Organic dye removal from aqueous solutions by hierarchical calcined Ni-Fe layered double hydroxide: Isotherm, kinetic and mechanism studies

Synergistic effects of clays and cyanobacteria on the accumulation dynamics of soil organic carbon in artificial biocrusts

Biocrusts are the primary organic carbon reservoirs in desert areas, in which inorganic clays potentially playing significant roles; however, the specific details of these roles remain largely unclear. In this study, typical 1:1 type (kaolin) and 2:1 type (montmorillonite, MMT) clay minerals were added to artificial biocrusts to investigate their effect on the acquisition performance of soil organic carbon (SOC). After 84 days of cultivation, the enhancement effects of kaolin and MMT were significant, resulting in SOC increments that were 5.03 times and 4.08 times higher than those of the Algae group (without clay). Notably, the two types of clay exhibited different advantages in SOC accumulation. Due to its larger external specific surface area and higher cation exchange capacity, MMT contributes more effectively to SOC stability. Specifically, the mineralization quotient (qM), hot-water extractable organic carbon (HWEOC), and molecular structural stability of SOC in the MMT group were 0.3, 0.34, and 1.31 times those of the Algae group, respectively. In contrast, kaolin was more favorable for microbial growth and SOC formation due to its higher dissolved organic carbon (DOC) content. Microbial biomass carbon (MBC), chlorophyll-a (Chl-a), photosynthetic performance index (PIABS), and Shannon index in the kaolin group were 5.67, 2.44, 11.95, and 1.82 times those of the Algae group, respectively. These findings highlighted the synergistic effect for SOC accumulation of clay and cyanobacteria in artificial biocrust systems, clarified the specific roles of two typical clay minerals, and offered new insights for accelerating the restoration of nutrient-limited areas such as deserts.

Highly efficient and rapid removal of Congo red dye from textile wastewater using facile synthesized Mg/Ni/Al layered double hydroxide

Layered double hydroxides (LDH) are compounds with unique structures of hydroxide functional groups on their surfaces, and they have the proper arrangement of divalent and trivalent cations to adjust their unique catalytic actions. LDH was synthesized utilizing the co-precipitation technique and was thermally treated at 300 °C. The prepared compounds were chemically and structurally elucidated using FT-IR, XRD, SEM, BET, TG-DTA, and XPS characterization. We found that the thermal treatment of the prepared magnesium/nickel-LDH resulted in dehydration and dehydroxylation in its chemical structure. The crystallinity, the surface area, and the pore volume of the formed meso- and micropores were improved considerably after the thermal treatment. The efficiency of the uptake process was increased from 84 to 97% after the thermal treatment process, and the adsorption process tracked the Freundlich adsorption isotherm and pseudo-second-order kinetic model. The kinetics indicated the occurrence of three stages, and the diffusion of dye molecules into the pores was the rate-determining step. Different real water sample treatments showed the applicability of the thermally treated Mg/Ni/Al-LDH in the treatment process under optimized conditions. The presented mechanism of the uptake process using the prepared compounds comprises several interactions between the dye molecules and the thermally treated Mg/Ni/Al-LDH. The study presented the new application for Mg/Ni/Al-LDH in the as-prepared and thermally treated forms to uptake Congo-red (CR) dye from textile effluents.

High-performance cellulose acetate fibers-loaded Alca layered double oxide adsorbents towards efficient elimination of anionic pollutants: Mechanism adsorption and RSM-CCD approach

In the present research, we investigate Congo red (CR) removal by layered double hydroxide and oxide AlCa on cellulose acetate (CA) fiber as anion-adsorbents in aqueous solution. The as-prepared composite was characterized by FE-SEM, XRD, FTIR, EDS-mapping and BET-BJH analyses. The CR adsorption ability on AlCa LDH/CA and AlCa LDO/CA adsorbents was evaluated. The removal property, dye adsorption and filtration properties of the AlCa LDO/CA composite were studied for removal CR based on central composite design (CCD) technique through investigating operational variables (temperature, adsorbent dosage, pH and contact time). The fabricated AlCa LDO/CA composite indicates a high removal efficiency up to 98.7 % for the CR removal in the 16 min. The data of the adsorption equilibrium were described by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms, and exhibited that AlCa LDH/CA fibers and AlCa LDO/CA fibers followed a pseudo-second-order kinetic model and Langmuir isotherm. The stability of Al-Ca-LDO/CA fibers nanocomposite was indicated that it was >95 % after eight cycles for removal of CR in the batch method on stirrer. The findings illustrated that appropriate AlCa LDO/CA fiber could be an efficient technique for CR elimination.

