Industrial waste water containing organic pollutants is a universal issue due to its hazardous chemical nature. Fabrication of hybrid mixed-matrix is a typical and powerful approach to create new ...functionalities that cannot be represented by single-phase materials. In present study, we have reported the in-situ growth of zeolite imidazolate frameworks (ZIF-67) on layered double hydroxides (LDH) to form porous composites to develop materials for removal of methylene blue (MB) and methyl orange (MO). Scanning electron spectroscopy showed a sandwich like structure of composite decorated with polyhedrons of ZIF-67. For comparative studies, ZIF-67 and CoAl-LDH were also synthesized and used for adsorptive removal of MB and MO dyes. Results showed that ZIF-67@CoAl-LDH has good adsorption capacity (qm, 57.24 mg g−1) for methylene blue as compared to LDH (15.04 mg g−1) and ZIF-67 (57.14 mg g−1). Furthermore, ZIF-67@CoAl-LDH also showed good adsorption capacity (qm 180.5 mg g−1) for methyl orange than LDH (32.27 mg g−1) and ZIF-67 (75.58 mg g−1). Also, with 100 min contact time 79.9% MB and with 90 min contact time 72.3% MO was adsorbed by ZIF-67 and it's composite. The equilibrium adsorption data were well fitted by Langmuir model and relatively high correlation coefficient of Langmuir model (R2 = 0.9953 ZIF-67 and 0.9889 ZIF-67@CoAl-LDH) for MB and (R2 = 0.9917 ZIF-67 and 0.9737 ZIF-67@CoAl-LDH) for MO suggesting a mono-layer adsorption of MB and MO on the ZIF-67 and its composite. Further, the ZIF-67 and its composite (ZIF-67@CoAl-LDH) exhibited no obvious loss in MB and MO removal after recycling for four times. The overall results indicate that the as-prepared ZIF-67 and its composite are efficient for removal of dye pollutants containing methylene blue and methyl orange form water.
•Surficial induced growth of ZIF-67 on Co-layered double hydroxide.•Highly modest and fast route for efficient removal of dyes.•The superior activity attributed to metal nodes and accessible coordinately unsaturated sites.
In this work, LDH-biochar composites were synthesized in different molar ratios of Mg:Al (2:1, 3:1 and 4:1) using co-precipitation method. The composites were applied to remove an organic dye from ...aqueous solutions by adsorption. The composites and the pure bovine bone biochars were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements, thermogravimetric analysis (TG/DTG), dispersive energy spectroscopy (DES) and scanning electron microscopy (SEM). The methylene blue dye adsorption experiments were conducted in a finite bath. The results indicate that pH 12 is more suitable for dye adsorption process, with a removal >95% for all composites. The adsorption kinetic was best described by the pseudo-second order model, reaching the equilibrium in approximately 20 min. The Redlich-Peterson model fit the adsorption equilibrium isotherms satisfactorily. It was obtained a maximum adsorption capacity of 406.47 mg·g−1 at 40 °C. Negative values of ΔG indicate the spontaneity of the adsorption process. The positive value of ΔH (30.72 kJ·mol−1) indicates the physical nature of the adsorption and the positive value of ΔS (0.1863 kJ·mol−1) indicates that there was a change in the structure of the adsorbent and increased randomness during the fixing of the dye.
•A novel adsorbent, LDHs-biochar composite, were satisfactory synthesized.•A great adsorption capacity of 406.47 mg·g−1 was obtained to remove methylene blue.•In 20 min the adsorbent remove 95% of the dye from water.•The adsorption was spontaneous, endothermic and provide changes in the material structure.
Primary alkylammonium cations with progressively increasing chain length from methylammonium (CH3-NH3+) to nonadecylammonium (CH3-(CH2)18-NH3+) were used to prepare unique series of ...organo-montmorillonites (O-Mts). Infrared spectroscopy in the mid-IR and near-IR regions and XRD were used to characterize samples and to investigate the effect of the chain length on the arrangement of cations confined in montmorillonite (Mt) interlayers. For the first time detailed assignment of the vibration bands in the near-IR region (8000–4000 cm−1) was provided not only for O-Mts but also for selected primary alkylamines and alkylammonium salts, used for their preparation. The IR spectra showed that both, type of head-group, i.e. NH2 vs NH3+, and nature of the anionic counterpart, i.e. chloride vs Mt layer, significantly affected the positions the NH vibration modes as a result of different H-bonds in O-Mts. The alkyl chain length had significant effect on the arrangement of the intercalated cations. With increasing chain length the stretching (νCH2) and first overtone (2νCH2) bands were shifted to lower wavenumbers indicating decreasing amount of disordered gauche in favor of ordered all-trans conformers. Significantly higher shift of the 2νasCH2 band than νasCH2 benefits the NIR region for conformational studies more than MIR.
