Initial Solution Concentration Research Articles

Preparation of agar functionalized graphene oxide-immobilized copper ferrite aerogel for dye degradation via dark-Fenton oxidative process

Dye and textile industries are one of the main causes of water pollution and put the environment and health of society at risk. Developing new materials to decontaminate industrial waste effluents containing dyes as pollutants is challenging due to numerous issues, including tailoring recyclable and biodegradable agents. This study focuses on applying an advanced oxidation process, electro-Fenton for the treatment of dye-containing wastewater using agar-functionalized graphene oxide-immobilized copper ferrite aerogel. The objective is therefore to determine the optimal conditions for the degradation of model pollutants methylene blue (MB). MB was oxidized and degraded through the dark-Fenton process using Agar@GO-CuFe2O4 as a new biobased catalyst. The effect of the operating parameters was then evaluated to determine the optimal conditions. The degradation process was screened for different initial concentrations of dye solution between 10 and 150 mg/l, a volume range of H2O2 between 0.5 and 2.5 ml, and different pH from 2 to 7. The results show that 99.89 % of the MB with the initial concentration of 150 ppm was degraded by 20 mg of the catalyst and 2 ml of H2O2 (30 % W/W) at 40 °C and pH = 6. Pseudo-second-order kinetics satisfactorily describes the experimental data. SynopsisThe prepared catalyst can be applied to oxidize industrial effluents before they are released into the environment.

Sorption of tartrazine dye from aqueous solution using activated carbon prepared from Cocos nucifera husk

Sorption of Tartrazine dye from aqueous solution using activated carbon prepared from Cocos nucifera (coconut) husk was investigated in this work. The coconut shell was first carbonized at 700°C in a muffle furnace and activated with NaOH for one hour. The activated carbon (AC) was applied to remove tartrazine from aqueous solutions over a concentration range of 50-250 mg/L respectively. Adsorbent features were determined using X-ray fluorescence (XRF), Fourier transformed infrared spectroscopy (FTIR), Scanning electron micrograph (SEM) techniques. Based on this investigation, adsorption of Tartrazine dye is strongly affected by initial solution pH, initial solution concentrations, dosage, and time of contact which favours the removal. Except for temperature which was found to decrease with increase temperature for AC, while adsorption capacity of Tartrazine was found to decrease with increase in adsorbent dosage for AC. The optimum pH for adsorption Tartrazine removal was found to be 3. The experimental data of Tartrazine was found to fit the linearized Langmuir isotherm better than the Freundlich isotherm and D-R model indicating a monolayer adsorption. On effect of initial solution concentration, adsorption capacity of Tartrazine was found to increase with increase in concentration for AC. Kinetic data fitted more into pseudo second order model than first order and intra particle diffusion model, suggesting that chemisorption dominate the rate limiting step. The calculated thermodynamic parameters – Gibbs free energy, enthalpy change and entropy change indicated that adsorption of Tartrazine was endothermic and not spontaneous meaning the chemisorption dominates physisorption.

Study on the ability to treat methylene blue in water and textile dyeing wastewater from sedge mats of the ZnAlCO<sub>3</sub> hydrotalcite modified by Cu<sup>2+</sup> ion under visible light

Hydrotalcite ZnAlCO3 and modified hydrotalcite CuZnAlCO3 were synthesized by a co-precipitation method from nitrate salts of Al, Zn and Cu as precursors. Using Na2CO3 salt to provide CO32- interlayer ion and NaOH 2N solution to adjust the pH of the reaction mixture to pH = 9.5. The obtained samples were characterized by physical analysis methods: XRD, EDX, SEM image, BET, UV-Vis DRS. The characterization results showed that the two synthesized samples H and 3CuH (molar ratio of Zn:Al and Cu:Zn:Al are 7:3 and 3:4:3 for H and 3CuH, respectively) had a lamellar structure similar to hydrotalcite with ions CO32- in the interlayer. The molar ratio of Zn:Al and Cu:Zn:Al in the samples is quite similar to the amount taken to synthesize the samples. The specific surface area increased from 16.1 to 33.9 m2/g, while the band gap energy Eg decreased from 3.02 to 1.25 eV, corresponding to H and 3CuH. The photocatalytic activity of the 3CuH sample in the decomposition reaction of methylene blue (MB) was much better than that of the sample H at the concentrations of MB investigated (10, 25, 50 ppm). The catalytic activity of the 3CuH material depended on the initial concentration of MB solution and the pH of the medium. Free radicals OH• and holes h+ play an important role in the photocatalytic activity of 3CuH material. In addition, the 3CuH sample is capable of effectively treating blue sedge textile dyeing wastewater with the decomposition efficiency of blue substances reaching over 94% after 4 hours of illumination, the mineralization efficiency of pigments reaching nearly 88% after 7 hours of lighting.

