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•A broad overview of biochar/LDH-based materials in water purification is presented.•The potential of biochar/LDH for the uptake of pollutants is critically evaluated.•Adsorption ...mechanisms and regeneration capability of biochar/LDH are appraised.•The catalytic degradation of various pollutants by biochar/LDH is reviewed.•Challenges and prospects of biochar/LDH in water treatment are highlighted.
Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.
Hybrids of layered double hydroxide (LDH) are emerging as robust adsorbent materials for the removal of toxic organic dyes from wastewater. The LDH-containing hybrids have shown excellent adsorption ...performance owing to their large surface area and chemical stability. These hybrids are non-toxic, cost-effective, and readily available and can easily be regenerated. Herein, this review aims to summarize the recent progress of LDH-containing hybrids as highly efficient adsorbents for dye removal from aqueous phase. The study discusses various important parameters such as adsorption capacity, surface area, toxicity, and regeneration ability. The effect of adsorption variables such as temperature, adsorbent dosage, pH and contact time has also been briefly reviewed. Moreover, the article also provides insight into adsorption mechanisms and adsorption kinetics.
•A review of LDH for dyes removal is presented.•Synthesis routes for LDH are discussed.•Adsorption performance of LDH-based hybrids is rated excellent.•Factors affecting the adsorption performance of LDH are discussed.•Thermal and chemical methods can be used to regenerate the LDH adsorbents.
This paper reports the study of in‐situ incorporation of NiFe‐(Anion) layered double hydroxides (LDH) in the ethylene‐propylene (EP) (95:05 molar ratio) copolymerization. NiFe LDHs were synthesized ...with different intercalated anions using the coprecipitation method. The EP/LDH nanocomposites showed improved thermal stability, nevertheless, the various types of intercalated anions in the LDH showed a remarkable effect on the thermal stability and the degradation mechanism of the resultant polymer nanocomposites. EP/LDH constituted with NiFe‐CO3/A (A = acetone washed) showed maximum improvement in the thermal stability concerning neat EP. The LDH incorporation in the composite influenced the polymer microstructure which was evident from the DSC and CRYSTAF analysis. The degradation kinetics of neat EP and EP/LDH nanocomposites were studied by employing the isoconversional method. The degradation kinetics models of different polymer samples were predicted by applying a generalized master plot. Moreover, EP nanocomposites exhibited higher storage modulus and elasticity as compared to neat EP copolymer.
This study investigated the impact of pyrolysis conditions on physical characteristics of date palm fronds biochars and their performances for aqueous uptake of anionic dyes—methyl orange (MO) and ...Eriochrome Black-T (EBT)—and cationic dyes—methylene blue (MB) and crystal violet (CV). Detailed characterization of the biochars revealed the formation of oxygen functionalities (C=O, C-O-C, and C-O), improved surface characteristics (surface area and pore volume) and high ash content at higher pyrolysis temperature and time. Biochar-derived date palm with a high surface area of 431.82 m
2
/g and a pore volume of 0.134 cm
3
/g was obtained at pyrolysis temperature and time 700 °C and 4 h, respectively. For all the four investigated dyes, the adsorption isotherm was mainly described by Redlich–Peterson isotherm model (
R
2
> 0.95), while the adsorption kinetics well-fitted the pseudo-second order model. The biochar yielded fast dyes adsorption with maximum adsorption capacity for MB, EBT, MO, and CV dye of up to 206.61, 309.59, 163.132, and 934.57 mg/g at 200 mg/L dye concentration, respectively. The adsorption of cationic dyes was pH-independent indicating the involvement of pi–pi and chemical interactions. However, the uptake of the anionic dye was favorable at acidic conditions and was dominated by electrostatic interactions involving ion exchange and chemical reactions. The produced biochars exhibited excellent surface characteristics and enhanced adsorptive performance relative to other similar adsorbents. Thus, the direct pyrolysis of date palm fronds’ waste is a sustainable and economical approach of converting a huge quantity of wastes into excellent adsorbent for effective remediation of dye-contaminated water and wastewater.
