Calcined Hydrotalcite Research Articles

In‐Depth Analysis of the Complex Interactions Induced by Nanolayered Additives in PHBV Nanocomposites

AbstractNew nanocomposites based on biopolymer poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) are processed via extrusion, using low content of calcined hydrotalcite (CHT) and cloisite 20A (C20A) as additives (3 wt%). The aim of this work is to characterize the thermal and viscoelastic response of the structures induced by the presence of the additives. Field‐emission scanning electron microscopy and laser profilometry are utilized to analyze the effect of the additives on the surface finish of extrusion filaments, detecting a smoother surface induced by additives. A lower degradation temperature is observed via thermogravimetry for composite containing CHT (PHBV+3%CHT), while such a phenomenon is not present in composite with C20A (PHBV+3%C20A). An increase in crystallinity due to the nucleating effect of additives is measured via differential scanning calorimetry. The intercalation of the biopolymer in the layered structure of the additives is observed via X‐ray diffraction, reflecting the effective interaction in the composite matrix. The viscoelastic behavior of the samples is evaluated by means of rheology and dynamic‐mechanical analysis, showing a non‐Newtonian behavior and an enhancement of the vitreous state response. All results converge to the conclusion that the incorporation of the additives induces the formation of long‐term structures that present variable sensitivity to temperature and frequency.

Experimental Study and Numerical Analysis of Chloride Ion Diffusion in Hydrotalcite Concrete in Chloride Salt Environment.

Hydrotalcite, known as layered double hydroxides (LDHs), is a new type of admixture used to delay the corrosion of reinforcement. The aim of this study was to investigate the chloride ion diffusion behavior of C30 concrete with varying amounts of calcined hydrotalcite (0%, 2%, 4% and 6%) in a chloride salt environment. The NT-Build 443 test was adopted to characterize the one-dimensional accelerated chloride ion penetration of concrete. The distribution of chloride ion concentration in hydrotalcite concrete with different mix proportions immersed in sodium chloride solution for 30 days and 60 days was determined, and the chloride ion diffusion coefficient and surface chloride ion concentration were fitted based on Fick's second law to establish the chloride ion diffusion model considering the influence of multiple factors. This model was validated using COMSOL Multiphysics finite element software. The results show that concrete mixed with LDHs can meet its compressive strength requirements and that the resistance of concrete with 2% calcined hydrotalcite to chloride ion penetration is the best with a 19.6% increase in the 30-day chloride ion penetration coefficient. The chloride ion diffusion process under chloride salt immersion conditions is in accordance with Fick's second law. The chloride ion concentrations calculated with COMSOL software and the test results are in good agreement, which verifies the reliability of the chloride ion diffusion model.

Microstructure and interface analyses of novel external anode mortar incorporated calcined hydrotalcite nanoparticles towards an enhanced impressed current cathodic protection

BackgroundDuring Impressed current cathodic protection (ICCP), acidification around the mortar is occurred by anodic reactions including the transfer of hydroxide to oxygen, and significantly influences the expected lifetime of the utilized external anodes. MethodsIn this study, calcined hydrotalcite (CLDH NPs) were designed by a simple and single step and were presented to stabilize the pH around anode mortar in the ICCP system. The modified ICCP system by CLDH or its external anode was evaluated by surface, mechanical, and electrochemical analyses (impedance (EIS) and potentiodynamic polarization (PDP)) besides different techniques such as X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), and scanning electron microscope (SEM) morphology at the investigated anode mortar interface. Significant findingsThe obtained results indicated that CLDH NPs enhanced the lifetime of the external anode in ICCP by decreasing the acidification around the mortar. The corrosion current (Jcorr) went down from 1.78 to 1.62 µA/cm2 due to the CLDH NPs incorporation, which indicated the impact of CLDH NPs on the electrochemical stability of the utilized mortar. Besides, the presented CLDH NPs could potentially be applied for the engineering fabrication of the anode mortars in ICCP systems.