Porous metal-organic framework-acrylamide-chitosan composite aerogels: Preparation, characterization and adsorption mechanism of azo anionic dyes adsorbed from water

Micro- and nano-metal-organic frameworks with different adsorption properties were prepared by a time-modulation hydrothermal method. By comparing the adsorption properties, the most effective MIL-68(Fe)-12 was selected to be mixed with chitosan (CS), and porous metal-organic framework-acrylamide-chitosan composite aerogel (PMACA) was prepared by introducing acrylamide prior to glutaraldehyde crosslinking. The adsorption capacity of PMACA doped with acrylamide was as high as 2086.44 mg·g−1. The adsorption performance of PMACA was 1.48 times higher compared to the porous metal-organic framework-chitosan composite aerogel (PMCA) undoped with acrylamide. With the introduction of acrylamide, the stability of PMACA was improved, making it less prone to dispersion and decomposition. Structural characterization and adsorption properties were analyzed using methods such as XRD, FTIR, TGA, SEM, BET, and Zeta potential. The adsorption performance of PMACA was investigated further through batch tests with variables such as adsorbent dosage, pH, contact time, initial CR solution concentration, and temperature. The model fitting of PMACA was consistent with the pseudo-second-order model and the Sips model. The adsorption thermodynamics showed that high temperature promoted spontaneous adsorption behavior. PMACA showed a recovery rate of approximately 86 % after six cyclic adsorption tests. PMACA maintained a recovery rate of roughly 86 % after six cyclic adsorption tests. The combined effects of electrostatic attraction, hydrogen bonding, and π-π conjugation resulted in excellent adsorption performance, while pore filling also contributed to the efficient adsorption of Congo red (CR).

Fabrication of sodium alginate-doped carbon dot composite hydrogel and its application for La (III) adsorption and enhanced the removal of phosphorus.

Adsorption is an effective method for the removal of hazardous substances from wastewater. In this work, a low-cost and environmental-friendly composite hydrogel material of sodium alginate doped with nitrogen doped carbon dots (SA@NCDs) was fabricated by impregnation for lanthanide and enhanced phosphorus adsorption in wastewater. The effects of NCDs doping amount, dosage, pH, initial solution concentration, adsorption time and temperature on the process of La (III) adsorption by SA@NCDs were investigated. The adsorption isotherms fitted to Langmuir isotherm model (R2 = 0.9970-0.9989) and the adsorption kinetics followed pseudo-second-order kinetic model (R2 = 0.9992). The maximum adsorption capacity of the adsorbent for La (III) was 217.39mg/g according to the Langmuir model at 298.15K. After five cycles, the removal efficiency of La (III) adsorbed by SA@NCDs was still 85.1%. Moreover, the loaded La (III) enhanced the adsorption of phosphorus. The La (III)-SA@NCDs-5 hydrogel adsorbent greatly improved the adsorption capacity for phosphorus compared with the La (III)-free adsorbent, and the adsorption amount can reach 9.64mg-P/g. The SA@NCDs complex hydrogels for rare earth adsorption were prepared by introducing NCDs rich in amino group into SA hydrogels. The introduction of NCDs increases the adsorption sites of hydrogels, and also overcomes the problem that NCDs itself is difficult to recover in wastewater treatment applications. The lanthanide adsorbed material has a stable structure and can be used to remove phosphorus to deal with waste using the waste. It indicates the SA@NCDs hydrogel composite adsorbent have good potential for wastewater treatment.

