Competitive removal of hazardous dyes from aqueous solution by MIL-68(Al): Derivative spectrophotometric method and response surface methodology approach

Natural and anthropogenic dissolved organic matter in landfill leachate: Composition, transformation, and their coexistence characteristics

A large number of natural and anthropogenic wastes were landfilled, and dissolved organic matter (DOM) were formed during landfill. However, the composition, transformation, and coexistence characteristics of natural and anthropogenic DOM in leachate remain unclear. Fourier transform ion cyclotron resonance mass spectrometry, size exclusion chromatography, gas chromatography coupled with mass spectrometry, and three-dimensional excitation-emission matrix spectrum were employed to clarify comprehensively the abovementioned question. The results showed that natural DOM in young leachate constituted mainly straight-chain organic acids, protein substances, and building blocks of humic substances (BB). Straight-chain organic acids vanished in old leachates, and the concentration of protein substances and BB decreased from 44% to 26% and from 47% to 12%, respectively, while CHON and CHONS were degraded to CHO and CHOS during the process. As to anthropogenic DOM, its types and relative content in leachate increased during landfill, and aromatic acids, terpenes, halogenated organics, indoles, and phenols became the main organic components in old leachate. Compared to natural DOM, anthropogenic DOM was degraded slowly and accumulated in leachate, and some of the natural DOM facilitated the dechlorination of dichlorinated organic compounds. This study demonstrates that landfill led to an increase in humic substances and halogenated organic compounds in old leachate, which was intensified with concentrated leachate recirculation.

A new tannin-based adsorbent synthesized for rapid and selective recovery of palladium and gold: Optimization using central composite design

A tannin-based adsorbent was synthesized by pomegranate peel tannin powder modified with ethylenediamine (PT-ED) for the rapid and selective recovery of palladium and gold. To characterize PT-ED, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS-Mapping), and Fourier transform infrared spectroscopy (FT-IR) were used. Central composite design (CCD) was used for optimization. The kinetic, isotherm, interference of coexisting metal ions, and thermodynamics were studied. The optimal conditions, including Au (III) concentration = 30 m g L - 1 , Pd (II) concentration = 30 m g L - 1 , adsorbent mass = 26 mg, pH = 2, and time = 26 min with the sorption percent more than 99 %, were anticipated for both metals using CCD. Freundlich model and pseudo-second-order expressed the isotherm and kinetic adsorption of the both metals. The inhomogeneity of the adsorbent surface and the multi-layer adsorption of gold and palladium ions on the PT-ED surface are depicted by the Freundlich model. The thermodynamic investigation showed that P d 2 + and A u 3 + ions adsorption via PT-ED was an endothermic, spontaneous, and feasible process. The maximum adsorption capacity of P d 2 + and A u 3 + ions on PT-ED was 261.189 m g g - 1 and 220.277 m g g - 1 , respectively. The probable adsorption mechanism of P d 2 + and A u 3 + ions can be ion exchange and chelation. PT-ED (26 mg) recovered gold and palladium rapidly from the co-existing metals in the printed circuit board (PCB) scrap, including Ca, Zn, Si, Cr, Pb, Ni, Cu, Ba, W, Co, Mn, and Mg with supreme selectivity toward gold and palladium. The results of this work suggest the use of PT-ED with high selectivity and efficiency to recover palladium and gold from secondary sources such as PCB scrap.

Interaction of a Porphyrin Aluminum Metal-Organic Framework with Volatile Organic Sulfur Compound Diethyl Sulfide Studied via In Situ and Ex Situ Experiments and DFT Computations