Reduction of carbon dioxide to dimethylformamide using ruthenium doped Mg/Al hydrotalcites under supercritical conditions

The utilization of carbon dioxide is one of the developing areas due to its significant contribution to global warming. Reducing carbon dioxide (CO2) to formic acid and its derivatives has gained importance because of its thermodynamic limitations and high industrial demand. In this article, we report the synthesis of dimethylformamide (DMF) using ruthenium doped Mg/Al calcined hydrotalcite by CO2 hydrogenation in the presence of dimethylamine (DMA). At optimized conditions, complete conversion of dimethylamine was achieved with more than 92% product yield at 170 °C and 13 MPa pressure with a reaction time of 6 h. Key catalyst properties were determined using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), CO2-temperature programmed desorption (TPD), H2 temperature-programmed reduction (TPR) and Fourier transform infrared (FTIR). The determination of surface morphology was carried out using field emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). At the same time, the chemical composition was verified by energy-dispersive X-ray (EDS). In addition, kinetic modeling is performed using the two site Langmuir-Hinshelwood-Hougen-Watson model. The regressed kinetic parameters gave an appropriate fit with experimental concentration values and activation energy is calculated as 413 kJ/mol K−1.

Synthesis and evaluation of Mg-Al hydrotalcite formation and its influence on the microstructural evolution of spinel-forming refractory castables under intermediate temperatures

The mechanical properties of in-situ spinel (MgAl2O4)-forming alumina-based castables under intermediate temperatures are of critical importance before the refractory lining system reaches normal operating conditions. The objective of this study is to elucidate the role of the hydrotalcite formed within a fine-grained castables matrix, in which no strength loss of the MgO-bonded alumina-based castables without silica fume was observed. Numerous fundamental studies were conducted to examine the factors influencing hydrotalcite formation within the blended pastes composed of MgO and Al2O3 nanopowders; dead burned or fused magnesia and Al2O3 nanopowder; dead burned magnesia and water-dispersed sol of fumed alumina by using: XRD and DSC-TG-EGA(MS). The XRD, FTIR and 27Al MAS NMR analysis of the hydrotalcite calcination products revealed that the spinel begins to form at temperatures as low as 700 °C. Finally, the physical properties, phase composition and microstructure of the refractory castables bonded with the hydrotalcite decomposition-routed nanostructured spinel were evaluated.

Experimental investigations on concrete incorporated with calcined hydrotalcite under sea water curing

In this study, Calcined Hydrotalcite is used in concrete to facilitate seawater curing. The salts from seawater penetrate into the concrete which lowers the strength of the concrete when cured in sea water. Also, these salts attack the reinforcement of RC elements causing corrosion of steel. Hydrotalcite is a layered double hydroxide which resembles talc and has high water content. Calcined hydrotalcite has higher adsorption capacity and can be used for adsorption. Calcined hydrotalcite has been prepared by grinding method. It has been synthesised from Aluminium Oxide, Magnesium Hydroxide, and Sodium Bicarbonate by heating at 100 °C. The Calcined Hydrotalcite thus synthesised and added to concrete in proportions. Then, when this concrete has been cured in sea water, the anions in the seawater were adsorbed by the added calcined hydrotalcite. Thus, the strength of the concrete element is retained even when cured in sea water.

The Resistance of Novel Concrete Prepared by Gap-Graded Blended Cement under Chloride-Sulfate Attack

The resistance of concrete under chloride-sulfate attack dominates the durability of marine constructions. The binder played a more important role in chloride-sulfate resistance of concrete due to the dynamic hydration process. Incorporating supplementary cementitious materials (SCMs) was beneficial to the microstructure densification of cement paste, but the low hydraulic activities of SCMs resulted in the decrease of mechanical properties, activating activities of SCMs would raise the cracking risk of cement paste. On the basic of close packing theory, a gap-graded blended cement contained calcined hydrotalcite and metakaolin was adopted to prepare concrete with high resistance under chloride-sulfate attack in present study. The gap-graded blended cement concrete presented comparable strength with Portland cement concrete, even though only 25% clinker used in the blended cement. Because of the continuous hydration of alumina-rich SCMs and functional components, the secondary hydration products with high chloride binding capacity helped blocking ions ingress, resulting in the one-magnitude decrease of chloride diffusivity. At the early period of soaking duration in chloride-sulfate solution, the sulfate ions were beneficial to delaying the migration of chloride. And the cracks introduced by expansive products from sulfate attack would observably accelerate the release and continuous ingress of chloride at late period.

