Siloxane Groups Research Articles

Stability investigation of polyPOSS-imide membranes for H2 purification and their application in the steel industry

In the present work, the high-temperature and long-term hydrothermal stability of novel polyPOSS-imide membranes for high-temperature hydrogen separation is investigated. The polyPOSS-imide membranes are found to exhibit an appropriate stability up to 300 °C. Above this temperature the membrane selectivity rapidly decreases, which is seemingly related to changes in the molecular structure coupled to silanol condensation forming siloxane groups. Surprisingly, the exposure of the membrane to temperatures of up to 300 °C even increases the H 2 permeance together with the selective feature of the polyPOSS-imide layer. Subsequently, the long-term hydrothermal stability of the polyPOSS-imide membranes was investigated over a period of close to 1000 h at 250 °C exposing the membrane to 10 mol% steam in the feed. An increase in H 2 /CH 4 selectivity was observed upon water addition, and even though a minor drop was noticed over time during the hydrothermal operation, the selectivity exceeds the initial selectivity obtained in the dry feed atmosphere. After the removal of steam from the feed the performance returns to its original state prior to the exposure to any steam showing an appropriate steam stability of the polyPOSS-imide membranes. A conceptual process design and assessment was performed for application of these membranes involving a combination of carbon reuse and electrification of the steel making process with co-production of hydrogen. The results indicate a CO 2 avoidance of 14%. The CO 2 reduction achieved using renewable electricity in the proposed scheme is a factor 2.76 higher compared to a situation where the same renewable electricity would be fed in the electricity grid. • Exposure of the polyPOSS-imide membrane to 300 °C increases the H 2 permeance. • Long-term hydrothermal stability of polyPOSS-imide membranes proven. • Membranes were operated over a period of 1000 h. • Process evaluation for implementation in the steel industry performed.

Mechanism of organosilicate polymer as high-temperature resistant inhibitor in water-based drilling fluids

To meet the technical requirements of high-temperature drilling engineering, a highly inhibitive, high-temperature-resistant shale inhibitor for water-based drilling fluids (WBDFs) is crucial. This paper reports a new type of small molecule organosilicate polymer (ADMOS) was synthesized through emulsion polymerization. Its inhibitive properties were evaluated using the linear swell test and cutting dispersion test, The results were compared to those for other conventional inhibitors. The results show that ADMOS forms a hydrophobic polymer membrane through chemical and physical synergistic adsorption, which effectively increases the inhibition of clay hydration expansion and dispersion. Its performance is better than that of other common inhibitors. The chemical adsorption of Si-O-Si bonds between ADMOS and clay particles was confirmed for the first time through the 29Si NMR experiment. Further, the introduction of siloxane groups in the ADMOS molecular chain effectively strengthens the adsorption stability of polymer inhibitors in high-temperature environments (150 °C) and has potential application in high-temperature deep wells.

Plasma Co-Polymerization of HMDSO and Limonene with an Atmospheric Pressure Plasma Jet

Plasma co-polymers (co-p) were deposited with an atmospheric pressure plasma jet (APPJ) using a precursor mixture containing hexamethyldisiloxane (HMDSO) and limonene. A coating with fragments from both precursors and with siloxane, carbonyl and nitrogen functional groups was deposited. The flow rate of limonene was found to be an important parameter for plasma co-polymerization to tune the formation and structure of the functional groups. The FTIR and XPS analysis indicates that with increasing flow rate of limonene a higher proportion of carbon is bound to silicon. This is related to a stronger incorporation of fragments from limonene into the siloxane network and a weaker fragmentation of HMDSO. The formation mechanism of the nitroxide and carboxyl groups can be mainly differentiated into in-plasma and post-plasma reactions, respectively.