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•Organoclays were prepared from montmorillonite and primary alkylammonium cations.•NIR spectroscopy provides new insight into the structure of intercalated surfactants.•Type of head-group and anionic counterpart affect the NH vibration modes positions.•With increasing length of alkyl chain the surfactants adopt more ordered conformation.
Traditional homogeneous Fenton reactions can only be carried out under acidic conditions; however, visible light can greatly enhance the activity and stability of iron-doped semiconductor catalysts ...in the Fenton system. Therefore, in this study, a commercially applicable Fe/graphitic carbon nitride (g-C3N4)/kaolinite composite photocatalyst was prepared for the first time using an in-situ calcination process. The results showed that Fe ions and g-C3N4 were successfully loaded onto kaolinite with a two-dimensional uniform sheet structure. The as-synthesized Fe/g-C3N4/kaolinite composite containing 0.9 mmol of Fe (Fe/CN/K-0.9) showed a degradation efficiency of 89% for tetracycline hydrochloride (TCH) within 80 min in the photo-Fenton system. Compared with photocatalytic degradation (29.6%) and Fenton degradation (76.6%), a photo-Fenton degradation efficiency of 85% was maintained after three cycles. Free radical scavenging experiments also showed that hydroxyl radicals were the main active substances. The enhanced photocatalytic activity of the composite was attributed to the large specific surface area of kaolinite, which could effectively adsorb TCH. Furthermore, FeIII acted as a photo-generated electron acceptor, which not only avoided photo-generated electron-hole recombination but also effectively reduced the consumption of H2O2 to realize a stable FeII/FeIII cycle reaction, thus improving photo-Fenton catalytic activity.
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•A kaolinite composite photocatalyst was prepared using in-situ calcination process.•Kaolinite can significantly improve the adsorption performance of g-C3N4.•Fe3+ can act as a photo-generated electron acceptor.•The photo-Fenton reaction mechanism for the kaolinite composites was proposed.
Excessive use of nitrogenous fertilizers has led to increased nitrate concentrations in groundwater that pose a threat to human health, via nitrate-contaminated potable water, and contribute to ...eutrophication. The elimination of nitrate from water systems has been thoroughly examined; however, unconventional and low-cost technologies are greatly needed. Clays and clay minerals are widely-used for environmental applications, mostly due to their non-toxicity, worldwide abundance, low cost and physicochemical properties (high surface area, ion exchange capacity, high sorption and catalytic properties). Most are used for the degradation of cationic pollutants, nevertheless, they can be equally efficient at anionic decontamination, depending on the modification process they have undergone, or the materials they are combined with. This review aims to assemble the available literature research on the application of clays and clay minerals as well as the mechanisms that lead to successful removal of nitrate from water. The main characteristics of clays and clay minerals in nitrate uptake are evaluated and the known shortcomings of their application discussed, leading to suggestions for further research.
•Unmodified clay minerals and clays may present low AEC for NO3−.•Clay minerals and clays show enhanced AEC for NO3− after modification processes.•NO3− adsorption or reduction via clay-based composites is state of the art.•Fe nanoparticles or electroreduction/clay minerals reach the highest NO3−removal.•Methods' cost estimation and pilot scale applications lack from bibliography.
Water is considered ubiquitous within the shale reservoirs and mainly stored in the hydrophilic clay minerals. The water distribution characteristics and its effect on pore structure are important ...for the gas-in-place of shale systems. In this work, water vapor adsorption on montmorillonite (Mt), kaolinite (Kaol) and illite (Il) were performed to investigate the behaviors of water adsorption on shale clay. Subsequently, the moisture-equilibrated samples were conducted with N2 gas-adsorption techniques to investigate the effect of adsorbed water on pore structure characteristics, such as apparent pore size distribution (APSD), N2 BET specific surface area (N2-BET SSA) and pore volume (PV). The results show that the water uptake isotherms of our samples have the sigmoidal-shaped profiles and GAB model provides a good fit for the adsorption behavior. In addition, The APSD curves under different relative humidity (RH) conditions have validated the condensation effect and indicated that the small pores (approximately smaller than 5nm) are blocked by the capillary water and will disappear on the APSD curves at RH of 98% while the large nanopores (>5nm) are covered with water film, these effects will lead dramatically decrease of N2-BET SSA. Taking Mt and Il samples as the examples, the N2-BET SSA has declined to 33.51% and 33.66% compared with the dry conditions when Sw approaches to 50%. Meanwhile, these effects also indicate that the gas storage for clay minerals is massively overestimating under dry condition, the contribution to methane adsorption might be negligible in the actual shale reservoir.