The study presents complementary experiments and quantum chemical DFT computations to reveal the molecular-level interactions of an advanced nanomaterial, porphyrin aluminum metal-organic framework (compound 2), with the volatile organic sulfur compound diethyl sulfide (DES). First, the intermolecular host-guest interactions during the sorption of DES were explored under dynamic conditions, using the vapor of DES in flowing air. The in situ time-dependent ATR-FTIR spectroscopy in a controlled atmosphere was significantly improved though the use of a new facilely built spectroscopic mini-chamber. The binding site of DES in compound 2 involves the μ(O-H) and COO- groups of the linker of the sorbent. Further, the chemical kinetics of the sorption of DES was investigated, and it follows the Langmuir adsorption kinetic model. That is, depending on the time interval, the process obeys either the pseudo-first- or pseudo-second-order rate law. For the Langmuir adsorption of the pseudo-first order, the rate constant is robs = 0.165 ± 0.017 min-1. Next, the interaction of compound 2 with the saturated vapor of DES yields the adsorption complex compound 3 [Al-MOF-TCPPH2]2(DES)7. The adsorbed amount of DES is very large at 36.5 wt.% or 365 mg/g sorbent, one of the highest values reported on any sorbent. The molecular modes of bonding of DES in the complex were investigated through quantum chemical DFT computations. The adsorption complex was facilely regenerated by gentle heating. The advanced functional material in this work has significant potential in the environmental remediation of diethyl sulfide and related volatile organic sulfur compounds in air, and it is an interesting target of mechanistic studies of sorption.

Preparation of a Multifunctional and Multipurpose Chitosan/Cyclodextrin/MIL-68(Al) Foam Column and Examining Its Adsorption Properties for Anionic and Cationic Dyes and Sulfonamides

A multifunctional cylindrical hybrid foam column, referred to as the chitosan/cyclodextrin/MIL-68(Al) (CS/CD/MIL-68(Al)) foam column, was prepared for the first time. The prepared foam column could be used for the adsorption/removal of hydrophilic and hydrophobic contaminants by different forms. Here, it was placed in hydrophilic dye solutions to investigate the adsorption behavior of methylene blue and trypan blue. The adsorption process followed the pseudo-second-order kinetic model with R2 ranging from 0.9983 to 0.9998 for methylene blue and from 0.9993 to 1.0000 for trypan blue, and the adsorption process was consistent with the Langmuir isothermal model with R2 greater than 0.96. The RL values for methylene blue and trypan blue were 0.8871 and 0.5366, respectively, which were present between 0 and 1, indicating that the adsorption behaviors of the two dyes onto the CS/CD/MIL-68(Al) foam column were favorable. The maximum adsorption capacities (Qm) of methylene blue and trypan blue were 60.61 and 454.55 mg/g at 298 K, respectively. Also, the CS/CD/MIL-68(Al) foam column was spun into a syringe and used to adsorb trace hydrophobic sulfonamides from water in the form of filtration. The porous structure impeded the need for any external force and equipment, allowing the water sample to pass through the foam column smoothly. The conditions of the CS/CD/MIL-68(Al) foam column were optimized. The adsorption was carried out under the condition of pH = 4, the amount of the adsorbent was two foam columns, and no salt was added. It was found that the removal rate of the CS/CD/MIL-68(Al) foam column for six sulfonamides was 100%, and it could be reused at least five times. Therefore, this CS/CD/MIL-68(Al) foam column had a simple preparation method, offered a flexible and diverse form of use, was nonpolluting, biodegradable, and reusable, and could have a wider application in the field of environmental pollutant removal and adsorption.

Investigation of kinetics, isotherms, thermodynamics and photocatalytic regeneration of exfoliated graphitic carbon nitride/zeolite as dye adsorbent

A novel exfoliated graphitic carbon nitride and clinoptilolite nanocomposites (Ex.g-C3N4/CP and g-C3N4/CP with a various ratios of g-C3N4 to CP) were prepared by facile method. This study evaluates the adsorption of methylene blue (MB) on the surface of synthesized adsorbents. The as-prepared composites were characterized by XRD, FT-IR, FESEM, BET and DRS. Batch experiments were carried out under various conditions, such as the amount of adsorbent and solution pH. The optimum batch experimental conditions were found under the response surface methodology. The Ex.g-C3N4/CP presented maximum removal of MB as compared to others. The removal efficiency of the as-prepared nanocomposite was significantly elevated owing to the synergistic effects. The adsorption capacities of MB (10 ppm) on Ex.g-C3N4/CP was 54.3 mg/g. The adsorption process by both composites (g-C3N4/CP and Ex.g-C3N4/CP) showed well-fitting with the Elovich kinetic model, and Langmuir isotherm. The thermodynamic study suggested that the adsorption of MB was a spontaneous and endothermic process. The reusability of g-C3N4/CP1:2 and Ex. g-C3N4/CP in removing of MB (10 ppm, pH = 9) was studied by photocatalytic regeneration under visible irradiation for three consecutive cycles. The results obtained from the experimental analyses showed that the removal of MB was easy treatment, eco-friendly, and high yield.

