This work reports the preparation of zeolite hydrogel composite (ZHC) based on κ-carrageenan (KC) and AQSOA-Z05 zeolite and its potential use in water remediation applications for methylene blue (MB) ...dye adsorption. The ZHC was synthesized via the graft-copolymerization technique using the crosslinked hydrogel of KC as polymer matrix. Effects of incorporating zeolite particles within the hydrogel matrix on the properties were studied using different characterization techniques such as TEM, X-ray diffraction, SEM and FTIR. The hydrogel composite with 8% loading of zeolite exhibited maximum swelling capacity (3.481%) among the synthesized ZHCs. For MB removal, ZHC adsorbed 99% dye with 0.4 g L
−1
adsorbent dose in the neutral pH solution. Furthermore, the adsorption of MB onto ZHC followed pseudo-second-order and Langmuir isotherm models. The ZHC exhibited maximum adsorption capacities of 661.91 at 298.18 K, 674.05 at 308.15 K and 682.67 mg
dye
g
ads
−1
at 318.15 K. Dye diffusion mechanism partially followed both liquid film and intra-particle diffusion mechanisms. Results obtained from thermodynamics experiments suggested the endothermic nature of the MB adsorption on ZHC. MB was selectively adsorbed from the binary dye mixtures having MB and methyl orange in different concentration ratio. In addition, the ZHC showed excellent adsorption behavior for six continuous adsorption–desorption cycles. Therefore, the synthesized ZHC has all the properties to be used as a potential adsorbent for the treatment of cationic dyes contaminated wastewater.
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•GK-cl-P(AA-cl-AAM)/SiO2 nanocomposite (HNC) was synthesized using grafting method.•Cross-linked hydrogel nanocomposite was used for the removal of methylene blue.•A superior maximum ...adsorption capacity was found to be 1408.67mgg−1.•Adsorption process was spontaneous and endothermic in nature.•The HNC was used successfully for three cycles of adsorption–desorption.
The aim of this work was to study the adsorption behavior of the nanosilica-containing hydrogel nanocomposite of gum karaya grafted with poly(acrylic acid−acrylamide) (GK-cl-P(AA-co-AAM)) in the adsorption of methylene blue (MB) from aqueous solutions. The hydrogel nanocomposite was synthesized by the base-catalyzed hydrolysis and water condensation reactions of tetraethylorthosilicate in an aqueous medium containing a dispersion of GK-cl-P(AA-co-AAM). Structural and morphological characterizations using Fourier transform infrared spectroscopy, X-ray diffraction, and transmission and scanning electron microscopies supported the formation of the grafted hydrogel polymer of GK and the SiO2-containing nanocomposite. The Brunauer–Emmett–Teller adsorption studies showed that the surface area and porosity of the hydrogel polymer significantly increased after nanocomposite formation with SiO2. The hydrogel nanocomposite was employed for the removal of MB from an aqueous solution: 96% of the MB was removed with a hydrogel nanocomposite dose of 0.2gL−1. The adsorption process was found to follow pseudo-second-order kinetics, and the adsorption isotherm was best fitted with the Langmuir monolayer isotherm model with a maximum adsorption capacity of 1408.67mgg−1, which was much higher than that of the hydrogel polymer. Different adsorption thermodynamic parameters supported the endothermic nature as well as the spontaneity of the adsorption process. The hydrogel nanocomposite showed excellent regeneration capacity in the acidic medium and was successfully used over three adsorption–desorption cycles. Therefore, the GK-cl-P(AA-co-AAM)/SiO2 hydrogel nanocomposite has shown potential as an efficient adsorbent for the highly effective removal of cationic dyes from aqueous solution.