3D magnetic flower-spherical Fe2O3-NiO derived from NiFe-layered double hydroxides for the efficient removal of Bensulfuron methyl: Morphological control and bimetallic synergy

Three-dimensional (3D) magnetic flower-spherical Fe2O3-NiO derived from NiFe-layered double hydroxides (NiFe-LDHs) was fabricated through urea hydrothermal and calcination methods. The as-prepared materials were applied to activate PMS to degrade one of herbicide named Bensulfuron methyl (BSM). Fe2O3-NiO-1 demonstrated the highest catalytic activity and the lowest ions leaching by comparing the performance of LDHs and derivative bimetallic oxide synthesized by co-precipitation method, urea hydrothermal method and direct calcination method. Based on the results of SEM, BET and CV, the high catalytic activity of Fe2O3-NiO-1 originated from 3D morphology, lager specific area and pore size and faster electron transfer capability. The factors influencing the degradation performance were investigated and 0.1 g·L-1 Fe2O3-NiO could effectively activate PMS (1 mmol·L-1) to completely remove 10 mg·L-1 BSM within 30 min at pH 7.0. In Fe2O3-NiO/PMS system, OH, SO4- and 1O2 were produced and contributed to the BSM removal according to the results of EPR and quenching experiments. In order to expand its application range, Fe2O3-NiO/PMS system was used to degrade aniline (AN), sulfamethoxazole (SMZ), phenacetin (PNT), bisphenol A (BPA) and 2,4,6-triclofen (2,4,6-TCP) and the results showed the degradation efficiency could reach 90 % or more. Additionally, the application of catalysts in different actual water samples and the ability of reuse were tested. Based on the strategies of bimetallic synergy and morphology control, Fe-based bimetallic oxides with 3D morphology were developed in this study, which could effectively enhance the catalytic activity and inhibit the dissolution of metal ions, providing the design ideas for the construction of efficient catalysts and the removal of complex organic pollutants.

Fabrication of rare-earth cerium-doped nickel-copper ferrite as a promising photo-catalyst for congo red-containing wastewater treatment

Synthetic organic dyes are becoming the major class of water pollutants leading to malignant detriments to the ecology. Consequently, this research focuses on remediating this circumstance utilizing a novel catalytic material, namely, cerium-doped spinel ferrite Ni0.6Cu0.4Ce x Fe2-x O4 (x = 0.0, 0.5, 1.0, 1.5), developed using the chemical coprecipitation technique and characterized using FTIR, XRD, FE-SEM, EDX and VSM analysis. The particles have shown band gap values ranging from 4.29 to 2.01 eV. The as-synthesized nano-sized particles were employed as a photocatalyst to degrade the complex structure of congo red (CR) dye. About 91% of the dye was degraded with 60 mg of the catalyst under visible light irradiation with the highest cerium-doping (x = 1.5) at a pH below 6.8, which was the zero-surface charge pH for the particle. Batch studies were performed to optimize all the conditions, including the dose, concentration, pH, and different light energy sources. Recyclability of the catalyst was also investigated, which was supported by the higher stability of the recovered particles through XRD analysis. Reaction kinetics for this system were evaluated along with three isotherm models. Moreover, the scavenging test indicated that the major active species leading to this degradation was hole (h+), and a schematic degradation mechanism is presented. Following that, this model can successfully be used for wastewater treatment.