Comprehensive insight into adsorption of chlortetracycline hydrochloride by room-temperature synthesized water-stable Zr-based metal-organic gel/sodium alginate beads

Chlortetracycline hydrochloride (CTC) is one of the prevailing antibiotic pollutants that harm both environmental ecosystem and human health. Herein, Zr-based metal-organic gels (Zr-MOGs) with lower-coordinated active sites and hierarchically porous structures are fabricated via a facile straightforward room-temperature strategy for CTC treatment. More importantly, we incorporated the powder Zr-MOGs into low-cost sodium alginate (SA) matrix to achieve shaped Zr-based metal-organic gel/SA beads for enhancing the adsorption ability and ameliorating the recyclability. The Langmuir maximum adsorption capacities of Zr-MOGs and Zr-MOG/SA beads could reach 143.9 mg/g and 246.9 mg/g, respectively. What's more, in the manual syringe unit and continuous bead column experiments, Zr-MOG/SA beads could achieve an eluted CTC removal ratio as high as 93.6% and 95.5% in the real water sample, respectively. On top of that, the adsorption mechanisms were put forward as a combination of pore filling, electrostatic interaction, hydrophilic-lipophilic balance, coordination, π-π interaction as well as hydrogen bonding interaction. This study outlines a workable strategy for the facile preparation of candidate adsorbents for wastewater treatment.

Novel strategies for the formulation and processing of aluminum metal-organic framework-based sensing systems toward environmental monitoring of metal ions

Aluminum is a relatively inexpensive and abundant metal for the mass production of metal-organic frameworks (MOFs). Aluminum-based MOFs (Al-MOFs) have drawn a good deal of research interest due to their unique properties for diverse applications (e.g., excellent chemical and structural stability). This review has been organized to highlight the current progress achieved in the synthesis/functionalization of Al-MOF materials with the special emphasis on their sensing application, especially toward metal ion pollutants in the liquid phase. To learn more about the utility of Al-MOF-based sensing systems, their performances have been evaluated for diverse metallic components in reference to many other types of sensing systems (in terms of the key quality assurance (QA) criteria such as limit of detection (LOD)). Finally, the challenges and outlook for Al-MOF-based sensing systems are discussed to help expand their real-world applications.

Integration of ozonation with water treatment for pharmaceuticals removal from Arroio Diluvio in southern Brazil

Pharmaceutical compounds can reach water bodies through sewage systems. The process of water treatment is insufficient for the removal of these contaminants. The ozonation has great potential to be integrated into the treatment, since it promotes the reduction of pharmaceuticals, reduces the generation of disinfection byproducts and can reduce operational costs. In this work, the integration of the ozonation process with water treatment was studied. The ozone was applied in the pre-oxidation and intermediate ozonation stages, to evaluate the dependence of different variables. Water samples were collected from Arroio Diluvio, a river of the city of Porto Alegre (Brazil). The doses of ozone were maintained between 0.5 and 1.0 mgO₃ L^-1 while the coagulant was between 25 and 150 mg·L^-1. Pre-ozonation resulted in a removal of pharmaceuticals at pH 10.0, time of 15 min and coagulant concentration of 52.5 mgL^-1. The intermediate ozonation provided a removal with pH 10.0 and a time of 5 min of bubbling. Based on the results, it was confirmed that the synergy of the ozonation process with conventional water treatment is an effective, sensitive and fast method for the removal of pharmaceuticals from the aqueous medium.