In this study, the effect of polymer structure, the degree of hydrolysis, chemical structure of monomer in the backbone, and charge distribution of monomer groups on rheological and filtration ...properties of Bentonite (Bent)/polymer dispersions were assessed. Two different water-soluble polymers were employed to investigate the rheological and filtration properties of Bent/polymer dispersions. The polymers evaluated are a copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (AM-AMPS) (P1) and a terpolymer of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and N-Vinylpyrrolidone (AM-AMPS-NVP) (P2). The objective of this work was to study the rheological and filtration properties of Bent/polymer dispersions in deionized and salt water at different temperatures (25°C and 85°C). The steady shear rheological data was fitted to Herschel-Bulkley model to compute rheological parameters like yield stress, consistency index, and flow behavior index. The incorporation of polymers in Bent dispersions improved the rheological properties of the Bent dispersions. Addition of electrolyte in Bent/polymer dispersions led to a slight decrease in the rheological properties of all developed dispersions. The Bent/P2 dispersion revealed superior rheological properties compared to the other Bent and Bent/polymer dispersions in both deionized and salt water. TEM analysis of Bent/polymer dispersions was carried out to study the morphology of dispersions. LP/LT and HP/HT filtration experiments were performed in deionized and salt water at 25°C and 85°C, respectively, and results showed that Bent/P2 dispersion had minimum filtrate volume and filter cake thickness compared to the Bent dispersion. The permeability of filter cakes was determined using Darcy's law and filter cake morphologies were studied using SEM analysis. The excellent rheological and filtration properties of Bent/P2 dispersion was attributed to the presence of NVP monomer group in P2 polymer, which is stable towards elevated temperatures and high salinity environments. The exceptional filtration and rheological properties of P2 polymer make it a suitable candidate for the development of high-performance drilling fluids.
•Impact of polymer structure on rheological and filtration properties of bentonite/polymer dispersions•Effect of temperature and electrolyte on rheological and filtration properties•N-Vinylpyrrolidone monomer enhances the rheological and filtration properties of bentonite/polymer dispersions
In this work, the impact of molecular structure such as the degree of hydrolysis (DOH) and nature of comonomers in acrylamide-based copolymers on the rheological and filtration properties of ...bentonite dispersions was assessed using three different water-soluble polymers for water-based drilling fluids. These polymers are (1) copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) with 10% DOH (P1), (2) copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (P2) with 25% DOH, and (3) copolymer of acrylamide and acrylic acid (P3) with 15% DOH. Steady shear rheology data was fitted to the Herschel-Bulkley model and flowability test was performed at 25°C and 85°C. Aging of bentonite and bentonite/polymer dispersions was performed at 90°C for 16h. Results showed that the incorporation of polymers in bentonite enhanced the filtration and rheological properties. The bentonite/P3 dispersion showed better rheological properties compared to other bentonite/polymer dispersions. The better rheological properties of bentonite/P3 dispersion suggest that acrylamide-based copolymers containing smaller comonomers such as acrylic acid are better compared to the bulky comonomers such as AMPS for drilling fluids applications. The filtration properties are less affected by the DOH and nature of comonomers, nevertheless, all polymer/bentonite dispersions showed better filtration properties compared to bentonite dispersion. The use of this high molecular weight polymer provides high thermal stability, superior rheological properties and better filtration characteristics for water-based drilling fluids.
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•Novel drilling fluids containing high molecular weight polymers•Impact of polymer structure on filtration properties of drilling fluids•High molecular weight polymers enhanced the filtration properties of bentonite.•Acrylamide copolymers with smaller comonomers are better for drilling fluids.
The nanocomposites of poly(vinylidene fluoride) (PVDF) with pristine graphene nanoflakes (GNF) and a multi-wall carbon nanotube (MWCNT) were prepared by the solution casting method. Additionally, the ...GNF and MWCNT were functionalized by acid treatment, and nanocomposites of the acid-treated MWCNT/GNF and PVDF were prepared in the same method. The effect of the acid treatment of MWCNT and GNF on the mechanical, thermal and thermo-oxidative stability and the thermal conductivity of the MWCNT/GNF-PVDF nanocomposites was evaluated, and the results were compared with the untreated MWCNT/GNF-PVDF nanocomposites. In both cases, the amount of GNF and MWCNT was varied to observe and compare their thermal and mechanical properties. The functionalization of the GNF or MWCNT resulted in the change in the crystallization and melting behavior of the nanocomposites, as confirmed by the differential scanning calorimetry analysis. The addition of the functionalized GNF/MWCNT led to the improved thermal stability of the PVDF nanocomposites compared to that of the non-functionalized GNF/MWCNT-PVDF nanocomposites. The thermal and electrical conductivity of the functionalized and non-functionalized GNF/MWCNT-PVDF composites were also measured and compared. The functional groups, crystal structure, microstructure and morphology of the nanocomposites were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.