A comparative study on the malachite green dye adsorption of chemically synthesized and green MgFe2O4 nanoparticles using gerbera floral waste extract.

The situation of discharging a large amount of dyes from the textile industries has caused many adverse effects on human health and the ecosystems. Emerging bio-nanomaterials represent a new trend in efficient dye removal in aqueous media. Herein, we mention that MgFe2O4 bioprepared using gerbera extract has been successfully used to adsorb malachite green (MG) in water. A comparison was made to determine the dye removal efficiency between biogenic MgFe2O4 (MFOB) and chemical MgFe2O4 (MFOC). The spherical MFOB material exhibited a large surface area of 85.0 m2 g-1 and high crystallinity. The obtained outcomes showed that the highest adsorption capacity of MG dye was 584.49 mg g-1 at a MFOB dose of 0.05 g L-1 and MG concentration of 10 mg L-1. Higher correlation coefficients in the Langmuir isotherm suggested monolayer adsorption of MG. The Box-Behnken design and response surface method were established to optimize MG removal percentage under the conditions, i.e., initial MG concentration (10-30 mg L-1), adsorbent dose (0.02-0.08 g L-1), and pH of dye solution (6-8). MFOB had good reusability with high removal efficiencies after three continuous cycles. Post reuse, this adsorbent still showed excellent stability through the verification of their structural properties in comparison with fresh MFOB, showing potential for practical applications.

Gold recovery from electronic wastes using a solvent extraction/selective back-extraction strategy

ABSTRACT The present lab-scale investigation describes a simple and efficient approach to the selective solvent extraction and recovery of gold, and copper as a by-product, from Waste Printed Circuit Boards (WPCBs) of different brands of used computers. The process comprised of three steps; leaching of scraps in aqua regia, solvent extraction process under optimized conditions, and ultimately selective back-extraction. The analysis of leach solution by inductively coupled plasma revealed, in addition to gold (0.14 wt%), copper (40.0 wt%), tin (11.9 wt%), and Ni (2.3 wt%) were the other main metals in the WPCBs. A solvent extraction procedure using trioctylamine, as extractant, dissolved in kerosene was employed for the extraction of gold as its anionic chloride-complexes from the leach liquor. The parameters affecting this process including hydrochloric acid concentration, equilibrium time, extractant concentration, initial gold concentration in the sample solution, and the aqueous/organic volume ratio were optimized by means of the statistical technique response surface methodology (RSM). Under the optimized extraction conditions, 99.6% of gold and 23.4% of copper were transferred into the organic phase, while the extracted percentage of other metal ions were negligible. Selective back-extraction by the solution 0.1 M NaOH resulted in the selective precipitation of copper, while the raffinate contained just gold ions.

MOF-derived Co-Ni layered double hydroxides/polyethyleneimine modified chitosan micro-nanoreactor for high-efficiency capture of uranium from seawater

The preparation of powder adsorbent into microsphere adsorbent is one of the effective methods for the industrialization of uranium extraction from seawater. Herein, a MOF-derived Co-Ni layered double hydroxides/polyethyleneimine modified chitosan micro-nanoreactor (DNPM) was prepared by a simple method in this work. The microstructure and chemical structure of DNPM were comprehensively characterized. The pH value, adsorption time, initial solution concentration, temperature, competitive ions, regeneration performance, and bed column heights were investigated for the adsorption performance of DNPM by batch adsorption and fixed-bed column continuous adsorption experiments. When the contact time was 8 h, the initial concentration was 150 mg/L, and the pH value was 6, the adsorption capacity of DNPM was 334.67 mg/g. The uranium adsorption by DNPM fits with the pseudo-second-order kinetic and Langmuir models, which was a spontaneous and endothermic process. In addition, DNPM has good adsorption selectivity and reusability. The fixed-bed column continuous adsorption experiment shows that the adsorption capacity increased with the increase of bed column height. The adsorption mechanism can be attributed to coordination chelation and electrostatic interaction. In general, this work provides an effective strategy for developing environmentally friendly uranium adsorbent that can be industrially used.