Activation of bisulfite by LaFeO3 loaded on red mud for degradation of organic dye

In this study, red mud (RM) was used as a support for LaFeO₃ to prepare LaFeO₃-RM via the ultrasonic-assisted sol-gel method for the removal of methylene blue (MB) assisted with bisulfite (BS) in the aqueous solution. Characterization by scanning electron microscopy and the Brunauer-Emmett-Teller method indicated that LaFeO₃-RM exhibited a large surface area and porous structure with a higher pore volume (i.e. 10 times) compared with the bulk LaFeO₃. The XRD, XPS and FTIR results revealed that the support of porous RM not only dispersed LaFeO₃ particles but also increased Fe oxidation capability, oxygen-containing functional groups and chemically adsorbed oxygen (from 44.3% to 90.3%) of LaFeO₃-RM, which improved the catalytic performance in structure and chemical composition. MB was removed through the synergistic effect of adsorption and catalysis, with MB molecules first absorbed on the surface and then degraded. The removal efficiency was 88.19% in the LaFeO₃-RM/BS system under neutral conditions but only 27.09% in the LaFeO₃/BS system. The pseudo-first-order kinetic constant of LaFeO₃-RM was six times higher than that of LaFeO₃. Fe(III) in LaFeO₃-RM played a key role in the activation of BS to produce SO 4 ⋅ - by the redox cycle of Fe(III)/Fe(II). Dissolved oxygen was an essential factor for the generation of SO 4 ⋅ - . This work provides both a new approach for using porous industrial waste to improve the catalytic performance of LaFeO₃ and guidance for resource utilization of RM in wastewater treatment.

Facile fabrication of amino-functionalized MIL-68(Al) metal-organic framework for effective adsorption of arsenate (As(V))

An amino-functionalized MIL-68(Al) metal–organic framework (amino-MIL-68(Al) MOF) was synthesized by solvothermal method and then characterized by FESEM, XRD, FTIR, EDX-mapping, and BET-BJH techniques. In order to predict arsenate (As(V)) removal, a robust quadratic model (R² > 0.99, F-value = 2389.17 and p value < 0.0001) was developed by the central composite design (CCD) method and then the genetic algorithm (GA) was utilized to optimize the system response and four independent variables. The results showed that As(V) adsorption on MOF was affected by solution pH, adsorbent dose, As(V) concentration and reaction time, respectively. Predicted and experimental As(V) removal efficiencies under optimal conditions were 99.45 and 99.87%, respectively. The fitting of experimental data showed that As(V) adsorption on MOF is well described by the nonlinear form of the Langmuir isotherm and pseudo-second-order kinetic. At optimum pH 3, the maximum As(V) adsorption capacity was 74.29 mg/g. Thermodynamic studies in the temperature range of 25 to 50 °C showed that As(V) adsorption is a spontaneous endothermic process. The reusability of MOF in ten adsorption/regeneration cycles was studied and the results showed high reusability of this adsorbent. The highest interventional effect in inhibiting As(V) adsorption was related to phosphate anion. The results of this study showed that amino-MIL-68(Al) can be used as an effective MOF with a high surface area (> 1000 m²/g) and high reusability for As(V)-contaminated water.

Nitric oxide detection using catalytic properties of CuCo-PTC metal organic framework

As a vital gaseous signal molecule involved in various physiological and pathological processes, nitric oxide (NO) has attracted extensive attention in the last few decades. In this work, a copper and cobalt element-doped, biphenyl-(3, 4', 5)-tricarboxylic acid (H₃PTC)-synthesized metal organic framework (CuCo-PTC MOF) composite with catalytic ability was synthesized by solvothermal method. The material can catalyse the oxidation of o-phenylenediamine (OPD) groups by hydrogen peroxide (H₂O₂) to form fluorophores (OPDox) with yellow fluorescence emission and greatly improves its reaction rate. In the presence of NO, OPD will react with NO to produce N-(2-hydrazinophenyl) methylamine, and the group will not react with H₂O₂. Therefore, the concentration of NO can be measured indirectly by comparing the changes of fluorescence intensity in the presence and absence of NO. As the concentration of NO changes, the change of solution colour (from bright yellow to colourless) can also be observed under a 365-nm UV lamp. Furthermore, the method represents high selectivity for NO and shows a fast (within 5 min) and specific fluorescence response toward NO with a linear range from 0.25 to 2.0 μM; the strategy has a limit of detection (LOD) of  0.15 μM. More importantly, the probe was successfully used to detect NO in cell lysate. The recovery was between 98.5 and 103.6%, and the relative standard deviation was between 0.4 and 1.8%. The endogenous NO in cells was successfully detected under the stimulation of L-arginine, which proved the possibility of the probe in real-time and rapid sensing in actual samples and cells. The results indicate that this sensing strategy has the potential to detect NO in the internal environment. Schematic of fluorescence detection of NO.