Potential Applications of Halloysite Nanotubes as Drug Carriers: A Review

Halloysite nanotubes (HNTs) are naturally occurring tubular clay nanomaterials that are made from multiple‐rolled aluminosilicate kaolin panels. The aluminol and siloxane groups on the surface of HNT facilitate the formation of hydrogen bonds with biomaterials on its surface. It is a cost‐effective nanomaterial that found applications in a variety of fields of science and technology. The biocompatible properties of HNT resulted in various applications such as in nanomedicine, biomedicine, tissue engineering, drug delivery, sequence delivery, cancer, stem cells isolation, bioimaging, and sensors. Due to its tubular form, it has played a vital role as drug delivery carriers, superior nanocarrier for numerous medicines, and biological agents with larger loading capacity and longer releasing kinetics. HNT has also been investigated and used extensively in targeted drug transfer applications with a variety of medicines. These studies provided positive outcomes which have led to versatile medicinal applications. Herein, we have highlighted the latest developments on HNT‐based drug carriers.

Influence of Nanosilica on Solvent Deasphalting for Upgrading Iraqi Heavy Crude Oil

In this study, the upgrading of Iraqi heavy crude oil was achieved utilizing the solvent deasphalting approach (SDA) and enhanced solvent deasphalting (e-SDA) by adding Nanosilica (NS). The NS was synthesized from local sand. The XRD result, referred to as the amorphous phase, has a wide peak at 2Θ= (22 - 23º) The inclusion of hydrogen-bonded silanol groups (Si–O–H) and siloxane groups (Si–O–Si) in the FTIR spectra. The SDA process was handled using n-pentane solvent at various solvent to oil ratios (SOR) (4-16/1ml/g), room and reflux temperature, and 0.5 h mixing time. In the e-SDA process, various fractions of the NS (1–7 wt.%) have been utilized with 61 nm particle size and 560.86 m²/g surface area in the presence of 12 ml/g SOR with 0.5 hr. mixing time at room and reflux temperature. The results showed that heavy crude was upgraded maximally using 7 wt.% of NS. The API increased to 35.9, while the asphaltene reduction increased to 87.22%. The removal of sulfur, vanadium, and nickel increased to 51.17%, 55.07%, and 69.87%, respectively.

Synthesis and Characterization Nanosilica from Rice Husk Ash Using Sol-Gel Method with Addition Of PEG-6000 and PVA

<p>Nano-silica (NS) from rice husk ash was successfully synthesized using a sol-gel process with the addition of <em>po</em><em>lyethylene</em> glycol (PEG) 6000 and polyvinyl alcohol (PVA) as a template. The purpose of this study is to investigate the properties of NS functional groups and the effect of PEG6000 and PVA concentrations (5%, 10%, and 15% (b / v)) on the size, morphology, and distribution of nanosilica. The functional groups of NS are characterized by Fourier transform infrared (FTIR), the size and morphology of NS are characterized by scanning electron microscopy (SEM). In contrast the size analyzer characterizes the particle size distributionof particulate matter (PSA). The results indicated that the addition of PEG-6000 and PVA affected the size and morphology of NS. The FTIR spectra showed the presence of silanol (Si-OH) and siloxane (Si-O-Si) groups. According to the SEM results, the morphology of NS -PEG is round and relatively more uniform than the amorphous morphology of NS-Control and NS-PVA. Instead of PEG-6000, Sol-gel PVA can be obtained with a narrow particle size distribution.</p>

Fabrication of UV/moisture dual curing coatings based on fluorinated polyoxetanes for anti-fouling applications

In this paper, a novel UV/moisture dual curing hybrid coating was designed. The hybrid coating is composed of two fluorinated polyoxetane resins: Pentaerythritol triacrylate (PETA) end-capped poly(3-trifluoroethoxymethyl-3-ethyloxetane) (P3F), which designed as U-P3F-1 and can be cured by UV irradiation and isocyanatopropyltrimethoxysilane (IPTS) end-capped P3F, which designed as S-P3F-2 and can be cured by moisture in ambiance. The structure of U-P3F-1 and S-P3F-2 was characterized by Fourier infrared transform spectroscopy (FI-IR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). The optimal mixing ratio of the two resins in the hybrid coating was discussed. Moreover, the UV and moisture curing process, thermal properties and surface properties of the hybrid coatings were also studied. Results show that the dual-cured hybrid coating process a high conversion of double bonds and siloxane groups in the presence of UV irradiation and moisture. Besides, the surface energy of the hybrid coating is as low as 18.2 mN/m, showing excellent hydrophobicity and antifouling properties. The XPS results further reveal that the migration and orientation of the fluorine groups to the surface is a significant factor in the low surface energy. In addition, the hybrid coating also demonstrates excellent transparency, durability, and solvent resistance. This study shows that this hybrid coating, with its adjustable resin composition and energy-efficient curing procedure, represents a novel strategy for preparing antifouling coatings and has significant industrial application potential.