Approaches to enhance the carbonation resistance of fly ash and slag based alkali-activated mortar- experimental evaluations

Alkali-activated composites using by-products such as fly ash and slag have been widely studied to make greener construction materials. However, the carbonation of alkali-activated composites has been reported to induce cracking and corrosion of steel reinforcements in structural elements. This shortcoming has greatly limited the structural applications of alkali-activated composites due to durability concerns. This study aims at exploring possible approaches to enhance the carbonation resistance of fly ash and slag based alkali-activated mortar (AAM) by adding different additives, including calcined hydrotalcite (C-HT), calcium silicate (CS), gypsum and silica fume (SF), in the mix proportions. Various blend ratios of additives were considered in the series of laboratory investigations. After 28 d of curing, AAM specimens were subjected to accelerated carbonation condition with 1% CO2 concentration at 25 °C up to additional 56 d. The carbonation resistance was evaluated by examining the carbonation depths, followed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen (N2) adsorption/desorption tests for in-depth investigations. In addition, the workability of the fresh mortar and the compressive strengths at different ages were also considered for comprehensive evaluation of the feasibility in structural applications. According to the test results, it is found that the addition of C-HT is the most effective measure among the approaches considered in the present study in terms of improving the carbonation resistance and compressive strength, while assuring the workability of the mortar.

Interesterification of triglycerides with methyl acetate for the co-production biodiesel and triacetin using hydrotalcite as a heterogenous base catalyst

Biodiesel is a renewable fuel with several advantages over petro-based fuels and is conventionally produced by the transesterification of triglycerides with alcohols. Chemical interesterification of triglycerides is a good alternative as compared to transesterification, as it yields a value-added compound, triacetin, as a co-product instead of the already abundant commodity, glycerol. In this work, interesterification of soybean oil was carried out with methyl acetate to co-produce biodiesel and triacetin, using calcined hydrotalcite as a heterogeneous base catalyst. Several base catalysts were tested for this reaction. Calcined Mg-Al hydrotalcite (Mg:Al mole ratio – 3:1) was found as the best catalyst for achieving 95.9 % conversion of soybean oil triglycerides in 4 h and yielding 5.3 % selectivity of triacetin along with the value-added intermediates - monoacetindiglycerides and diacetinmonoglycerides, produced with a selectivity of 46 % and 48.7 %, respectively. The optimum reaction conditions were found at an oil to methyl acetate mole ratio of 1:50, catalyst loading of 0.04 g/cm3 and a temperature of 200 ºC. The catalysts were fully characterized before and after the reaction, and were found to possess high surface area with both basic and acidic sites. The effect of various reaction conditions on the rate of reaction, conversion of triglycerides and selectivity of triacetin were studied. The concentration profiles of the reactants, intermediates and products obtained at different temperatures were used to obtain the kinetic rate constants and the activation energy of each parallel step was evaluated. Reusability studies showed that the catalyst was stable and reusable up to three cycles.

Calcination of hydrotalcite to enhance the removal of perfluorooctane sulfonate from water

Perfluorinated compounds (PFCs), due to their thermal and chemical stability and broad usage in industry, have been detected in surface and ground water. As emerging compounds, their fate in the environment and removal from water attracted great attention in the last 10 years. In this study, we evaluated the performance of calcinated hydrotalcite (CHT) for the removal of PFCs using perfluorooctane sulfonate (PFOS) as an example. Our results showed that CHT can sorb up to 1.4 times of its mass for PFOS and the removal was fast, with equilibrium being achieved in 30 min. The PFOS removal was less sensitive to pH in pH 4–11 range. At low loading levels, only small fractions of CHT were intercalated by PFOS and the 3R polytype of hydrotalcite (HT) was largely maintained. As the PFOS uptake increased beyond 300 mg/g, intercalation of PFOS took place. The structure of HT changed to 1 layer stacking beyond 600 mg/g. Electrostatic interaction was responsible for the PFOS uptake at low loading levels and hydrophobic interaction started to play a role among PFOS molecules as its loading level increased. Crystalline PFOS decomposed at 513 °C, but its decomposition temperature decreased to 443 °C once sorbed on CHT, due to the breakdown of HT at about 390 °C. The CHT was regeneratable after calcination of PFOS-saturated HT at 450 °C for 3 h with the full PFOS removal capacity restored. The finding from this study showed the superior feature of using CHT for the removal of PFCs over other methods.