Effective enrichment and separation of three flavonoids from Ohwia caudata (Thunberg) H. Ohashi using magnetic layered double hydroxide/ZIF-8 composites and pCEC

In this study, Fe3O4@ZnCr-layered double hydroxide/zeolitic imidazolate frameworks-8 (MLDH/ZIF-8) magnetically functionalized composites were synthesized by co-precipitation and in situ growth based on the advantages of LDHs and ZIF-8 using Fe3O4 nanoparticles as a magnetic substrate to obtain adsorbents with excellent performance. Moreover, the composite was used for the efficient enrichment of flavonoids in Chinese herbal medicines. The internal structures and surface properties were characterized by SEM, Fourier transform infrared spectroscopy, X-ray diffraction and so on. MLDH/ZIF-8 exhibited a large specific surface area and good paramagnetic properties. The MLDH/ZIF-8 magnetic composite was used as a magnetic solid-phase extraction (MSPE) adsorbent, and a MLDH/ZIF-8 MSPE-pressurized capillary electrochromatography coupling method was developed for the separation and detection of flavonoids (luteolin, kaempferol and apigenin) in a sample of the Chinese herb Ohwia caudata (Thunberg) H. Ohashi. The relevant parameters affecting the extraction efficiency were optimized to determine the ideal conditions for MSPE. 5 mg of adsorbent in sample solution at pH 6, vortex extraction for 5 min, elution with 1.5 mL of ethyl acetate for 15 min. The method showed good linearity in the concentration range of 3-50 μg mL-1 with correlation coefficients of 0.9934-0.9981, and displayed a relatively LODs of 0.07-0.09 μg mL-1. The spiked recoveries of all analytes ranged from 84.5% to 122.0% with RSDs (n=3) between 4.5% and 7.7%. This method is straightforward and efficient, with promising potential in the separation and analysis of active ingredients in various Chinese herbal medicines.

Hierarchical Mg/Al hydrotalcite oxide hollow microspheres with excellent adsorption capability towards Congo red

A novel citrate anion-intercalated Mg/Al layered double hydroxide (CA-LDH) is synthesized via a one-step hydrothermal process. The synthesized CA-LDH is a hollow flower-like microsphere composed of thin nanoflakes (10 nm in thickness). After calcination, the formed Mg/Al layered double oxide (CA-LDO) hollow microspheres possess a high specific surface area of 247.8 m2 g-1 and a high pore volume of 0.97 cm3 g-1, which endow them with excellent adsorption ability towards Congo red (CR). The maximum adsorption capacity of CR onto CA-LDO can reach up to 1883 mg g-1. The significantly improved adsorption capacity of CA-LDO can be attributed to its unique structures of hierarchical hollow microspheres, in which the hierarchical porous shell layer provides enough adsorption sites to anchor the dye molecules, and the hollow core can preserve the absorbed dye. This study provides a promising novel adsorbent which can be used for efficient water remediation.

Magnetic Rubber@ magnesium aluminum layered double hydroxide as nanostructured sorbent; application in determination of estrogenic hormones and bisphenol A

A magnetic solid-phase extraction (MSPE) method was developed for the enrichment of trace amounts of estrone (E1), 17-β-estradiol (E2) and bisphenol A (BPA) from aqueous samples using the Rubber-Fe3O4@SiO2@Mg-Al Layered double hydroxide followed by determination by HPLC. The proposed sorbent was characterized by X-ray diffraction, Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Vibrating-sample magnetometer, Thermal gravimetric analysis, N2 adsorption/desorption Brunauer-Emmett-Teller surface analysis, Barrett-Joyner-Halenda pore size analysis and Energy dispersive X-ray spectroscopy. Factors affecting the extraction efficiency such as pH, ionic strength, extraction temperature and time, desorption solvent and time were optimized. The limit of detection and quantification were obtained as 0.33, 1 µg L-1 for the E1 and E2 and BPA, respectively. Also, linear range of the method were 1-150, 1-100 and 1-150 µg L-1for E1, E2, and BPA, respectively. Relative standard deviations (RSD%) for the repeatability of extraction on one sorbent were obtained as 2.98, 1.31 and 3.50%, also, sorbent to sorbent repeatability were investigated and RSD% values were obtained as 7.58, 8.35 and 8.12% for E1, E2 and BPA, respectively.

