, 7 and 10
wt% EG were measured as 0.22, 0.40, 0.52, 0.68 and 0.82
W/m
K, respectively. Melting time test showed that the increasing thermal conductivity of paraffin noticeably decreased its melting time. Furthermore, DSC analysis indicated that changes in the melting temperatures of the composite PCMs were not considerable, and their latent heat capacities were approximately equivalent to the values calculated based on the mass ratios of the paraffin in the composites. It was concluded that the composite PCM with the mass fraction of 10% EG was the most promising one for LHTES applications due to its form-stable property, direct usability without a need of extra storage container, high thermal conductivity, good melting temperature and satisfying latent heat storage capacity.
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•A linear polyethyleneimine modified activated carbon (PAF) was prepared as an effective sorbent.•The adsorption capacity of the PAF sorbent for U(VI) was determined to be ...115.31mgg−1.•The recovery yield was determined as 90–95%.
In this study, the polyethyleneimine modified activated carbon/Fe (PAF) was prepared and used as an effective magnetic adsorbent to remove uranium (U(VI)) ions from aqueous solution as a function of batch adsorption parameters. The developed magnetic adsorbent was investigated by FT-IR, SEM, EDX, TG/DSC and BET techniques. The effects of the adsorption parameters on the sorption amount were investigated by using factorial design. In order to study the sorption behavior for U(VI) ions, the Langmuir, and Freundlich isotherm models were applied to fit the equilibrium data. The monolayer adsorption capacity of the magnetic sorbent for U(VI) was determined to be 115.31mgg−1 at pH 5, 20°C and 60min. The kinetic results indicated that the pseudo-second-order kinetic modeling fits the equilibrium data well under employed temperature conditions. The thermodynamic examinations showed exothermic and spontaneous adsorption process. The reusability-cycling test indicated that the magnetic sorbent has good desorption performance. It was also concluded that the PAF magnetic material can be used as an effective adsorbent for the removal of U(VI) ions from wastewaters by taking into account its advantages such as being of cost effective, easy prepare and environmental friendly.
The aim of this study is to prepare a novel form-stable phase change material (PCM) for latent heat thermal energy storage (LHTES) in buildings. A eutectic mixture of capric acid (CA) and myristic ...acid (MA) is incorporated with expanded perlite (EP). Thermal properties, thermal reliability, and thermal conductivity of the form-stable composite PCM are determined. The maximum CA–MA absorption of EP was found to be 55
wt% without melted PCM seepage from the composite, and therefore this mixture was described as a form-stable composite. The form-stable composite PCM was characterized using the FT-IR spectroscopy method. The melting and freezing temperatures and latent heats of form-stable composite PCM were measured using DSC analysis. Thermal cycling test of the form-stable composite PCM indicated good thermal reliability in terms of changes in thermal properties after 5000 thermal cycling. The thermal conductivity of the form-stable CA–MA/EP composite PCM was increased about 58% by adding 10
wt% expanded graphite (EG). The form-stable CA–MA/EP/EG composite PCM was considered as an effective LHTES material in the building energy conservation due to suitable phase change temperatures, high latent capacities, good thermal reliability, and good thermal conductivity.
This paper deals with the preparation, characterization, and determination of thermal energy storage properties of polyethylene glycol (PEG)/diatomite composite as a novel form-stable composite phase ...change material (PCM). The composite PCM was prepared by incorporating PEG in the pores of diatomite. The PEG could be retained by 50
wt% into pores of the diatomite without the leakage of melted PEG from the composite. The composite PCM was characterized by using SEM and FT-IR analysis technique. Thermal properties of the composite PCM were determined by DSC analysis. DSC results showed that the melting temperature and latent heat of the composite PCM are 27.70
°C and 87.09
J/g, respectively. Thermal cycling test was conducted to determine the thermal reliability of the composite PCM and the results showed that the composite PCM had good thermal reliability and chemical stability. TG analysis showed that the impregnated PEG into the diatomite had good thermal stability. Thermal conductivity of the composite PCM was improved by adding expanded graphite in different mass fractions. Thermal energy storage performance of the composite PCM was also tested.