Adsorption of Methyl Red and Methylene Blue on Carbon Bioadsorbents Obtained from Biogas Plant Waste Materials.

In this study, biocarbon was obtained from the waste material corn digest. Carbon adsorbents were obtained by physical activation of the precursor with CO2. Detailed physicochemical characterization of the biocarbon was carried out using low-temperature nitrogen adsorption/desorption, Boehm titration, zero-charge point (pHpzc) and iodine number. In addition, the sorption capacity of the biocarbon agents towards an aqueous solution of methylene blue and methyl red was determined, and the kinetics of the adsorption process were determined. The biocarbon adsorbents were characterized by an average developed specific surface area covering the range from 320 to 616 m2/g. The sorption capacity of the biocarbon adsorbents against methylene blue ranged from 40 mg/g to 146 mg/g, and for methyl red it covered the range from 31 mg/g to 113 mg/g. It was shown that the efficiency of organic dye removal by the obtained biocarbons depends on the initial concentration of the adsorbate solution, its mass, shaking rate, adsorbent-adsorbate contact time and temperature. The results obtained from the Langmuir and Freundlich kinetic models showed that the Langmuir model is the most suitable model for describing the adsorption of the studied pollutants on biocarbon. In turn, the adsorption kinetics of dyes is described according to the pseudo-second-order model. Adsorption studies also showed that as the process temperature increases, the removal efficiency of methylene blue and methyl red increases.

Adsorptive efficiency of hull-based activated carbon toward copper ions (Cu2+) removal from aqueous solution: Kinetics, modelling and statistical analysis

Activated carbons represent powerful materials for water depollution. In this study, two carbon materials were synthesized by a simple and eco-friendly method using Neem and Hyphaene thebaica biomass waste. The material preparation aimed to reach high surface activity and low cost in order to develop an adsorbent for the removal of harmful substances from water, such as heavy metals. The prepared carbon materials were characterized using various techniques, including Brunauer-Emmett-Teller (BET) specific surface area, thermogravimetric analyses (TGA), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and Fourier transform infrared spectroscopy (FT-IR). The adsorption of Cu (II) ions on activated carbon from Neem (CAN) and Hyphaene thebaica (CAH) hulls was systematically investigated using a batch method by varying several key operational parameters such as contact time, pH, adsorbent dose and the effect of concentration. The results obtained from the study indicated that the maximum uptake capacity was 277 mg/g for CAN and 210 mg/g for CAH at pH 5 after 15 min of equilibrium time in contact with 500 mg/L of initial concentration of copper ions solution. Marczewski-Jaroniec and Sips isotherm models fitted well the experimental data with high R2, adj-R2 and less value or errors analysis for either CAN or CAH. Besides, the kinetic study showed that the adsorption followed a pseudo-first-order model for CAN and a pseudo-second-order for CAH. Thus, this study shows that Neem and Hyphaene thebaica hulls represent a valuable biomass source for the production of activated carbon for heavy metal remediation.

Adsorption of Basic Yellow 28 and Basic Blue 3 Dyes from Aqueous Solution Using Silybum Marianum Stem as a Low-Cost Adsorbent.