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This study investigates the potential application of superporous hydrogels (SPHs) and their composites with Laponite-RD (Lap-RD) for the adsorption of water vapors from humid air. ...Super-hydrogel composites (SPHCs) wee synthesized via gas blowing and foaming technique. Synthesized adsorbents were characterized using different techniques such as fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermos-gravimetric analysis (TGA). The incorporation of Lap-RD within the polymer matrix increased its thermal stability. Further, P(AA-co-AM) SPHs as well as SPHCs were used to adsorb water vapors from humid air. The adsorption of water vapors in both of these materials exhibited type-III isotherm with a maximum adsorption capacity of 1.03 and 1.24 gw/gads for P(AA-co-AM) SPH and SPHC at 25 °C, respectively. Higher adsorption capacity of SPHC was due to the combined effects of capillary condensation and the presence of hydrophilic Lap-RD particles within the polymer matrix. Adsorption isotherm for both materials followed Guggenheim, Anderson and Boer (GAB) model which suggested that the main driving force for water vapors adsorption was capillary condensation. The adsorption capacity of both materials decreased with increasing temperature. Furthermore, the adsorption capacity for these materials was quite low in the relative humidity range of 20–50 % which increased abruptly with increasing the relative humidity above 50 %. The isosteric heat of water vapors adsorption for P(AA-co-AM) SPHs and SPHC were found to be in the range of 59−48 and 57−49 kJ/mol, respectively. Adsorption kinetics followed linear driving force model and the diffusion of water molecules followed non-Fickian type diffusion mechanism. Finally, the synthesized adsorbents showed very good reusable efficiency and used successfully for ten cycles of adsorption.
Dehumidification performance of most polymer desiccant materials is unsatisfactory because of the complex adsorption mechanism on polymer surface and non-porous structure. A viable alternative of ...solid desiccants, especially existing polymer desiccants, for capturing water vapors from moist air is the super-porous gels (SPGs). The presence of interconnected channels of pores in its structure facilitates the transfer of water molecules to the internal structure of SPGs. Therefore, in this research work, we are proposing N-isopropylacrylamide (NIPAM) and acrylamide (AM) based thermoresponsive SPGs as a potential alternative to the existing conventional solid desiccants. To ensure the formation of interconnected capillary channels, the SPGs were synthesized via gas blowing and foaming technique. Surface morphology of the SPGs was studied using scanning electron microscopy (SEM) and the other physio-chemical characteristics were studied using different techniques like fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Water vapors adsorption properties of the SPGs were explored via adsorption isotherm and kinetics. The adsorption isotherm was found to be of type-III isotherm with a maximum adsorption capacity of 0.75 g
/g
at 25 °C and 90% relative humidity. Experimental isotherm data correlated well with BET, FHH and GAB isotherm models. Adsorption kinetics suggested that the water vapors diffusion followed intraparticle diffusion and liquid field driving mechanisms collectively. SPGs exhibited very good regeneration and reusability for ten continuous adsorption/desorption cycles. Therefore, the dehumidification efficiency of synthesized SPGs shows that they have potential to replace most of the conventional solid desiccant materials in use.
•Magnetic carbonaceous adsorbent (MCA) was hydrothermally prepared from corn starch.•MCA was used for the removal of methylene violet (MV) from wastewater.•MV adsorption onto MCA followed the ...Langmuir isotherm model.•The above adsorption was spontaneous and endothermic.•MCA could be successfully re-used in six adsorption-desorption cycles.
Herein, we report the low-temperature hydrothermal synthesis of a novel magnetic carbonaceous adsorbent (MCA) from corn starch for the adsorptive removal of methylene violet (MV) from aqueous solutions. Specifically, the carbon precursor hydrothermally synthesized at 453 K was magnetized at the same temperature, and MCA formation was confirmed by structural and morphological analyses based on Fourier transform infrared spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The as-prepared MCA was employed for the adsorptive removal of MV from aqueous solutions, with the adsorption process found to follow the Langmuir isotherm model (99% dye removal), exhibiting pseudo-first-order and pseudo-second-order kinetics and featuring contributions from both intraparticle and liquid film diffusion processes. In addition, thermodynamic characterization revealed the endothermic nature and spontaneity of the above adsorption. Importantly, MCA showed an excellent regeneration capacity in acetone and could be successfully re-used in six consecutive adsorption–desorption cycles, thus being an efficient sustainable adsorbent for highly effective cationic dye removal from wastewater.