The synthesis of polar functionalized polyolefin (PFP) offers improvement in mixing properties, polymer surface, and rheological properties with the potential of upgraded polyolefins for modern and ...ingenious applications. The synthesis of PFP from metal‐based catalyzed olefin (non‐polar in nature) copolymerization with polar comonomers embodies energy‐efficient, atom‐efficient, and apparently an upfront methodology. Despite their outstanding success during conventional polymerization of olefin, 3rd and 4th group (early transition metal)‐based catalysts, owing to their electrophilic nature, face challenges mainly due to Lewis basic sites of the polar monomers. On the contrary, late transition metal‐based catalysts have also made progress, in recent years, for PFP synthesis. The recent past has also witnessed several advancements in the development of dominating palladium‐based catalysts while their lower resistance towards ligand functional groups has limited the practical application of abundant and cheaper nickel‐based catalysts. However, the relentless efforts of the scientific community, during the past half‐decade, have indicated rigorous progress in the development of nickel‐based catalysts for PFP synthesis. In this review, we have abridged the recent research trends in both early as well as late transition metal‐based catalyst development. Furthermore, we have highlighted the role of transition metal‐based catalysts in influencing the polymer properties.
The synthesis of polar functionalized polyolefin, in particular, polyethylene offers unique and superior characteristics of these functionalized materials. The transition metal‐based ethylene copolymerization with a wider range of polar comonomers has emerged in recent years and advancement in the field has seen a rapid increase quite recently. These advancements have provided an opportunity to the scientists to explore ways for commercialization of functionalized polyolefins.
Date palm ash (DPA) and MgAl-layered double hydroxide (LDH) composites were synthesized by the co-precipitation method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning ...electron microscope (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET). The DPA-MgAl-LDH (DPA/MgAl) composites were employed for the removal of methyl orange (MO) and eriochrome black-T (EBT) from aqueous phase. Incorporation of 33.33% (
w
/
w
) DPA into the layers of MgAl increased the surface area from 44.46 to 140.65 m
2
/g, which leads to the improved adsorption performance. The maximum adsorption capacity of DPA/MgAl (1:2) at 298 K was 242.98 and 425.16 (mg/g) for MO and EBT, respectively. The adsorption data of dyes were adequately fitted by a pseudo-second-order and Langmuir isotherm model. The composite showed excellent reusability performance up to three cycles. Addition of DPA into MgAl-LDH resulted in an effective low-cost adsorbent for decontamination of dyes from wastewater.
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Electrical and dielectric properties of poly(vinyl alcohol) (PVA) films, and PVA/starch blend and its nanocomposites with graphene were investigated. The tested materials were prepared via solution ...mixing and an evaporative casting technique using glycerol as a plasticizer. Differential scanning calorimetric (DSC) measurement data was used to calculate the percentage of crystallinity and glass transition temperature (Tg). Distribution of starch and graphene in the PVA matrix was determined from field emission scanning electron microscopy (FESEM). Effects of the plasticizer and graphene loading on the DC and AC electrical conductivities of the PVA/starch blend were studied. The impact of graphene loadings on the dielectric permittivity (ϵ′), dielectric loss tangent (tan δ), complex electric modulus (M*), and complex impedance (Z*) as a function of frequency were reported. The DC conductivity of PVA was increased with the addition of glycerol and starch. The permittivity of PVA films and PVA/starch/graphene nanocomposites showed a strong frequency‐dependent behaviour in a low frequency zone. The addition of graphene to the PVA/starch blend reduced the area under the semicircles of the Nyquist plot.