Synthesis of Biobased and Hybrid Polyurethane Xerogels from Bacterial Polyester for Potential Biomedical Applications.

Organic–inorganic xerogel networks were synthesized from bacterial poly (3-hydroxybutyrate) (PHB) for potential biomedical applications. Since silane-based networks usually demonstrate increased biocompatibility and mechanical properties, siloxane groups have been added onto polyurethane (PU) architectures. In this work, a diol oligomer (oligoPHB-diol) was first prepared from bacterial poly(3-hydroxybutyrate) (PHB) with an environmentally friendly method. Then, hexamethylene diisocyanate or biobased dimeryl diisocyanate was used as diisocyanate to react with the short oligoPHB-diol for the synthesis of different NCO-terminated PU systems in a bulk process and without catalyst. Various PU systems containing increasing NCO/OH molar ratios were prepared. Siloxane precursors were then obtained after reaction of the NCO-terminated PUs with (3-aminopropyl)triethoxysilane, resulting in silane-terminated polymers. These structures were confirmed by different analytical techniques. Finally, four series of xerogels were prepared via a sol–gel process from the siloxane precursors, and their properties were evaluated depending on varying parameters such as the inorganic network crosslinking density. The final xerogels exhibited adequate properties in connection with biomedical applications such as a high in vitro degradation up to 15 wt% after 12 weeks.

Enhanced surface coverage of anchoring quaternary ammonium salts (AQAS) on oxygen-plasma treated quartz substrates

Oxygen plasma treatment was applied to atomically flat quartz surfaces in order to study the effect of surface activity on the adsorption of a silyl anchored quaternary ammonium salt biocide. Reduction of contact angle of the quartz surfaces were achieved from 72° to between 14° and 20° by applying oxygen plasma at increasing power between 100 W and 500 W. XPS analysis of the plasma-treated quartz surfaces indicated an increase in the presence of oxygen, implying the conversion of quartz surface siloxane groups into surface hydroxyl groups, consistent with the reduction in contact angle. Surfaces were examined by AFM after adsorption of silyl anchoring quaternary ammonium salts (AQAS). The surface profile of samples indicated an increase in the thickness of the adsorbed AQAS layer from 2.9 ± 0.1 nm for pristine quartz surfaces to 19.0 ± 2.0 nm for oxygen plasma treated surfaces, which is approximately the vertical dimension of 6 oriented molecular layers. The covalently bonded AQAS layer on the quartz surface exhibits a discontinuous film structure consisting of micro-zones of AQAS layers separated by voids or gaps, defined as regions on the quartz surface free of bound AQAS layers. These zones and voids are a consequence of the varying hydrophilicity/adsorption capability of the quartz surface. Plasma treated surfaces also showed a 3-fold reduction of void dimension from 3 µm to 1 µm between the AQAS adsorbed zones on the quartz slide owing to the increased hydrophilicity and adsorption capability of the surface. A leaching study of the AQAS adsorbed-quartz surfaces resulted in the reduction of film thickness from 19.0 ± 2.0 nm to 8 ± 1.0 nm. This reduction indicates the removal of some loosely bound outer layers, but confirms the retention of the surface-anchored layer of AQAS as well as a second and perhaps third layer adsorbed on the anchored first layer. • Oxygen plasma treatment increases surface hydrophilicity of quartz surfaces. • Reduced contact angle of quartz due to conversion of surface siloxane groups into surface silanol groups. • AFM shows increased adsorption of AQAS and multilayering (19 nm ~6 molecular layers) on plasma treated quartz surfaces. • Leaching studies indicate removal of loosely bound higher AQAS layers, but retention of surface anchored AQAS layers.