Sulfur vacancy regulation and multipolarization of NixCo1S nanowires-decorated biotemplated structures to promote microwave absorption

It is a novel and practical method to use natural porous biomaterials as microwave absorber. In this study, Ni_xCo₁S nanowires (NWs)@diatomite (De) composites with one-dimensional (1D)-NWs and three-dimensional(3D)-De composites were prepared by a two-step hydrothermal method using De as template. The effective absorption bandwidth (EAB) of the composite reaches 6.16 GHz at 1.6 mm and 7.04 GHz at 4.1 mm, covering the entire Ku band, and the minimum reflection loss (RLmin) is less than -30 dB. The excellent absorption performance is mainly due to the bulk charge modulation provided by the 1D NWs and the extended microwave transmission path within the absorber, coupled with the high dielectric loss and magnetic loss of the metal-NWS after vulcanization. We present a high-value method that combines vulcanized 1D materials with abundant De to achieve the lightweight broadband efficient microwave absorption at the first time.

Starch modified NiFe layered double hydroxide composites for better adsorption and photocatalytic removal of reactive dye and piroxicam-20 drug

One of the most omnipresent problems to the environment is the efficient removal of textile dyes and non-steroidal drugs from wastewater. For this purpose, renewable, sustainable, and biodegradable biopolymers are used. In this study, starch (S) modified NiFe-layered double hydroxide (LDH) composites were successfully synthesized by the co-precipitation method and have been examined as a catalyst for the effective adsorption of reactive blue 19 dye, reactive orange 16 dye, and piroxicam-20 NSAID from wastewater and photocatalytic degradation of reactive red 120 dye. The physicochemical properties of the prepared catalyst were assessed by XRD, FTIR, HRTEM, FE-SEM, DLS, ZETA, and BET. The coarser and more porous micrographs are shown in FESEM, indicating the homogeneous dispersion of layered double hydroxide on starch polymer chains. The S/NiFe-LDH composites have a slightly greater S_BET (6.736 m²/g) than NiFe LDH (4.78 m²/g). The S/NiFe-LDH composite shows remarkable ability in the removal of reactive dyes. The band gap value of NiFe LDH, S/NiFe LDH (0.5:1), and S/NiFe LDH (1:1) composites was calculated as 2.28 eV, 1.80 eV, and 1.74 eV, respectively. The q_max assessed from Langmuir isotherm for removal of piroxicam-20 drug, reactive blue 19 dye, and reactive orange 16 was 2840 mg/g, 149.47 mg/g, and 182.4 mg/g, respectively. The activated chemical adsorption without product desorption is predicted by the Elovich kinetic model. With reactive red 120 dye, S/NiFe-LDH shows photocatalytic degradation within 3 h of irradiation of visible light with 90% removal efficiency and follows a pseudo-first-order kinetic model. The scavenging experiment confirms the involvement of electrons and holes in photocatalytic degradation. With a little decline in adsorption capacity up to five cycles, starch/NiFe LDH was easily regenerated. So, the suitable adsorbent required for wastewater treatment is nanocomposites of LDHs and starch as they enhance the chemical and physical attributes of the composite structure with greater absorption capabilities.

Adsorption performance of tetracycline on NiFe layered double hydroxide hollow microspheres synthesized with silica as the template

Tetracycline (TC) has poor degradability and hepatotoxicity which will increase the burden on the aquatic environment when discharged into lakes in large quantities. LDH materials are often used as adsorbents because of their superior surface area and controllability of morphology. Herein, NiFe LDH hollow microspheres (NFHMS) were synthesized by a facile hydrothermal method. The removal of tetracycline by the as-prepared material in an aquatic environment was systematically investigated through comprehensive characterizations. The NFHMS sample presents a larger specific surface area than the two control samples, which contributes to its higher adsorption performance. The adsorption mechanisms of TC on NFHMS is mainly electrostatic adsorption. The fitting results of experimental data coincide well with pseudo-second-order and Weber-Morris models through kinetic simulation. Moreover, the Langmuir model is verified to be more suitable than the Freundlich model in elucidating molecular surface adsorption, and the maximum adsorption capacity of NFHMS obtained from the Langmuir model is 90.9 mg g^-1. Higher temperature is beneficial to improve the adsorption performance, and the adsorption process is spontaneous and endothermic. The initial pH of the solution will affect the adsorption capacity, and the partial neutral condition is more favorable. In addition, NFHMS sample exhibits good stability in cyclic tests. Therefore, NFHMS material is expected to be a very promising adsorbent for treating tetracycline in wastewater.