Immobilization mechanism of Se oxyanions in geopolymer: Effects of alkaline activators and calcined hydrotalcite additive

Geopolymers have been widely adopted to stabilize the cationic pollutants. However, few studies have focused on the immobilization of anionic species. In this study, the immobilization of SeO32– and SeO42– was explored for the first time using geopolymer activated by different alkaline solutions (NaOH and Na2SiO3) with and without calcined hydrotalcite (CHT), characterized by TCLP, XRD, FTIR, TG, NMR, XAFS, and N2 adsorption-desorption isotherm. Na2SiO3-activated geopolymers without CHT additive showed lower leaching percentages of SeO32– and SeO42– (approximately 10 % and 18 %) than NaOH-activated geopolymers (approximately 58 % and 74 %). It has been proven that electrostatic interaction is the main association mode of SeO32– and SeO42– in both NaOH- and Na2SiO3-activated geopolymers. Hence, compactness plays a vital role in the Se leaching from geopolymer. The addition of CHT reduced the compactnesses of both NaOH- and Na2SiO3-geopolymers. Due to the formation of hydrotalcite, the CHT additive contributed to immobilize SeO32– and SeO42– in NaOH-activated geopolymers. However, this phenomenon was not observed in Na2SiO3-activated geopolymers. Thus, the leaching amount of Se greatly increased from Na2SiO3-activated geopolymers with CHT additive. This study provides new insights on the application of geopolymer to immobilize anionic pollutants.

Pd–Co Nanoparticles Supported on Calcined Mg–Fe Hydrotalcites for the Suzuki–Miyaura Reaction in Water with High Turnover Numbers

We reveal the Suzuki–Miyaura reaction catalyzed by a Pd–Co nanocatalyst supported by Mg–Fe–CHT (calcined hydrotalcites). A variety of boronic acids and aryl halides were transformed into functionalized biphenyls in excellent yields using water as a solvent. The reaction could proceed under mild conditions with a simple operation and high turnover numbers. The excellent catalytic activities are reasonably attributed to the Co-doping, which forms a Pd–Co alloy on the surface of CHT.

Structure and CO2 physisorption capacity of hydrotalcite-derived oxide

Understanding the atomic structure and the corresponding adsorption mechanism of CO2 adsorbents is the key to develop efficient CO2 adsorption materials. Here, we studied hydrotalcite-derived oxides or layered double oxides (LDOs), one of the most promising candidates for the inexpensive and effective CO2 adsorption in the intermediate temperature regime, using atomistic simulation techniques. We first constructed the equilibrium structure of an LDO and showed that this oxide was crystalline with an MgO-like structure. In particular, Mg ions configured with the FCC arrangement of oxygen ions and most of the Al3+ ions occupied octahedral positions by substituting Mg2+ ions and the rest (∼10%) occupied the tetrahedral positions. We then compared the CO2 physisorption properties of the amorphous and crystalline LDOs that respectively represented LDOs form at lower and higher limits of hydrotalcite calcination. Static and dynamic adsorption analyses revealed that the amorphous LDO had overall higher physisorption capacity. CO2 molecules exhibited a random arrangement in the adsorption layer of the amorphous LDO but an ordered arrangement in the case of crystalline LDO. As a result, CO2 molecules were able to adsorb to and to desorb from the amorphous LDO surface dynamically while the stable adsorption layer near the crystalline LDO surface acted like a contamination preventing other CO2 molecules to adsorb, thereby lowering the overall adsorption capacity of the crystalline LDO. Depending on the level of crystallinity, the physisorption behavior of the mixed oxide forming during the hydrotalcite calcination is expected to change between two structures studied here.

An Investigation into the Effect of Hydrotalcite Calcination Temperature on the Catalytic Performance of Mesoporous Ni-MgO-Al2O3 Catalyst in the Combined Steam and Dry Reforming of Methane

Several mesoporous nickel-based catalysts with MgO-Al2O3 as the catalyst support were prepared using a co-precipitation method at a constant pH. The supports were prepared from the decomposition of an Mg-Al hydrotalcite-like structure which had already been prepared with Mg/Al=1. Prior to impregnating 10 wt.% nickel on the supports, the precursor was decomposed at several temperatures of 500, 600, 700, and 800 °C in order to elucidate the effect of calcination temperature on the physical and chemical characteristics of Mg-Al mixed oxides and the ultimate catalytic performance of the synthesized catalysts in the combined steam and dry reforming (CSDRM). The catalyst the precursor of which was calcined at 700 °C shows an excellent nickel dispersion and the highest activity among the other samples. It also exhibits the most stable performance during the long-term 36-hour run with high resistance against coke formation in the harsh condition of CSDRM.