Biosorption Study of Methylene Blue (MB) and Brilliant Red Remazol (BRR) by Coconut Dregs

Water pollution has become a major issue in many countries, including Malaysia. Malaysia is one of the countries that suffers from this detrimental influence on water resource sustainability. Adsorption has been discovered to be a cost-effective and efficient method of removing contaminants such as pigments, dyes, and metal impurities. Many biomass-based adsorbent materials have been successfully used for the removal of dyes from aqueous solutions. In this study, the potential use of coconut dregs as the new biosorbent for the removal of Methylene Blue (MB) (basic dye) and Brilliant Red Remazol (BRR) (acidic dye) was investigated. The effects of adsorption time, adsorbent dosage, pH, and initial dye concentration on coconut dregs adsorption for MB and BRR dye were investigated using 2-Level Factorial Design of Design-Expert 7.1.5. The results indicated that the amount of dye adsorbed on the coconut dregs increased with increasing dye concentration, adsorbent dosage, and adsorption time. However, both MB and BRR dyes favor different pH for the adsorption process. The adsorption capacity of MB dye increased with increasing pH, while the adsorption capacity of BRR dye increased with decreasing pH. Removal of MB was optimum at pH 11, contact time of 240 min, a dosage of 0.25 g adsorbent, and an initial dye concentration of 50 mg/L. Meanwhile, for BRR dye, the optimum condition was pH 2, contact time of 180 min, the dosage of 0.25 g adsorbent, and an initial dye concentration of 50 mg/L. The equilibrium data for both dyes fitted very well with the Langmuir Isotherm equation giving a maximum monolayer adsorption capacity as high as 5.7208 mg/g and 3.7636 mg/g for Methylene Blue Dye and Brilliant Red Remazol dye, respectively. This study shows that coconut dregs can be one of the potential and low-cost biosorbents for the treatment of industrial dyes soon.

Mid-infrared optical switches enabled by metal-organic frameworks for compact high-power nanosecond laser sources at 3 µm

Pulsed lasers operating in the mid-infrared are of great importance for numerous applications in spectroscopy, medical surgery, laser processing, and communications. In spite of recent advances with mid-infrared gain platforms, the lack of a capable pulse generation mechanism hinders the development of compact mid-infrared pulsed laser source. Here we show that MIL-68(Al) and MIL-68(Fe), which are aluminum- and iron- based metal-organic frameworks (MOFs) with ordered atoms distribution and periodic mesoporous structure, constitute exceptional optical switches for the mid-infrared. We fabricated the MIL-68(Al) and MIL-68(Fe) via hydrothermal method and prepared reflection-type MIL-68(Al)- and MIL-68(Fe)- saturable absorber mirrors (SAMs). By employing the as-prepared SAMs in the laser cavities, we achieved high-power nanosecond Q-switched fiber lasers at 2.8 µm. Especially, the average output power and pulse duration of the MIL-68(Al) Q-switched fiber laser reached 809.1 mW and 567 ns, respectively. To the best of our knowledge, this is the first time to demonstrate that MIL-68(M) can be efficient optical switches for 3-µm mid-IR laser pulses generation. Our findings reveal that MIL-68(M) is promising saturable absorber for compact and high-performance mid-infrared pulsed lasers.

Rapid and Efficient Removal of Anionic Dye in Water Using a Chitosan-Coated Iron Oxide-Immobilized Polyvinylidene Fluoride Membrane

Anionic dyes are one of the most serious contaminants in water as these molecules are known to be toxic to many living organisms. Herein, we report the development of functionalized polyvinylidene fluoride membranes modified with chitosan-coated iron oxide nanomaterials (Fe-PVDF) for the efficient treatment of anionic dye-contaminated water. Aqueous solutions of anionic dyes could be captured rapidly by passing through the functionalized membrane under reduced pressure. Under neutral conditions, Fe-PVDF showed a maximum removal capacity of 74.6 mg/g for Evans blue (EB) through the adsorption process. In addition, the adsorption capacity was significantly enhanced up to 434.78 mg/g under acidic conditions. The adsorption process for EB matched well with the Langmuir model, indicating monolayer adsorption of the dye to the membrane surface. Moreover, Fe-PVDF can be reusable by a simple washing step in an alkaline solution, and thus, the composite membrane was applied several times without a significant decrease in its adsorption performance. The same composite membrane was further applied to the removal of five other different anionic dyes with high efficiencies. The adsorption mechanism can be explained by the electrostatic interaction between the positively charged chitosan and the negatively charged dye as well as the affinity of the sulfate groups in dye molecules for the surface of the iron oxide nanoparticles. The easy preparation and rapid decolorization procedures make this composite membrane suitable for efficient water treatment.