Enhanced removal of Eriochrome Black T from water using biochar/layered double hydroxide/chitosan hybrid composite: Performance evaluation and optimization using BBD-RSM approach

In this research work, a novel hybrid composite consisting of biochar (B), layered double hydroxide (CuFe) and chitosan (CS) (B-CuFe-CS) was produced using an ultrasonication-assisted co-precipitation method. The resultant composite was employed for adsorptive removal of Eriochrome black T (EBT) from water. Physicochemical characterization indicated that the B-CuFe-CS containing 10 wt % CS exhibited a heterogeneous structure with better crystallographic and textural characteristics. The B-CuFe-CS with abundant surface functionalities (-CO, -C-O, -OH, -NO_3, and MMO), facilitates faster and enhanced removal of the EBT. The kinetic results showed better fitting to the pseudo-second order model, and equilibrium was achieved within 30 min. Equilibrium data was well explained by Langmuir and Redlich Peterson isotherm models (R² > 0.98), indicating the EBT removal onto B-CuFe-CS followed monolayer adsorption. The maximum adsorption capacity was 806.4 mg/g, which was higher than pristine B-CuFe (476.19 mg/g) and many other adsorbents. The spectroscopic analysis (FTIR and XPS) and experimental results suggested that EBT adsorption is mainly governed by electrostatic, chemical and anion-exchange interactions. It is evident from these results that coupling B-CuFe composite with bio-filler (chitosan) resulted in an efficient bio-adsorbent to effectively purify dye-contaminated water streams.

Nanostructured Materials for Water Purification: Adsorption of Heavy Metal Ions and Organic Dyes

Chemical water pollution poses a threat to human beings and ecological systems. The purification of water to remove toxic organic and inorganic pollutants is essential for a safe society and a clean environment. Adsorption-based water treatment is considered one of the most effective and economic technologies designed to remove toxic substances. In this article, we review the recent progress in the field of nanostructured materials used for water purification, particularly those used for the adsorption of heavy metal ions and organic dyes. This review includes a range of nanostructured materials such as metal-based nanoparticles, polymer-based nanomaterials, carbon nanomaterials, bio-mass materials, and other types of nanostructured materials. Finally, the current challenges in the fields of adsorption of toxic materials using nanostructured materials are briefly discussed.

Layered Double Hydroxide-Assisted Fabrication of Prussian Blue Membranes for Precise Molecular Sieving

Prussian Blue (PB), which was first discovered as robust blue-colored pigment in the year 1706, has shown promising prospects in disease treatment, energy conversion, water splitting, and sensing. Relying on the uniform 3.2 Å-sized pore channels as well as high stability in aqueous environments, in this study, we pioneered in situ preparation of polycrystalline PB membranes to justify their dye rejection and metal ion discrimination ability in aqueous environments. Among various factors, the introduction of calcined NiFe layered double hydroxide buffer layers on porous α-Al₂ O₃ substrates was found to play a paramount role in the formation of continuous polycrystalline PB membranes, thereby leading to excellent dye rejection efficiency (>99.0 %). Moreover, prepared PB membranes enabled discriminating different monovalent metal ions (e.g., Li⁺ , Na⁺ , and K⁺ ) depending on their discrepancy in Stokes diameters, showing great promise for lithium extraction from smaller-sized metal ions.

Surface engineering of silica based materials with Ni-Fe layered double hydroxide for the efficient removal of methyl orange: Isotherms, kinetics, mechanism and high selectivity studies

Herein, low-cost diatomite (DE) and bentonite (BE) materials were surface modified with Ni-Fe layered double hydroxide (LDHs) (represented as NFD and NFB respectively), using a simple co-precipitation procedure for the removal of methyl orange (MO) dye from water. The adsorbents of both before and after MO adsorption have been studied by XRD, N₂ adsorption-desorption isotherm, FTIR, FESEM-EDX and XPS characterization. The zeta potential analysis was used to observe the surface charge of adsorbents within the pH ranges of 4-10. The MO removal efficiency was significantly improved after LDHs modification, showing a 94.7% and 92.6% efficiency for NFD and NFB at pH 6, respectively. Whereas bare DE and BE have shown removal efficiency of 15.5% and 4.9% respectively. The maximum adsorption capacities of NFD and NFB using the Langmuir isotherm model were found to be 246.9 mgg^-1 and 215.9 mgg^-1 respectively. The designed NFD showed high selectivity towards anionic-based dyes from water and also the effect of salts shows the dye removal percentage was increased and decreased for the addition of Na₂SO₄ and NaCl, respectively. The reusability of NFD and NFB have been studied for a maximum of five cycles and they can remove MO up to four cycles. Therefore, the designed adsorbents can be very effective towards the removal of MO from water and they may be useful for dye-based wastewater treatment.