In the present study, the ability of an adsorbent (SLM Stem) obtained from the stem of the Silybum Marianum plant to treat wastewater containing the cationic dyes basic blue 3 (BB3) and basic yellow 28 (BY28) from aqueous solutions was investigated using a batch method. Then, the SLM Stem (SLM Stem-Natural) adsorbent was carbonized at different temperatures (200-900 °C) and the removal capacity of the products obtained for both dyes was examined again. The investigation continued with the product carbonized at 800 °C (SLM Stem-800 °C), the adsorbent with the highest removal capacity. The dyestuff removal studies were continued with the SLM Stem-Natural and SLM Stem-800 °C adsorbents because they had the highest removal values. The surface properties of these two adsorbents were investigated using IR, SEM, and XRD measurements. It was determined that the SLM Stem-Natural has mainly non-porous material, and the SLM Stem-800 °C has a microporous structure. The optimal values for various parameters, including adsorbent amount, initial dye solution concentration, contact time, temperature, pH, and agitation speed, were investigated for BY28 dye and were 0.05 g, 15 mg/L, 30 min, 40 °C, pH 6 and 100 rpm when SLM Stem-Natural adsorbent was used and, 0.15 g, 30 mg/L, 30 min, 40 °C, pH 10, and 150 rpm when SLM Stem-800 °C adsorbent was used. For BB3 dye, optimal parameter values of 0.20 g, 10 mg/L, 30 min, 25 °C, pH 7, and 100 rpm were obtained when SLM Stem-Natural adsorbent was used and 0.15 g, 15 mg/L, 40 min, 40 °C, pH 10, and 100 rpm when SLM Stem-800 °C adsorbent was used. The Langmuir isotherm described the adsorption process best, with a value of r2 = 0.9987. When SLM Stem-800 °C adsorbent was used for BY28 dye at 25 °C, the highest qm value in the Langmuir isotherm was 271.73 mg/g. When the study was repeated with actual water samples under optimum conditions, the highest removal for the BY28 dye was 99.9% in tap water with the SLM Stem-800 °C adsorbent. Furthermore, the reuse study showed the adsorbent's efficiency even after three repetitions.

Membrane Functionalization Approaches toward Per- and Polyfluoroalkyl Substances and Selected Metal Ion Separations.

Adsorption and ion exchange technologies are two of the most widely used approaches to separate pollutants from water; however, their intrinsic diffusion limitations continue to be a challenge. Pore functionalized membranes are a promising technology that can help overcome these challenges, but the extents of their competitive benefits and broad applicability have not been systematically evaluated. Herein, three types of adsorptive/ion exchange (IX) polymers containing strong/weak acid, strong base, and iron-chitosan complex groups were synthesized in the pores and partially on the surface of microfiltration (MF) membranes and tested for the removal of organic and inorganic cations and anions from water, including arsenic, per- and polyfluoroalkyl substances (PFAS), and calcium (hardness). When directly compared with beads (0.5-6 mm) and crushed resins (0.05 mm), adsorptive/IX pore-functionalized membranes demonstrated an increased relative sorption capacity, up to 2 orders of magnitude faster kinetics and the ability to regenerate up to 70-100% of their capacity while concentrating the initial solution concentration up to 12 times. The simple and versatile synthesis approach used to functionalize membranes, notably independent of the polymer type of the MF membrane, utilized pores throughout the entire cross section of the membrane to immobilize the polymers that contain the functional groups. Utilizing the pore volume of commercial membranes (6-112 mL/m2), the scientific weight capacity of the polymer (3.1-11.5 mequiv/g), and the synthesis conditions (e.g., monomer concentration), the theoretical adsorption/IX capacities per area of the membranes were calculated to be as high as 550 mequiv/m2, substantially higher than the 175 mequiv/m2 value needed to compete with commercially available IX resins. This work therefore shows that pore functionalized membranes are a promising path to tackle water contamination challenges, lowering separation diffusion limitations.

Biomass activated carbon supported Keggin-type polyoxometalate as an electrode material for high-performance acidic aqueous supercapacitors

Activated carbon (SSAC-OP) with micropore and mesopore was prepared by using soybean straw as a carbon source. Redox-active H3PMo12O40 (PMo12) was introduced into SSAC-OP by solution impregnation to obtain composite PMo12/SSAC-OP. The effect of loading amount of PMo12 on the supercapacitive performance of the composite was investigated. BET and EDS results confirmed that PMo12 is adsorbed in the micropores of 1–2 nm and mesopores of SSAC-OP, as well as on the carbon wall of SSAC-OP. Meanwhile, SSAC-OP with positive charge is more firmly connected with PMo12 anions via the effect of electrostatic attraction. CV and GCD test results proved that the composite materials have both electric double layer capacitance and pseudocapacitance characteristics. The CV curve of 10-PMo12/SSAC-OP obtained from SSAC-OP impregnating the initial concentration of PMo12 solution of 10 mM shows four pairs of obvious reversible redox peaks, which indicates that the protonation of PMo12 anion in the reduction process is sufficient. The composite 10-PMo12/SSAC-OP has a specific capacitance as high as 397.02F g−1 at scan rate of 5 mV s−1. The assembled symmetric supercapacitor delivers an energy density of 23.90 Wh kg−1 under the power density of 1016.05 W kg−1, with 97.96 % capacitance retention after 10,000 cycles at 3 A g−1.