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► Polyethylene glycol (PEG)/diatomite composite as novel form-stable phase change materials. ► Thermal energy storage properties, thermal stability and performance of PEG/diatomite composite. ► The melting point and latent heat of the (PEG)/diatomite are 27.70 °C and 87.09 J/g, respectively. ► The composite PCM can decrease indoor air temperature fluctuation due to heat absorption of the PCM.
The equilibrium, thermodynamics and kinetics of selenium(IV) biosorption from aqueous solution by dead green algae (
Cladophora hutchinsiae) biomass was investigated. Optimum biosorption conditions ...were determined with respect to pH, biomass concentration, contact time, and temperature. The equilibrium data were analyzed using the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. The maximum biosorption capacity of
C. hutchinsiae biomass for Se(IV) was found to be 74.9
mg/g at pH 5, biomass concentration 8
g/L, contact time 60
min, and temperature 20
°C. The biosorption percentage decreased from 96% to 60% as temperature was increased from 20 to 50
°C during the equilibrium time.
From D–R model, the calculated mean biosorption energy (10.9
kJ/mol) indicated that the biosorption of Se(IV) onto
C. hutchinsiae biomass was taken place by chemical ion-exchange.
The highest recovery (95%) was achieved using 0.5
M HCI. The high stability of
C. hutchinsiae permitted a slightly decrease about 20% in recovery of Se(IV) ions after ten times of adsorption-elution process. The calculated thermodynamic parameters, Δ
G° (between −18.39 and −16.08
kJ/mol at 20–50
°C) and Δ
H° (−45.96
kJ/mol) showed that the biosorption of Se(IV) onto
C. hutchinsiae biomass was feasible, spontaneous and exothermic, respectively. The experimental data was also fitted to the Lagergren's first-order and pseudo second-order kinetic models. The results revealed that the pseudo second-order reaction model provided the best description these data with coefficients of determination in range of 0.992–0.999. The biosorption rate constant was calculated as 24.9
×
10
−2
g/(mg
min).
Sepiolite was modified with polymer consisting of ethylenediamine(EDA)-trimesoyl chloride (TMC) to produce a highly effective sorbent for antimony (III) (Sb(III)) adsorption from aquatic solutions. ...The EDA-TMC polymeric branches were grafted onto the surface of sepiolite by polymerization. The surface morphology and the main adsorptive chemical groups of the developed S/EDA-TMC sorbent were characterized by SEM, EDX, BET, and FTIR, analysis methods. The impact of the batch adsorption conditions on the adsorption performance was systematically studied by conducting a factorial design analysis. While Langmuir and Freundlich isotherm models were employed with the non-linear equations to the removal data and the removal capacity of the prepared composite was estimated as 210.1 mg g−1 based on the Langmuir due to relatively high correlation. The kinetic investigation results displayed that the pseudo-second-order kinetic model was well appropriate for characterizing Sb(III) removal mechanism. Also, thermodynamic findings verified that the Sb(III) removal onto the composite adsorbent progressed exothermically and spontaneously with temperature increasing from 24° to 55°C. Besides, the produced adsorbent demonstrated still appreciated adsorption/desorption yield (80/76%) after the 7th cycle. Accordingly, the fabricated S/EDA-TMC material can be evaluated as a powerful sorbent in the cleaning of aqueous solutions containing Sb(III) pollutants.
•Polymer modified magnetic sepiolite adsorbent was synthesized.•Sb(III) adsorption conditions were optimized with factorial design analysis.•Adsorption/recovery performance was considerable high at 7th cycle.