The current study focused on the use of gum Arabic grafted polyacrylamide (GA-cl-PAM) hydrogel as a self-template for the in situ synthesize of zinc oxide nanoparticles (ZnO NPs) and the application ...of synthesized nanocomposite as a potential adsorbent to remove synthetic dyes especially malachite green (MG) from aqueous solution. Different characterization techniques supported in situ synthesis of ZnO NPs onto polymer matrix. The gum Arabic-crosslinked-poly(acrylamide)/zinc oxide nanocomposites (i.e., GA-cl-PAM/ZnO nanocomposite) exhibited much better surface properties as compared to the parental hydrogel matrix. The swelling abilities of the GA-cl-PAM/ZnO nanocomposites with different concentrations of acrylamide were also checked and the nanocomposite with 7.03 × 10
–4
mol/L of acrylamide exhibited maximum swelling capacity of 2354%. The nanocomposite adsorbed approximately 99% MG dye with 0.4 g/L adsorbent dose at neutral pH. Adsorption kinetics and isotherm followed pseudo-second-order and Langmuir isotherm models, respectively with the high adsorption capacity of 766.52 mg
d
/g
ads
at 25 °C. It was observed that the dye molecules were adsorbed onto GA-cl-PAM/ZnO nanocomposite mostly via electrostatic interactions, hydrogen-bonding and pore-diffusion mechanisms. Diffusion of dye molecules within the internal structure of GA-cl-PAM/ZnO nanocomposite followed the combination of both liquid film as well as intraparticle diffusion mechanisms. Furthermore, nanocomposite was applied ten times consecutively to adsorb MG dye from aqueous solution. Therefore, GA-cl-PAM hydrogel have capability to be used for the in situ ZnO NPs synthesis and thus synthesized nanocomposite can be used effectively to treat dyes polluted wastewater.
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•The values of pzc confirmed the behaviour of the successfully synthesized adsorbents at low and high pH.•The isotherm models predicted the adsorption of cadmium on the outer and ...inner layer of the adsorbents.•The hybrid hydrogel composite exhibited higher affinity for Cd compared to GL–cl–PAAm.•Cd uptake by both adsorbents was found to be an endothermic and spontaneous process.•The two adsorbents showed good potential for the removal of metals from AMD.
This research paper reports on the utilization of the hydrogel of gelatine (GL) and its hybrid nanocomposite with clinoptilolite for the adsorption of Cd2+ ions from an aqueous solution and multi-metal ions from mine effluents. The hydrogel was synthesized using the graft co-polymerization of acrylamide (AAm) onto GL and the hybrid hydrogel nanocomposite was prepared by incorporating clinoptilolite within the hydrogel matrix. The synthesized polymers were characterized using different characterization techniques such as FTIR, XRD, SEM and TGA. The adsorption behaviour of the synthesized adsorbents for the adsorption of Cd2+ was studied using different adsorption parameters such as pH, temperature and adsorbent dosage. Adsorption kinetics followed the pseudo-second-order rate equation, whereas, the adsorption isotherm followed both the Freundlich and Langmuir isotherm models. The thermodynamics studies revealed that the adsorption processes were spontaneous and endothermic in nature. Moreover, the synthesized adsorbents were also successfully utilized for the adsorption of different metal ions from the mine effluents.