Facile design and fabrication of RP/ZnIn2S4 composite photocatalysts with efficient removal of antibiotics under visible-light irradiation

Efficient photocatalysts with visible light irradiation have a bright future in practical environmental remediation. ZnIn2S4 is a promising environmentally friendly visible-light photocatalyst, due to its appropriate narrow band gap and excellent chemical stability. In this research, the RP/ZnIn2S4 composites with flower spheroidal morphology were synthesized by loading RP onto the surface of ZnIn2S4 via a one-pot hydrothermal process. The experimental results show that the tetracycline (TC) degradation efficiency of RP(1 wt%)/ZnIn2S4 was up to 85.1 %, compared with pure RP, ZnIn2S4, and other series of RP/ZnIn2S4 composites. The optimal degradation conditions were as following: 1 wt% RP modification amount, 30 mg catalyst amount, 30 mg/L initial TC solution concentration, and the initial reaction pH of 7. At the same time, good repeatability and stability of RP(1 wt%)/ZnIn2S4 toward TC removal confirm its potential value for practical applications. In addition, the degradation efficiency of RP(1 wt%)/ZnIn2S4 for rifamycin and ofloxacin under the similar conditions was 80.2 % and 65.3 %, respectively, indicating the universal application of RP/ZnIn2S4 for degradation of different antibiotic pollutants. The possible photocatalytic mechanism was proposed based on the trapping experiment and ESR test. The RP(1 wt%)/ZnIn2S4 composite photocatalytic materials with high efficiency and stability are expected to contribute to the exploration of the environmental protection field.

Dynamics of Drop Formation in the Presence of Interfacial Mass Transfer.

The dynamics of drop formation have been investigated in the presence of interfacial mass transfer through controlled flow visualization experiments. The mixtures of n-hexane (solvent) and acetone (solute) were used as a dispersed phase, having different initial compositions varying over a broad range. Drops were formed at the submerged position in the continuous phase (water) at the same operating flow conditions. The unsteady force balance model is developed to analyze the implications of the simultaneously occurring interfacial transfer of the solute on the formation dynamics in real time, and predictions are validated with experimental results. Based on initial compositions, the analysis of the transient drop shape shows a sharp transition in the drop formation regime. At lower initial solute concentrations, i.e., ϕ0 < 0.2, axisymmetric drop formation occurs and the interfacial solute transfer has negligible effects on the formation dynamics. Over an intermediate range of solute concentrations, i.e., 0.2 < ϕ0 < 0.5, Marangoni instability is triggered along the evolving interface, and therefore, the interface deformations and contractions occur during the drop formation. At ϕ0 = 0.5, the drop takes highly nonaxisymmetric shapes and remains away from equilibrium until its detachment from an orifice. For ϕ0 > 0.5, the spontaneous ejection of plumes of the solute results in the rapid generation of multiple droplets of smaller size. This work shows that higher solute concentration gradients not only lead to faster solute transport but also induce strong interfacial instability simultaneously. Thus, the coupled effects of transient change in composition and fluid properties govern the drop size and its formation time in such systems under non-equilibrium.