Polydimethylsiloxane containing waterborne hydrophobic polyurethane coatings with good adhesion to metals: Synthesis and characterization

Waterborne polyurethanes (WPU) are of great importance in the industrial field as adhesives and coatings due to the reduced use of organic solvents in their formulations. However, one of the main drawbacks of these formulations is their high hydrophilic character, so in this work siloxane groups were introduced into the soft segment in order to solve this problem. Thus, the synthesis of polyurethane dispersions with different proportions of the polyols (poly-ε-caprolactone (PCL) and polydimethylsiloxane (PDMS)) was carried out following the acetone process in three stages: polyurethane synthesis, water dispersion of the polymer and acetone removal. The reactions were monitored by Infrared Spectroscopy (FTIR) and the particle size was determined by Dynamic Light Scattering (DLS). Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Size Exclusion Chromatography (SEC), and Proton Nuclear Magnetic Resonance (1H NMR) were used to characterize the polyurethanes. Finally, after coating the dispersions onto metal substrates, adhesion strength, contact angle and phase morphology were studied. The introduction of siloxane as soft segment increased the surface roughness and hydrophobicity but did not change the adhesion values.

Acaricide activity of organo-modified siloxane and acaricide associations in Rhipicephalus microplus.

Search to a new alternative to control bovine ticks (Rhipicephalus microplus), the present study aimed to evaluate the acaricidal activity of organo-modified siloxane alone and in association with different commercial products or with piperonyl butoxide (BPO). Engorged females were subjected to an in vitro immersion test and 10 groups were used: control, 0.5% siloxane, 1% siloxane, 2% siloxane, 0.5% siloxane + 5% BPO, 1% siloxane + 5% BPO, 2% siloxane + 5% BPO, commercial product, 0.5% siloxane + commercial product, and 1% siloxane + commercial product. After immersion, engorged females were incubated for 14days for oviposition and hatchability tests. Another immersion test was performed with 5% siloxane and 2.5% siloxane + 10% BPO to evaluate the histopathological changes. Then, engorged females were incubated for 0, 2, 4, 8, 12, 24, 36, 48, 60, 72, 84, 96, 120, 144, and 168h and immersed in 10% formaldehyde for later analyses. The unassociated siloxane showed an acaricide efficacy of 93.88% at 2% concentration, and when associated with 5% BPO, it reached 100% efficacy at all tested concentrations. The tested commercial products showed enhanced efficacy when associated with siloxane. Histopathological analysis showed cell changes in both treatments and total cell disintegration after 120h in the 5% siloxane group and after 96h in the 2.5% siloxane + 10% BPO group. Therefore, siloxane alone or in combination is an alternative against R. microplus, and siloxane enhances the efficacy of available commercial products.

Maize Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and Its Application

Nowadays, silica gels have developed a lot of interest due to their extraordinary properties and their existing and potential applications in science and technology. Silica gel has a lot of applications such as a desiccant, as a preservation tool to control humidity, as an adsorbent, as a catalyst and as a catalyst support. Silica gel is a rigid three-dimensional network of colloidal silica, and is classified as: aquagel, xerogel and aero-gel. Extraction of amorphous silica from Maize Husk Ash (MHA) was carried out in this study. Silica xerogel was produced by dissolving MHA with alkali solution to form sodium silicate solution and lowering the pH to7 by adding hydrochloric acid to form silica aquagel followed by drying to form silica xerogel. The silica xerogel was characterized using SEM, XRD and FTIR techniques. Silica and mineral contents of MHA and xerogel were determined by EDS, X-ray diffraction patterns revealed amorphous nature of extracted silica. Fourier transform infrared (FTIR) data indicates the presence of siloxane and silanol groups. Silica yield from MHA was 56.32% while moisture content was 2.89% and also the SEM presented appropriated morphological characteristics of the best silica. MHA proved to be a potential low cost raw material for the production of silica gel. Keywords: Maize husk ash, amorphous silica, xerogel, surface properties DOI: 10.7176/CMR/13-3-01 Publication date: October 31 st 2021