Recent Advances in MOF-Based Adsorbents for Dye Removal from the Aquatic Environment

The adsorptive removal of dyes from industrial wastewater using commercially available adsorbents is not significantly efficient. Metal–organic frameworks (MOFs) offer outstanding properties which can boost the separation performance over current commercial adsorbents and hence, these materials represent a milestone in improving treatment methods for dye removal from water. Accordingly, in this paper, the recent studies in the modification of MOF structures in dye removal from the aquatic environment have been discussed. This study aims to elaborate on the synthetic strategies applied to improve the adsorption efficiency and to discuss the major adsorption mechanisms as well as the most influential parameters in the adsorptive removal of dyes using MOFs. More particularly, the advanced separation performance of MOF-based adsorbents will be comprehensively explained. The introduction of various functional groups and nanomaterials, such as amine functional groups, magnetic nanoparticles, and carbon-based materials such as graphene oxide and CNT, onto the MOFs can alter the removal efficiency of MOF-based adsorbents through enhancing the water stability, dispersion in water, interactions between the MOF structure and the contaminant, and the adsorption capacity. Finally, we summarize the challenges experienced by MOF-based materials for dye removal from water and propose future research outlooks to be considered.

State of the art on the ultrasonic-assisted removal of environmental pollutants using metal-organic frameworks

The environmental and health issues of drinking water and effluents released into nature are among the major area of contention in the past few decades. With the growth of ultrasound-based approaches in water and wastewater treatment, promising materials have also been considered to employ their advantages. Metal-organic frameworks (MOFs) are among the porous materials that have received great attention from researchers in recent years. Features such as high porosity, large specific surface area, electronic properties like semi-conductivity, and the capacity to coordinate with the organic matter have resulted in a substantial increase in scientific researches. This work deals with a comprehensive review of the application of MOFs for ultrasonic-assisted pollutant removal from wastewater. In this regard, after considering features and synthesis methods of MOFs, the mechanisms of several ultrasound-based approaches including sonocatalysis, sonophotocatalysis, and sono-adsorption are well assessed for removal of different organic compounds by MOFs. These methods are compared with some other water treatment processes with the application of MOFs in the absence of ultrasound. Also, the main concern about MOFs including environmental hazards and water stability is fully discussed and some techniques are proposed to reduce hazardous effects of MOFs and improve stability in humid/aqueous environments. Economic aspects for the preparation of MOFs are evaluated and cost estimates for ultrasonic-assisted AOP approaches were provided. Finally, the future outlooks and the new frontiers of ultrasonic-assisted methods with the help of MOFs in global environmental pollutant removal are presented.

Adsorptive decontamination of doxycycline hydrochloride via Prosopis juliflora activated carbon: Parameter optimization and disposal study

This study deals with the removal of doxycycline hydrochloride (DOX) antibiotic, from aqueous environment by using Prosopis juliflora activated carbon (PJAC). PJAC was synthesized by chemical activation and pyrolysis of Prosopis juliflora. It was characterized by employing Fourier transform infrared spectroscopy (FTIR), scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX), X-ray diffraction analysis (XRD), and Brunauer-Emmett-Teller (BET) techniques. The specific surface area, pore volume, and pore diameter were evaluated as 320.45 m² /g, 0.176 cm³ /g, and 2.65 nm, respectively. Different functional groups (O-H, C-O, C=C, C-N, and C-C) present on PJAC promoted the adsorption of DOX. The influence of various adsorption parameters suggested by central composite design (CCD) model was determined using response surface methodology (RSM), and interactive effects of these were optimized. The thermodynamic and kinetic studies performed at optimized conditions, exhibited that adsorption was spontaneous and endothermic. The experimental data were well described with Langmuir, Redlich-Peterson, and Freundlich isotherm models while kinetics data were well described by pseudo second order. The excellent interactions between the PJAC and DOX resulted maximum adsorption capacity as 57.11 mg/g. The adsorption mechanisms was dominated by π - π interactions and hydrogen bonding. Moreover, almost complete encapsulation of DOX was achieved by stabilization of exhausted PJAC. PRACTITIONER POINTS: A wild harmful plant Prosopis juliflora was used to synthesize a low-cost and eco-friendly bio-sorbent PJAC. Adsorptive ability of PJAC was quantified for adsorption of DOX antibiotic from its aqueous solution. DOX uptake on PJAC was mainly governed by л-л EDA interactions and hydrogen bonding.