Co-precipitation based on layered double hydroxides and anionic surfactants for preconcentration of six benzoylurea insecticides in soft drinks before simultaneous analysis by high-performance liquid chromatography

Layered-double hydroxides (LDHs) modified with anionic surfactants via a co-precipitation method were developed for preconcentrating and simultaneous analysis of six benzoylurea insecticides (BUs) by high-performance liquid chromatography (HPLC). The anionic surfactants with different chain lengths, including sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium 1-nonane sulfonate (SNS), and sodium 1-hexane sulfonate monohydrate (SHS) were investigated to improve the extraction efficiency of LDHs. The SDBS-LDHs provided the highest efficiency for the enrichment of the BUs studied. Under the chosen conditions, enrichment factors in the range of 38-69 and detection limits in the range of 0.1-0.3 μg L^-1 were achieved. Good reproducibilities (RSD < 13.8%) and recoveries (71.4-118.7%) were also obtained. The proposed preconcentration method, used as an in situ procedure offers rapid and simple simultaneous preparation of LDHs and extraction of BUs. The method was successfully applied for residue analysis of BUs in fruit- and flower-derived soft drink samples.

Removal of Isolan Dark Blue 2SGL-01 from aqueous solutions onto calcined and uncalcined (Mg-Zn)/(Al-Fe)-(CO3)/Cl layered double hydroxides

The adsorption process of the industrialized dye Isolan Dark Blue 2SGL-01 (IDB) onto (Mg-Zn)/(Al-Fe)-(CO3)/Cl layered double hydroxides (LDHs) coded LDH21 and LDH22 and its calcined products CLDHs (CLDH21 and CLDH22), respectively, was investigated. The characterization of LDHs and CLDHs before and after loading with IDB by Fourier transform infrared, scanning electron microscope and surface area measurements showed a typical hydrotalcite structure and confirmed the loading of IDB. The adsorption parameters; initial pH, shaking time, adsorbent dose, initial concentration of IDB dye and temperature were studied. The optimum conditions for IDB adsorption were pH 4.3 and shaking time 3 h. A complete removal of IDB (> 99%) was achieved using a dosage of 2.0 g L− 1 CLDHs or LDH22, and 3.0 g L− 1 of LDH21. The adsorption processes were suggested to be best described by the pseudo-second order kinetics and Langmuir-type adsorption isotherm with monolayer capacities of 75, 91, 427 and 530 mg g− 1, onto LDH21, LDH22, CLDH21 and CLDH22, respectively. The loaded IDB was recovered from LDHs and CLDHs adsorbent using Na2CO3. CLDH22 showed best adsorption capacity of 530 mg g− 1. Its adsorption thermodynamic parameters ∆Gadsorption, ∆Hadsorption and ∆Sadsorption indicated that the adsorption processes were spontaneous and endothermic in nature. CLDH22 was successfully applied for the removal of IDB from simulated dyeing process with removal efficiency 97%.

High selectivity and adsorption proficiency of surfactant-coated selenium nanoparticles for dye removal application