Hydroxyapatite nanoparticles decorated with metal–organic framework, Co‐Cu/ZIF@HAp, and evaluation of photocatalytic performance of the prepared nanocomposite in the degradation of organic pollutants

In this study, a novel hydroxyapatite (HAp)‐based composite, Co‐Cu/ZIF@HAp, was constructed through in situ growth and simultaneous sonication followed by magnetic string. Herein, the HAp‐based nanocomposite was obtained in which HAp was coated with cobalt–copper bimetallic zeolitic imidazolate framework (ZIF) in one‐pot synthesis method. The as‐synthesized composite was characterized by PXRD, FTIR, FE‐SEM, EDS, HR‐TEM, TGA‐DTG, XPS, BET, and UV‐DRS techniques, which suggested that HAp was well coated with bimetallic ZIF. The prepared composite was utilized as a catalyst in degradation of organic pollutants. Removal of organic pollutants such as organic dyes has become indispensable due to their higher stability, toxicity, and mutagenic nature. Two commonly found organic dyes, namely, Eosin Yellow (EY) and Brilliant Green (BG), were chosen for the investigation of photocatalytic activity of the as‐prepared catalyst. The degradation process was carried out under solar radiation, and there was no utilization of any oxidizing and reducing agent. Several parameters such as amount of catalyst dose, initial concentration of the dye solution, and effect of different pH conditions were evaluated for better understanding of photocatalytic performance of Co‐Cu/ZIF@HAp composite. Both EY and BG dyes were almost degraded up to 98.3% and 99.5%, respectively, within 50 min by the as‐prepared nanocomposite. Also, quenching test was performed that confirmed the formation of superoxide radicals (O2−.) as reactive oxygen species (ROS) in the photodegradation process. The as‐synthesized catalyst was repeatedly used for five times to ascertain the stability and reusability of catalyst.

Mechanistic insight and optimisation of hydrothermally pre-treated biowaste-derived biochar for saline water treatment

The valorisation of oil palm empty fruit bunch is challenging due to its poor surface functionalities, which require a comprehensive pre-treatment process. To ensure efficient valorisation of the agricultural waste, the biochar derived from empty fruit bunch is subjected to hydrothermal nitric acid pre-treatment to act as an adsorbent for sodium ions removal from the saline solution. For this newly developed adsorbent, the adsorption study provides important information on the adsorption behaviour of sodium ions and the optimum conditions for sodium ions removal, which is crucial for effective process design and operation control during practical applications. Physicochemical characterisation revealed the successful adsorption of sodium ions by Hydrothermal Nitric acid Pre-treated EFB Biochar (HNO3 EFB-BC. The highest sodium ions removal efficiency of HNO3 EFB-BC (92.04%) was achieved under the optimum reaction conditions: 0.39 M initial concentration of the saline solution, 4.96 g of HNO3 EFB-BC, contact time of 17.4 h and solution pH of 7.46. Upon process optimisation, the adsorption capacity of HNO3 EFB-BC towards sodium ions improved remarkably (p < 0.05) from 78.34 mg g-1 to 166.45 mg g-1. The adsorption isotherm and kinetic study are consistent with the Langmuir and pseudo-second-order models, implying a monolayer chemisorption-dominated adsorption process. The promising sodium ions adsorption capacity of HNO3 EFB-BC can be attributed to the enhanced surface functionalities of the adsorbent. The molecular modelling using the density functional theory approach has successfully identified the nitro group as the most favourable functional group in producing the charges sites for sodium ions adsorption, with the most stable reaction route between HNO3 EFB-BC and sodium ions being identified. This study highlighted the density functional theory approach as a tool for identifying the specific functional groups with enhanced adsorption capability for saline water treatment and provides a reference value for removing sodium ions in the presence of other cationic pollutants.

Efficient adsorption of azo anionic dye Congo Red by micro-nano metal-organic framework MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge: Preparation, characterization and adsorption performance