Fabrication and application of icephobic silicone coatings on epoxy substrate

In winter, when the trains run at high speed, snow that falls on the track is easily drawn onto the bottom of the train, and quickly forms ice. Such icing may cause serious safety issues. In this paper, the epoxy resin is used as a primary coat and a hydroxyl-terminated silicone oil (PDMS) was coated on it. Siloxane, with amido or epoxy terminal group, named KH 550 or KH 560, respectively, was used as a co-crosslinking agent of the epoxy and PDMS in order to ensure high adhesive strength between the two layers. The hydrophobic, icephobic and mechanical properties of the coatings were characterized by contact angle measurements, ice-adhesion tests and tensile tests, respectively. The results show that the contact angle of the PDMS coating crosslinked by the KH 550 reaches 114.1°, and it can still show good hydrophobic properties after being immersed in water for 10 days. The adhesive strength of the ice on the PDMS coating is only 2.5% of that of ice on the epoxy coating. The low surface energy and the low elastic modulus should be responsible for the excellent icephobic properties. Moreover, the bonding force between the PDMS coating and the epoxy primer is also excellent. When the KH 560 was used as the co-crosslinking agent, the hydrophobic and icephobic properties of the top PDMS coating were improved due to its week polarity compared with KH 550. This study will be helpful in resolving the problems associated with the running of high speed trains in winter or the electric power system which requires resistance to freezing rain.

Preparing Nanosilica Particles from Rice Husk Using Precipitation Method

Nanosilica was extracted from rice husk, which was locally collected from the Iraqi mill at Al-Mishikhab district in Najaf Governorate, Iraq. The precipitation method was used to prepared Nanosilica powder from rice husk ash, after treating it thermally at 700°C, followed by dissolving the silica in the alkaline solution and getting a sodium silicate solution. Two samples of the final solution were collected to study the effect of filtration on the purity of the sample by X-ray fluorescence spectrometry (XRF). The result shows that the filtered samples have purity above while the non-filtered sample purity was around The structure analysis investigated by the X-ray diffraction (XRD), found that the Nanosilica powder has an amorphous structure in nature. Also, it shows a broad peak at ( The particle size distribution was determined by Atomic force microscope (AFM), the results gave that the average diameter equals and dimension range in , while B.E.T. analysis confirms a high surface area around 618 . FT-IR Spectra experimental data showed the presence of hydrogen-bonded silanol group (Si–O–H) and siloxane group (Si–O–Si) which proved the high purity of Nanosilica particles.

Structural and Electrical Properties of Silica Materials from Rice Husks

This study aimed to analyze the structural and electrical properties of silica from rice husks recovered by the process of ashing on a medium-scale furnace with a capacity of 15 kg. Rice husks were burned at a heating rate of 1.5°C/min to a temperature of 900°C, where the temperature was retained for 1 hour each at 400°C and 900°C. The methodology of this research was conducted through the process of ashing, extraction of silica, and characterization of its structural electrical properties. The silica extracted from rice husk ash had a relatively low water content by the low absorption intensity of the group –OH at 3610 cm-1. The silica was dominated more by the siloxane group (Si-O-Si) compared with the silanol group (Si-OH). Based on XRD analysis, the silica structure was confirmed as tetragonal. The silica also had a decreased resistance, impedance, and inductance as the frequency increased. These results indicate that the obstacles contained in silica content decrease with an increase in frequency. The decreasing of dielectric constants was caused by the frequency affecting the capacitance; i.e., increased frequency caused more waves to be transmitted each second. The electric current was turned before the capacitor plate was fully charged, which caused quick charge drainage in the capacitor plate and therefore reduced the ability of a material to store the electric charge.