Removal of perfluorooctanoic acid from water using calcined hydrotalcite – A mechanistic study

Calcined hydrotalcite (CHT) was evaluated for its potential removal of perfluorooctanoic acid (PFOA) from water in this study. The uptake of PFOA by CHT could be as high as 1587 mg/g (ca. 3.8 mmol/g), slightly larger than the anion exchange capacity (AEC) of the hydrotalcite (HT). Such a high removal was fast and pH independent, suggesting the versatile use of CHT. Due to the structural memory effect of HT, the removal involved adsorption of PFOA during HT recovery and intercalation of PFOA into the interlayer of restructured HT at low and high initial concentrations, respectively. Limited by the specific surface area and AEC, the intercalated PFOA would form a vertical bilayer or admicelle conformation. As such, the HT intercalated with PFOA became one-layer stacking with a basal spacing of 2.04 nm in contrast to the 3R polytype of recovered HT having a layer thickness of 0.78 nm, as confirmed by X-ray diffraction, thermogravimetric, and infra-red analyses. Due to its high PFOA removal capacity and large partitioning coefficient, the amount of CHT used, thus, the disposal of PFOA-laden solid could be minimized.

Oxidative Dehydrogenation of Ethanol over Vanadium- and Molybdenum-modified Mg-Al Mixed Oxide Derived from Hydrotalcite

Hydrotalcite or Mg-Al LDHs were synthesized by co-precipitation method. The Mg-Al mixed oxide was then derived by calcination of hydrotalcite at 450°C. The metal modified catalysts (Mo/Mg-Al and V/Mg-Al) were prepared by incipient wetness impregnation method. The obtained catalysts were characterized by several useful techniques and tested the reactivity for dehydrogenation and oxidative dehydrogenation of ethanol (gas-phase) to produce acetaldehyde. The catalytic reactions were performed at temperature range from 200 to 400°C for both non-oxidative and oxidative atmospheres. The results showed that the vanadium-modified hydrotalcite (V/Mg-Al) exhibited the highest ethanol conversion (34.3%) and acetaldehyde yield (15.5%) at 400℃ in the non-oxidative atmosphere. For the oxidative dehydrogenation of ethanol, the V/Mg-Al catalyst showed the highest activity at 400°C giving the ethanol conversion and acetaldehyde yield of 73.7% and 29.5%, respectively. This result probably related to the highest base density of V/Mg-Al catalyst (6.13 µmol CO2/m2) measured by CO2-TPD. The catalytic activity of Mg-Al catalyst and metal modified catalyst slightly decreased upon time-on-stream test for 10 h on oxidative dehydrogenation of ethanol due to carbon deposition.

In-Situ Deposition of Plasmonic Gold Nanotriangles and Nanoprisms onto Layered Hydroxides for Full-Range Photocatalytic Response towards the Selective Reduction of p-Nitrophenol

In this work, we present photocatalysis as a greener alternative to conventional catalysis where harsh reaction conditions, temperature and/or pressure are needed. Photodegradation of organic pollutants is a cost-effective, eco-friendly solution for the decontamination of water and air, and is a field that has been continuously growing over the last decade. Plasmonic metal nanoparticles absorb light irradiation that is transferred to the chemical reaction in a different fashion. Furthermore, plasmonic nanostructures can be combined with other materials, such as semiconductors or a basic support, to create hybrid systems capable of overcoming certain challenges that photocatalysis is facing nowadays and to expand the photocatalytic response towards the whole visible-near infrared (Vis-NIR) ranges. The main objective of this work has been to in-situ synthesize plasmonic anisotropic gold nanoparticles onto hydrotalcite (HT) and calcined hydrotalcite (CHT) supports by way of a sequential deposition-reduction (DR) process and to evaluate their efficiency as heterogeneous catalysts towards the selective oxidation of p-nitrophenol (hereafter 4-NP), a well-known model contaminant, either in the absence or the presence of full-range light irradiation sources (LEDs) spanning the whole UV-Vis-NIR range. Special attention has been paid to the optimization of the catalyst preparation parameters, including the pH and the concentration of reducing and stabilizing agents. Interestingly, the use of thermally modified hydrotalcites has enabled a strong metal-support interaction to induce the preferential formation of triangular-shaped Au nanoparticles with ca. 0.8 wt.% loading while increasing the colloidal stability and surface area of the catalyst with respect to the commercial untreated HT supports.