Micro-nano metal-organic framework (MIL-68(Fe)) for efficient adsorption of azo anionic dye Congo red (CR) was successfully prepared by one-step hydrothermal method under acidic environment. And a MIL-68(Fe)/chitosan composite sponge (MIL-68(Fe)/CS) was prepared under the coating of chitosan (CS). After comparing the performance of MIL-68(Fe) and MIL-68(Fe)/CS, we focus on exploring MIL-68(Fe)/CS. It ensured the CR removal efficiency while reaching the adsorption equilibrium faster than MIL-68(Fe), and solved the defect that the powder was difficult to be stripped by water after adsorption. The physicochemical properties and surface morphology of the adsorbent were characterized by SEM, FTIR, XRD, TGA, BET, and Zeta potential. The effects of pH, contact time, adsorbent dosage, initial solution concentration and temperature on the adsorption performance of the adsorbent were systematically analyzed. The pseudo-second-order model and the Sips model were most consistent for the adsorption process, indicating that the adsorption process of MIL-68(Fe)/chitosan composite sponge on CR is a complex physicochemical process. The removal rates of CR by MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge reached the maximum values of 99.55 % and 99.51 % at 318 K, respectively. And the maximum adsorption capacity of CR by MIL-68(Fe)/chitosan composite sponge at 318 K was 1184.16 mg·g−1. After six cycles of adsorption and desorption, the removal rate of CR was still higher than 80 %. The synergistic effects of π-π stacking, electrostatic interactions, hydrogen bonding and pore filling have important effects on CR removal.

Constructing novel inorganic-organic α-Fe2O3/SNW-1 Z-scheme heterojunction for Methylene Blue photodegradation

A novel organic/inorganic heterostructured photocatalyst binary nanocomposite was typically prepared by the solvothermal method. The overwhelming superiority of this composite has been confirmed by spectroscopic and characterization methods, where the addition of α-Fe2O3 reduced the agglomeration of the Schiff-based covalent organic framework SNW-1 and significantly increased the specific surface area. The effects of operating parameters such as catalyst dosage, initial solution concentration, and pH on photocatalytic degradation of methylene blue (MB) dye were carefully investigated. Among them, a UV irradiation time of 80 min, a powder dose of 0.6 g/L, and pH=2 were the best choice. Under these favorable conditions, the α-Fe2O3/SNW-1 system exhibited excellent photocatalytic performance, and the degradation rate of MB reached more than 95%. In addition, the photocatalytic degradation efficiency of the pollutants acid orange 7 (AO7), rhodamine-B (RhB), and acid red (ArB) comfortably reached 92%, 92%, and 91%, respectively. After five cycles of testing, the prepared photocatalyst showed good stability and reusability. Through energy band calculation, free radical quenching experiment, and electron paramagnetic resonance (ESR) study, it was discovered that the main active substances were ·O2- and ·OH, and the photogenerated holes and electrons also participated in the photocatalytic reaction. The Z-scheme charge transfer mechanism of α-Fe2O3/SNW-1 was proposed. Photoelectric chemical tests further demonstrated the extraordinary photocatalytic activity, low internal resistance, and high carrier separation capability of the binary nanocomposites. This study presents the potential application of high-performance photocatalysts for the removal of organic dyes in water purification.

Removal of Congo Red Dye Using Ficus benghalensis-Assisted Copper Oxide Nanoparticles

Novel water purification technologies are emerging to satisfy the requirement of clean drinking water for human life. The development of long-term water treatment systems is a serious concern. In this regard, nanotechnology holds enormous promise for improving the effectiveness and efficiency of polluted water remediation. The goal of this work was to create a simple and effective water purification system that used cost-effective, durable, and environmentally friendly novel materials. Green nanoparticle synthesis has emerged as a result of recent advancements in environmentally friendly technologies. The use of plant extract to synthesize nanoparticles is thought to be an incredible green strategy.&#x0D; In the present study, leaf extract of Ficus benghalensis was chosen to synthesize the low cost and novel copper oxide (CuO) nanoparticles. The aim was to investigate the ability of these novel nano particles in removing Congo red dye from water. Various parameters including contact time, adsorbent dosage, initial dye concentration and pH of dye solution that affect the adsorption were optimized by carrying out batch adsorption experiments. The mechanism of pseudo-first-order, pseudo-second-order, Langmuir equilibrium isotherm, and Freundlich isotherm was investigated using kinetic and equilibrium experimental data. These models gave an insight into the adsorption kinetics and adsorption mechanism. The pH effect revealed that Congo red dye being an acidic dye showed good adsorption at acidic pH. The findings of this work show that copper oxide nanoparticles are promising adsorbents for the removal of Congo red dye from aqueous based system.