Magnetically separable mesoporous alginate polymer beads assist adequate removal of aqueous methylene blue over broad solution pH

Adsorption is a promising technology for removal of organic and inorganic contaminants from soil and water system. In this study, magnetically separable mesoporous polymeric beads (NiZnFe4O4-HNT@alg) were synthesised for efficient removal of methylene blue (MB, cationic dye) under broad solution pH (from pH 3.41 to pH 8.43). Alginate biopolymer were used to stabilize halloysite nanotubes (HNTs) and nickel zinc iron oxide nanoparticles (NiZnFe4O4 < 100 nm). NiZnFe4O4 was incorporated onto the polymer beads to generate the adsorbents' magnetic properties and catalytic degradability. The adsorbent (NiZnFe4O4-HNT@alg) have higher surface area (122.43 m2/g), suitable mesoporosity (~6.68 nm), larger pore volume (0.11 cm3/g), and abundance of active sites, enabling high adsorption capacity (264 mg/g) of MB. The abundance of hydroxyl, carboxyl, and siloxane groups enabled cationic dye sorption through ionic interaction. The removal efficiency of MB was ~99% under a wide solution pH range from 10 mg/L of MB, in which the adsorbent dose was 2 g/L. Both Langmuir (R2 = 0.99; p < 0.001) and Freundlich (R2 = 0.99; p < 0.001) isotherm models fitted well, whereas trends of kinetics model fitting are pseudo-second-order (R2 = 0.99) > intraparticle diffusion (R2 = 0.93) > pseudo-first-order (R2 = 0.87). Energy-dispersive X-ray spectroscopy (EDS) elemental mapping demonstrated that MB has a co-distribution with silicon, aluminium, and alginate carbon phase but is limited with iron and nickel, indicating HNTs and alginate polymer performed as sorption sites, whereas NiZnFe4O4 performed as a catalyst. The presence (post-sorption) and absence (pre-sorption) of inorganic, total carbon or total organic carbon content at different solution pH, contact time, and initial concentration of MB demonstrated that the adsorbent act as a catalyst as well for degradation of MB. NiZnFe4O4-HNT@alg triggers efficient removal of MB with the assist of adsorption and catalytic degradation at broad solution pH. A comparison in removal of MB by various adsorbents including, biochars, clays, activated carbon, nanoparticles, polymers, nano composites, graphene oxides, carbon nanotubes, and polymer beads with the result of this study were performed, illustrating competitive sorption capacity of NiZnFe4O4-HNT@alg.

Synthesis of Comb-Polyurethane-Modified Polycarboxylate at Indoor Temperature and Its Interaction With Portland Cement

According to the principle of radical polymerization reaction, different polycarboxylates with comb structures were synthesized. With the other two commercial polycarboxylates (C-PCE-1 and C-PCE-2), the effects of all the polycarboxylates on adsorption, hydration, zeta potential, liquid surface tension, and flowability in Portland cement were determined. Compared to O-PCE and C-PCEs, the adsorption value of M-PCE increased by 14.1% and the adsorption rate increased by 24% maximum. O-PCE, C-PCE-1, and C-PCE-2 have a delayed effect on the hydration of the cementitious materials, but M-PCE does not. Due to higher adsorption amount, M-PCE with siloxane groups has an excellent comprehensive performance of zeta potential, liquid surface tension, and flowability in cementitious materials.

Sustainable Thermochemical Extraction of Amorphous Silica from Biowaste

The objective is to utilize zero wastage rice hull material which contains silica as a major component in amorphous form and is used as reinforcement material for various applications. Burning of rice hull (RH) under controlled condition after removal of metal ions leads to white silica of high purity. An inexpensive method for extraction of amorphous silica by thermochemical treatment (pyrolysis process) is performed. Pyrolyzed biomass at four different temperatures is observed for treated and untreated rice hull. Calcination of the rice hull at 600ºC in a muffle furnace turns it into white amorphous silica. In this research, HCl was used to retrieve silica from the rice hull. Extracted silica was characterized by X-ray diffraction analysis, which indicates that the silica is in amorphous form, and displayed a strong broad peak at 22.32º and 21.52˚ (2θ). The FTIR data revealed the existence of peaks at 4000 cm− 1& 400 cm− 1 showing the presence of siloxane and silanol groups. UV-Visible (absorption) band maxima was demonstrated at 367 nm, photoluminescent (emission) spectra displayed a short peak at 453 nm and a sharp intensity peak at 488 nm is comparable with amorphous nano-silica. Less amount of silica appeared at the inner surface of rice hull fiber revealed by SEM analysis. Other element traces were absent, high purity of amorphous silica is observed by EDS.