Urbanization is leading towards the change of local wind climate in the vicinity of tall buildings, which influences the pedestrian level wind environment to an uncomfortable or even dangerous level. ...Therefore nowadays, building design should not be limited only for the consideration of wind load and indoor environment, but outdoor wind environment should also be considered. This study presents a review of the methods for the assessment of pedestrian level wind climate, different wind comfort criterion and various techniques to evaluate the wind speed at the pedestrian level. In later sections, brief review for the influence of different parameters related to building design and configuration on pedestrian level wind is presented. After analyzing previous literature it is suggested that there is a strong need for the homogenization of different wind comfort criterion, as it may lead to different consequences for the architects. Among various wind tunnel measurement techniques, use of Irwin probe is simple and accurate compared to hot-wire anemometry and it can be installed at numerous locations for simultaneous measurement of pedestrian level wind speed. For numerical simulation, Reynolds Averaged Navier Stokes based technique has been used by various researchers, although this technique is not accurate as much as large eddy simulation and detached eddy simulation. But this technique is cost effective and requires less computing resources.
•Wind comfort due to high as well as low wind speeds should be considered.•Irwin probes provide relatively accurate measurements of wind speed.•Reynolds Averaged Navier Stokes based method is economic to simulate urban wind flow.•Corner modified and lift-up buildings and use of podiums are positive design approach.•Building width at 1/3rd height from ground affects the pedestrian wind mostly.
Deliquescent salts are well known for their high-water vapor adsorption capacity, but they form crystalline hydrates and dissolve in adsorbed water; therefore, they cannot be used in most water vapor ...adsorption applications. To counter this issue, we fabricated solid polymer desiccants comprising polyacrylic acid (PAA) and sodium chloride (NaCl), which were able to capture water vapors from humidity in large quantities and avoid the dissolution of NaCl by keeping it intact inside the polymer matrix. Polymer desiccants, i.e., super-porous hydrogels (SPHs), were synthesized using gas-blowing and foaming techniques to create a porous structure. Due to dense capillary channels, the polymer matrix alone (i.e., without NaCl salt) could capture a high amount of water vapors (0.82 g
w
/g
ads
). Introducing NaCl salt in the polymer matrix drastically improved desiccant performance (3.1 g
w
/g
ads
). Further, the polymer matrix avoided salt dissolution in the adsorbed water and kept it intact within the polymer matrix. Adsorption isotherm was found to be type-III isotherm and best explained using GAB and FHH isotherm models, suggesting that the high desiccant performance of synthesized solid polymeric adsorbents was due to the presence of dense capillary channels in the polymer structure and the presence of NaCl salt within the polymer matrix. The adsorption kinetics followed the linear driving force (LDF) model and the case-II type diffusion mechanism. The desorption performance and kinetics of water release from fully hydrated desiccant samples after capturing water vapors were studied at different temperatures, suggesting that the water release rate depends highly on desorption temperature. Furthermore, the synthesized desiccants exhibited good cyclic performance for six adsorption cycles with a little loss in the desiccant performance.
Pedestrian level wind comfort, natural ventilation and pollutant dispersion are strongly influenced by building shape and orientation. In the recent years, the trend of building shape is not ...restricted to basic square and rectangular cross-section, and various unconventional shapes are also considered. Considering this fact, the present study is focused on the investigation of different building shape with major and minor modifications on the pedestrian level wind environment and aims to evaluate the effect of different building shapes on the extent of different wind conditions surrounding the building systematically. An investigation was performed using a computational fluid dynamics (CFD) approach based on realizable
k
-
ε
model and the standard
k
-
ε
turbulence model with revised closure coefficients for different orientation (
θ
=
0
∘
,
22
.
5
∘
and
45
∘
) and shape of buildings. Further, wind tunnel experiment was conducted to validate the CFD results. The results of CFD simulations obtained using realizable
k
-
ε
model fairly match with experimental values for high wind speed conditions, whereas the standard
k
-
ε
with LK modification and revised closure coefficients performs better for the low wind speed regions. It was observed that the wind conditions at the pedestrian level are influenced mostly by corner modification and projected width at 1/3rd height of the building from the ground.
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