The rate of environmental pollution augmenting at an alarming rate due to the continuous disposal of toxic dyes directly into the environment and water streams. The direct contact of dyes with water resources directly affects the living beings. The identification of superior methods for the treatment of water pollution caused due to effluent dyes needs higher consideration among researchers for the well-being of living flora and fauna. The available methods for controlling the decontamination of water through toxic dyes have various drawbacks. So, it is highly significant to develop such materials which can easily adsorb the dyes without causing any toxic effect on the environment and living beings. While keeping all the facts in mind, the current work highlights the comparative enhancement in adsorption capacity and selectivity of Brij-58-coated selenium nanoparticles (Brij-58@Se NPs) towards the removal of bromophenol blue (BB) dye from series of chosen dyes in aqueous media. The fabricated Se NPs were methodically characterized and the adsorption behaviour displayed fast adsorption efficiency (98% within 6 min) for BB dye out of series of chosen dyes. The optimization studies were carried out to verify the influence of working variables such as pH (2.0-12.0), response time (1-10 min), dosage amount (0.1-80 mg/l) and concentration of BB dye (1-70 ppm). The adsorption process found to be best fitted for Freundlich adsorption isotherm and pseudo first-order kinetic model. The interference studies of different cationic, anionic species including dyes or metal ions suggested the higher efficiency of Brij-58@Se NPs for adsorptive removal of BB dye from aqueous media. The efficacy of the adsorbent was further tested in six different water resources and displayed 95% adsorption efficiency for BB dye in different wastewater samples. Therefore, Brij-58@Se NP is expected as a potential adsorbent for the adsorption of organic dyes from wastewater samples.

Review on nickel-based adsorption materials for Congo red

Excessive synthetic dyestuffs in the aquatic environment pose various ecological and health issues that are detrimental to sustainable development. Adsorption is considered a feasible technique of eliminating dye pollutants from the water environment because of its advantages of high efficiency, low cost, easy operation, and absence of secondary pollution. Among the many dyes, Congo red (CR) is a widely used azo dye. Nickel-based materials, including nickel hydroxide, nickel oxide, nickel-containing layered double hydroxides, nickel-based spinel and metal-organic frameworks, metallic nickel, nickel-based sulfide, and nickel composites, have been extensively studied for CR adsorption due to their morphological diversity, large specific surface area, and strong affinity toward CR. However, fabricating nickel-based adsorbents with high efficiency and stability and excellent recyclability for practical application remains a challenge. This review outlines the research progress of nickel-based materials in CR adsorption. The interaction between CR molecules and nickel-based adsorbents is systematically presented, and the possible adsorption mechanisms are summarized. Finally, the challenges and future development directions of the practical application of nickel-based adsorbent materials are proposed.

Catalytic hydrothermal liquefaction of Gracilaria corticata macroalgae: Effects of process parameter on bio-oil up-gradation

Hydrothermal liquefaction (HTL) of Gracilaria corticata (GC) macroalgae was studied over a series of nickel-iron-layered double oxides (NiFe-LDO) supported on activated bio-char catalysts at 280 °C and different solvents medium. Maximum bio-oil yield (56.2 wt%) was found with 5%Ga/NiFe-LDO/AC catalyst at 280 °C under ethanol solvent. The catalytic HTL up-gradation decreased the bio-char yield significantly. However the bio-oil quality significantly improved with using the 5%Ga/NiFe-LDO/AC catalyst. Also, improved performance with higher amount of bio-oil and lower amounts of bio-char and gas were achieved, which is due the several reactions happening during the HTL process. Catalytic HTL also revealed that introducing NiFe-LDO nanosheets into the activated char could result in NiFe-LDO/AC catalysts of higher surface area and increased active sites. Being impregnated by 5%Ga, catalysts with improved acid sites and thereby, advanced deoxygenation and aromatization activities were achieved. Hence Ga/NiFe-LDO/AC could be considered as a promising catalyst HTL bio-oil upgrading.

Adsorption of Orange II Onto Zn2Al-Layered Double Hydroxide Prepared From Zinc Ash

The dye industry is one of the largest water consuming industries, and at the same time generates large quantities of wastewaters. The resulting wastewaters require proper treatment before discharge, because the dye contents have a negative effect on the water body and organisms present in it. The most efficient treatment method for water containing dyes is represented by adsorption processes. The challenge with these adsorption processes is to develop new, efficient, viable, and economic adsorbent materials. Therefore, in the present paper, the performance of Zn₂Al-layered double hydroxide, prepared from an industrial waste (zinc ash) as a zinc source, was investigated in the Orange II dye adsorption process. The Zn₂Al-layered double hydroxide prepared from secondary sources presents similar morphological and structural characteristics as those prepared from analytical grade reagents. The influence of initial dye concentration, adsorption time, solid:liquid ratio, pH, and temperature was evaluated in order to confirm the benefit of this waste valorization. A comparison with the reference Zn₂Al-layered double hydroxide prepared from analytical grade reagents was performed and the results show that due to the small presence of impurities, the material prepared from zinc ash shows better adsorption capacities (q_max,exp = 42.5 mg/g at 293 K) than the material prepared from reagents (q_max,exp = 36.9 mg/g at 293 K), justifying the utilization of secondary sources for layered double hydroxides preparation. The proposed treatment process presents advantages from both economic and environmental protection point of view.