A comparative study of superhydrophobicity of 0D/1D/2D thermally functionalized carbon nanomaterials

Superhydrophobic coatings promise various practical applications. A one-step, ingenious yet economical thermal curing method is devised to render the carbon nanomaterials superhydrophobic. This study aims to compare the degree of superhydrophobicity of the carbon/polydimethylsiloxane (PDMS) synthesized from the 2D graphene nanoplatelets (GNPs), 1D multiwalled carbon nanotubes (MWCNTs), and 0D carbon black (CB) nanomaterials. The superhydrophobic GNPs/PDMS, MWCNTs/PDMS and CB/PDMS are synthesized when thermally functionalized with the siloxane groups. The Fourier transform infrared spectroscopy data signifies the successful functionalization of the carbon nanostructures by siloxane chains and the Raman spectroscopy analyses indicate that GNPs/PDMS manifests the highest degree of structural defects due to functionalization. The degree of superhydrophobicity induced on the carbon/PDMS coatings correlates with the dimensions of the carbon nanomaterials (0D, 1D and 2D), which is intimately associated with the effective surface areas of the nanomaterials susceptible of chemical functionalization. The promising applications of the superhydrophobic coatings are demonstrated. This study proposes a novel wettability tuning method and provides insightful analyses and characterization of the superhydrophobicity of the thermally functionalized carbon nanomaterials with different dimensions of varied nano-geometries.

Mesoporous Biopolymer Architecture Enhanced the Adsorption and Selectivity of Aqueous Heavy-Metal Ions.

Halloysite nanotubes (HNT) and ball-milled biochar (BC) incorporated biocompatible mesoporous adsorbents (HNT-BC@Alg) were synthesized for adsorption of aqueous heavy-metal ions. HNT-BC@Alg outperformed the BC, HNT, and BC@Alg in removing cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb). Mesoporous structure (∼7.19 to 7.56 nm) of HNT-BC@Alg was developed containing an abundance of functional groups induced from encapsulated BC and tubular HNT, which allowed heavy metals to infiltrate and interact with the adsorbents. Siloxane groups from HNT, oxygen-containing functional groups from BC, and hydroxyl and carboxyl groups from alginate polymer play a significant role in the adsorption of heavy-metal ions. The removal percentage of heavy metals was recorded as Pb (∼99.97 to 99.05%) > Cu (∼95.01 to 90.53%) > Cd (∼92.5 to 55.25%) > Ni (∼80.85 to 50.6%), even in the presence of 0.01/0.001 M of CaCl2 and Na2SO4 as background electrolytes and charged organic molecule under an environmentally relevant concentration (200 μg/L). The maximum adsorption capacities of Ni, Cd, Cu, and Pb were calculated as 2.85 ± 0.08, 6.96 ± 0.31, 16.87 ± 1.50, and 26.49 ± 2.04 mg/g, respectively. HNT-BC@Alg has fast sorption kinetics and maximum adsorption capacity within a short contact time (∼2 h). Energy-dispersive X-ray spectroscopy (EDS) elemental mapping exhibited that adsorbed heavy metals co-distributed with Ca, Si, and Al. The reduction of surface area, pore volume, and pore area of HNT-BC@Alg (after sorption of heavy metals) confirms that mesoporous surface (2–18 nm) supports diffusion, infiltration, and interaction. However, a lower range of mesoporous diameter of the adsorbent is more suitable for the adsorption of heavy-metal ions. The adsorption isotherm and kinetics fitted well with the Langmuir isotherm and the pseudo-second-order kinetic models, demonstrating the monolayer formation of heavy-metal ions through both the physical sorption and chemical sorption, including pore filling, ion exchange, and electrostatic interaction.