This study deals with preparation, characterization, thermal properties and thermal reliability of
n-eicosane microcapsules as novel phase change material (PCM) for thermal energy storage. The ...microcapsulated PCMs were prepared by coating
n-eicosane with polymethylmethacrylate (PMMA) shell. Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and particle size distribution (PSD) analysis were used to characterize the PMMA/eicosane microcapsules as microcapsulated PCMs. The PSD analysis indicated that the average diameter of microcapsules was found to be 0.70
μm under the stirring speed of 2000
rpm. Thermal properties and thermal reliability of the microcapsules were determined using differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) methods. From DSC analysis, the melting and freezing temperatures and the latent heats of the microcapsules were measured as 35.2
°C and 34.9
°C, 84.2 and −87.5
J/g, respectively. TGA analysis indicated that PMMA/eicosane microcapsules degrade in three steps at considerably high temperatures. Accelerated thermal cycling tests have been also applied to show the thermal reliability of the microcapsules. All results showed that thermal properties make the PMMA/eicosane microcapsules potential PCM for thermal energy storage.
This study is focused on the preparation, characterization and thermal properties of microencapsulated
n-heptadecane with polymethylmethacrylate shell. The PMMA/heptadecane microcapsules were ...synthesized as novel solid–liquid microencapsulated phase change material (microPCMs) by emulsion polymerization method. The chemical and thermal characterization of the microPCMs were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The diameters of microPCMs were found in the narrow range (0.14–0.40
μm) under the stirring speed of 2000
rpm. The spherical surfaces of microPCMs were smooth and compact. The DSC results show that microPCMs have good energy storage capacity. Thermal cycling test showed that the microPCMs have good thermal reliability with respect to the changes in their thermal properties after repeated 5000 thermal cycling. TGA analyses also indicated that the microPCMs degraded in three steps and have good thermal stability. Based on all results, it can be considered that the PMMA/heptadecane microcapsules as novel solid–liquid microPCMs have good energy storage potential.
This work presents the preparation of chitosan-modified vermiculite (C-mVMT) in a facile wet chemistry process. The potential of C-mVMT was investigated for the adsorption of As(III) ions from an ...aqueous solution. The effect of the pH of the solution, adsorbent dosage, contact time, and temperature on the adsorption efficiency was studied systematically. The maximum adsorption capacity of rVMT and C-mVMT sorbents for As(III) was determined as 34.9mg/g and 72.2mg/g, at pH5, with a contact time of 30min and 20°C. The prepared C-mVMT sorbent exhibited good reusability performance, even after ten cycles. The results obtained from the D–R model revealed that the adsorption process were chemically dominant. Thermodynamic parameters (ΔH° and ΔS°) indicated that, under the studied temperature range, the adsorption of As(III) by C-mVMT was feasible and had a spontaneous and exothermic nature. The kinetic model examinations showed that the adsorption processes followed pseudo-second order kinetics well. Based on all the results, the produced C-mVMT can be evaluated as a potentially cost-effective sorbent for As(III) removal from aqueous solutions.
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•Chitosan modified-vermiculite was synthesized by a facile wet chemistry process.•The materials showed high capacity for the adsorption of As(III) ions from aqueous solution.•Thermodynamic parameters indicated that the process spontaneous and exothermic nature.
The aim of this research is the preparation of a novel form-stable composite PCM by incorporation of capric acid (CA) within the expanded perlite (EP), characterization of the composite by SEM and ...FT-IR technique and determination of thermal properties and thermal reliability of the composite PCM using DSC analysis. The maximum proportion of CA as phase change material (PCM) in the composite was found as 55
wt%. This composite was specified as form-stable because it does not allow the melted PCM leakage even when it is heated over the melting point of CA. Thermal properties of the form-stable CA/EP composite PCM were measured using DSC analysis. Thermal reliability of the composite PCM was investigated by thermal cycling test with respect to the changes in its thermal properties. Thermal conductivity of the composite PCM was also increased approximately as 64% by adding 10
wt% expanded graphite.