Dissolvable Mg/Al layered double hydroxides and surfactant as an extractant for trace analysis of benzoylurea insecticides by high performance liquid chromatography

A rapid and simple preconcentration method using dissolvable Mg/Al layered-double hydroxides (LDHs) and high performance liquid chromatography-photodiode array detection (HPLC-PDA) was developed for the analysis of benzoylurea insecticides (BUs) in water and honey samples. The proposed dissolvable LDHs for the extraction can be prepared in one step by the sequential addition of sodium hydroxide, magnesium chloride, aluminium chloride, and sodium dodecyl sulfate into the sample solution containing the target BUs. The co-precipitate phase was simply obtained after centrifugation, and the phase was then dissolved with formic acid before analysis by HPLC. The developed method provided an enrichment factor of 12.5-23.7. LODs were obtained in the range of 0.1-0.3 μg L^-1 for deionized water, 0.2-2.0 μg L^-1 for environmental waters, and 0.5-2.0 μg L^-1 for the analyzed honey samples. Good recoveries ranging from 78.4 to 117.8% and 72.7 to 117.9% for water and honey samples, respectively, were obtained.

Fabrication and Characterization of Novel ZnAl-Layered Double Hydroxide for the Superadsorption of Organic Contaminants from Wastewater

An imidazole ester skeleton (zeolitic imidazolate framework (ZIF)) was grown on the surface of a ZnAl-layered double hydroxide (ZnAl-LDH) material to form a porous composite (ZIF-ZnAl-LDH). To understand the adsorption characteristics of the two materials, the effects of pH, adsorption time, and adsorption concentration on the adsorption of Congo red (CR) solution were investigated comprehensively. In addition, ZnAl-LDH and ZIF-ZnAl-LDH were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The results clearly showed that ZnAl-LDH had a lamellar structure with a diameter of approximately 200-500 nm and ZIF-ZnAl-LDH had a regular three-dimensional hexagonal structure. The kinetics and thermodynamics of the CR adsorption by ZnAl-LDH and ZIF-ZnAl-LDH can be described using pseudo-second-order (PSO) and Langmuir models, respectively. The highest value of adsorption capacity obtained from the Langmuir equation was equal to 625.00 and 909.09 mg/g for these two compounds, respectively. The values of the standard Gibbs free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) obtained for these adsorption processes prove that the adsorption of CR by ZnAl-LDH and ZIF-ZnAl-LDH is a spontaneous endothermic process. Furthermore, through the analysis of the characterization results, it is concluded that the adsorption mechanisms of ZnAl-LDH and ZIF-ZnAl-LDH on CR are mainly dominated by electrostatic action, functional group action, surface pore adsorption, and anion exchange.

In-situ synthesis of calcium aluminum layered double hydroxides for advanced treatment of leachate biochemical tail water

In the leachate system, Ca-Al-LDH was synthesized in situ by adding calcium aluminum material (AC) and Ca (OH)₂. In the process of synthesis, the removal efficiencies of UV254, COD and TOC in the leachate reached 85.51%, 73.85% and 74.71%, respectively, and the organic matter could be effectively removed. XRD (X-Ray Diffraction) characterization analysis displayed that when AC and Ca (OH)₂ were added at a ratio of 3:1, Ca-Al-LDH could be synthesized efficiently. The effect of this method on the removal of pollutants in leachate was better than that of Ca-Al-LDH. EEM (Excitation Emission Matrix) and GC-MS (Gas Chromatography-Mass Spectrometer) characterization analysis showed that these results could be attributed to the coagulation of calcium aluminum material AC, LDH surface adsorption and ion exchange.