•Water adsorption isotherms were applied to investigate the adsorption behaviors of water vapor on clay minerals.•APSD curves were measured with N2 gas-adsorption techniques to validate capillary condensation in small pores.•The water distribution is visually presented by comparing the APSD curves between dry and moist condition.•The impact of water on pore structure characteristics and methane adsorption capacity are analyzed.
This work concerns the application of single and mixed pillared clays in adsorption of inorganic pollutant in the water: the cadmium, the cobalt, and the copper. Adsorption experiments were conducted ...under various conditions, i.e., pH, contact time, initial concentration, and temperature. A comparison of the adsorption of the three metals onto pillared clays and natural clays suggested that pillared clays had higher adsorption affinity for metals than the unpillared clays. The experimental results indicated that the pillared clays rich on cerium show better properties on Cd2+, Co2+, and Cu2+ adsorption than those without cerium, which made them the promising recycling metals adsorbents. The equilibrium isotherm data were analyzed using the Langmuir and Freundlich isotherm equations. In all cases, the adsorption process fitted the second-order kinetics well, and the isotherm equation due to Langmuir showed good fits with the experimental data.
•Single (Zr-PILCs and Al-PILC) and mixed Zr/Al-PILC, CeZr-and/or Al-PILC have been prepared.•Samples were used as adsorbent for the cadmium, cobalt and copper removal.•The temperature, initial metal concentration, and pH affects the adsorption capacity.•Ce-Zr−PILC and Ce-Zr-Al-PILC show superior adsorption capacity.
Heterogeneous photocatalysis is an efficient, economical and environmentally friendly technology for removing organic contaminants from the aqueous environment. Titania is one of the most popular ...photocatalyst for decomposing organic compounds due to its strong photocatalytic activity, chemical and biological inertness and high photochemical stability. Extensive literature analysis has shown many possibilities to improve the efficiency of photodecomposition of organic compounds over TiO2. Clay minerals with large surface areas for adsorption and high adsorption capacity used to synthesize nanocomposites with TiO2 (especially anatase) enhance the decomposition of organic pollutants by photocatalytic degradation. Recently, clay minerals have been used more often to prepare hybrid photocatalysts. Dispersing TiO2 nanoparticles onto the surfaces of clay minerals improves the photocatalytic activity of TiO2 by providing more active surface sites and reducing the agglomeration of TiO2 particles. The present review paper offers the following: an overview of the trend in the use of the clay/TiO2 nanocomposite photocatalysts, especially halloysite/TiO2 materials for removal of organic contaminants from water, report on the recent work done and important applications for photocatalytic degradation of organic pollutants.
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•Titanium dioxide as one of the most popular photocatalyst for decomposing organic compounds.•The use of the clay/TiO2 nanocomposite as photocatalysts during photodegradation of organic contaminants.•Halloysite as an attractive support for TiO2 nanoparticles.
The present communication addresses the removal of toxic lead, cadmium, and arsenic using iron oxide modified clay-activated carbon composite beads from aqueous solutions. The SEM-EDX analysis was ...conducted to study the heterogeneity of the surface and the elemental composition of the composite beads. The specific surface area of the composite beads was found to be 433 m2/g. Furthermore, the XRD pattern indicates the intercalation of iron particles between the layers of bentonite clay. The FT-IR analysis suggests that the hydroxyl, carboxyl, and Fe-O were the major functional groups responsible for the removal of lead, cadmium, and arsenic. The Langmuir monolayer sorption capacity of Pb(II), Cd(II) and As(V) were observed to be 74.2, 41.3 and 5.0 mg/g respectively. Kinetic studies indicate that intra-particle diffusion plays a significant role in the removal of these three toxic pollutants. In addition, the composite beads were applied for the adsorption of a ternary mixture of subjected pollutants at low concentrations and found efficient to remove these pollutants up to an acceptable permissible limit of drinking water. The significances of this study propose the potential of composite beads for purifying the water containing toxic pollutants, viz., lead, cadmium, and arsenic.
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•Reasonable preparation of Fe-modified bentonite-activated carbon alginate beads•Beads enhance the handling efficiency and applied as a multifunctional adsorbent•Developed beads showed better sorption efficiency for single and mixed toxic ions•Maximum sorption efficiency for Pb(II):74.2, Cd(II):41.3 and As(V):5.0 mg/g beads•Molded adsorbent for trace level toxic ions removal from ternary mixture system.
The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS ...curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study the rotational mobility of Hal. From the obtained rotational diffusion coefficients of the different Hal we deduced their length via the Broersma theory, which compares well to TEM data. The analysis of both SANS and EBR data provided a bulk average information on the Hal structure in water, which, for instance, documented the markedly higher degree of well-definedness of the PT-Hal and the thinner tube walls present here. The attained systematic structural knowledge represents a step forward for the robust structural description of halloysites selected from four geological deposits and shows that Hal of different origin differ very markedly with respect to their mesoscopic structure.
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