Correction to: Heterogeneous cycloaddition of styrene oxide with carbon dioxide for synthesis of styrene carbonate using reusable lanthanum–zirconium mixed oxide as catalyst

Development of environmentally benign green processes for utilization of carbon dioxide to synthesize value-added compounds using heterogeneous catalysis is desirable. One such proposed process is the cycloaddition of styrene oxide with carbon dioxide to synthesize styrene carbonate, synthesis of which has been well studied using various homogenous catalysts. The aim of the current work was to develop an active, selective and reusable heterogeneous catalyst for the cycloaddition of carbon dioxide to styrene oxide. Various solid catalysts such as 0.1% Li/MgO, calcined hydrotalcite (CHT), La–Zr mixed oxide (1:3 La/Zr), 0.1% La/MgO and ZrO2 were employed for cycloaddition of carbon dioxide to styrene oxide. Carboxylation of styrene oxide with carbon dioxide is enhanced by catalysts having both strong basic sites and weak acidic sites. Lanthanum–zirconia mixed oxide was prepared by combustion method using different compositions and evaluated for this reaction. La/Zr ratio of 1:3 was found to be the best among all studied and gave 90% conversion of styrene oxide with 100% selectivity of styrene carbonate at moderate temperature and pressure conditions in 3 h. The catalyst was characterized by various techniques to understand its textural properties. The catalyst was reused over three cycles without any loss of activity. The optimum reaction conditions were obtained by studying all process parameters in a laboratory batch stirred tank reactor (speed of agitation-1000 rpm, catalyst loading-2 × 10−2 g/cm3, 0.01 mol styrene oxide, DMF as solvent (total volume 30 mL), CO2 pressure-2.5 MPa, 130 °C). A detailed mathematical model was developed using Langmuir–Hinshelwood-Hougen–Watson mechanism in the absence of any transport resistances. The activation energy was calculated as 19.1 kcal/mol. The process is green and clean.

Optimization of the Transesterification of Waste Cooking Oil with Mg-Al Hydrotalcite Using Response Surface Methodology

Nowadays, biodiesel has become a very promising alternative to fossil diesel fuel, regarding environmental concerns and fuel resource depletion. Biodiesel is usually produced through homogeneous or heterogeneous transesterification of different fatty raw materials. Although main research has been carried out with homogenous catalysts, heterogeneous catalysts may be of interest due to ease of recovery and recycling, as well as readiness for continuous processing. In this work, calcined Mg-Al hydrotalcite (HT) was used for the heterogeneous transesterification of waste cooking oil. Three reaction parameters, namely, reaction time, amount of catalyst, and methanol-to-oil molar ratio, were optimized by means of Response Surface Methodology (RSM) at constant temperature (65 °C), using a Box-Behnken design. Optimal fatty acid methyl ester (FAME) content (86.23% w/w FAME/sample) was predicted by the model with an R-squared value of 98.45%, using 3.39 g of HT (8.5% w/w oil) and an 8:1 methanol-oil molar ratio, for a duration of 3.12 h. It was observed that calcination of HT, while avoiding the previous washing step, allowed the presence of chemical species that enhanced the effect of the catalyst. It can be concluded from this field trial that calcined and nonwashed Mg-Al hydrotalcite may be considered an effective basic catalyst for the production of biodiesel from waste cooking oil. Also, RSM proved to be a useful tool for predicting biodiesel yield.

Potential use of modified hydrotalcites as adsorbent of Bentazon and Metazachlor

The objective of the present research was to investigate the adsorption of pesticides on hydrotalcites modified with tetradecanedioate anions (TDD) or with humic acids (HA). In this study has been compared the pesticide adsorption on two different organohydrotalcites (OHTs) with tetradecanedioate anions in the interlayer (MA-TDD, MAF-TDD) and on other with humic acid (MAF-HA), all obtained by the coprecipitation method. Additionally, a calcined hydrotalcite has been used to adsorb Bentazon. X-ray diffraction of adsorption products on the organohydrotalcites MA-TDD and MAF-TDD showed the introduction of TDD anion and Metazachlor in the interlayer. Kinetic tests showed that the adsorption of pesticides Bentazon and Metazachlor involves intraparticle diffusion. Based on the results of regeneration tests, calcined hydrotalcite is an effective adsorbent for the removal of Bentazon from contaminated water. The results of regeneration tests suggest the possibility of using organohydrotalcites MA-TDD, MAF-TDD and MAF-HA to remove Metazachlor from contaminated water.