Fabrication of Stable MIL-53(Al) for Excellent Removal of Rhodamine B

Adsorptive purification of organic dyes in wastewater is significant to protect the water environment. Herein, MIL-53(Al) was successfully fabricated through a facile and versatile solvothermal strategy. The stability of MIL-53(Al) under high temperature, acid, base, and peroxide conditions was investigated. The porous MIL-53(Al) had high chemical stability, and the thermal stability reached up to 500 °C, which provided a good foundation for dye removal. MIL-53(Al) showed excellent adsorption performance. The maximum adsorption capacity of MIL-53(Al) for rhodamine B (RhB) can reach 1547 mg g^-1 under 303 K, and the corresponding removal efficiency exceeded 90% at the equilibrium time (120 min). The Langmuir model and pseudo-second-order model can well fit RhB adsorption on MIL-53(Al). Thermodynamic study and activation energy values over the range of 298-323 K revealed that the adsorption of RhB was a spontaneous and endothermic physical process in nature. The batch experimental results, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy analyses suggested that the hydrogen bonding and electrostatic interactions between the hydroxyl/carboxyl groups of MIL-53(Al) and RhB were the primary adsorption mechanisms. Besides, MIL-53(Al) had a higher selectivity to RhB than the coexisting ions in aqueous solution and a superior adsorption performance after five cycles.

From Microurchins to V2O5 Nanowalls: Improved Synthesis through Vanadium Powder and Fast, Selective Adsorption of Methylene Blue

Research on synthesizing micro- and nanosized materials directly from metals has attracted considerable attention because of its simplicity, ability to synthesize in large quantities, and high uniformity. This study proposes a simple method to synthesize high-uniformity or high-density V₂O₅ microurchins and nanowalls directly from vanadium powder. Remarkably, the synthesis condition of 60 °C for 1 h is considered to be an optimal condition to convert metals into micro- or nano-oxides. The as-synthesized V₂O₅ nanowalls can adsorb nearly 90% of methylene blue in the dark in 3 min. The adsorption selectivity of these samples with several pigments is investigated.

Engineering of appropriate pore size combined with sulfonic functionalization in a Zr-MOF with reo topology for the ultra-high removal of cationic malachite green dye from an aqueous medium

A Zr-based metal–organic framework with reo topology, denoted as Reo-MOF-1, was fabricated through a solvothermal method capable of efficiently removing the cationic MG dye from an aqueous medium.

Modern Carbon-Based Materials for Adsorptive Removal of Organic and Inorganic Pollutants from Water and Wastewater

Currently, a serious threat for living organisms and human life in particular, is water contamination with persistent organic and inorganic pollutants. To date, several techniques have been adopted to remove/treat organics and toxic contaminants. Adsorption is one of the most effective and economical methods for this purpose. Generally, porous materials are considered as appropriate adsorbents for water purification. Conventional adsorbents such as activated carbons have a limited possibility of surface modification (texture and functionality), and their adsorption capacity is difficult to control. Therefore, despite the significant progress achieved in the development of the systems for water remediation, there is still a need for novel adsorptive materials with tunable functional characteristics. This review addresses the new trends in the development of new adsorbent materials. Herein, modern carbon-based materials, such as graphene, oxidized carbon, carbon nanotubes, biomass-derived carbonaceous matrices-biochars as well as their composites with metal-organic frameworks (MOFs) and MOF-derived highly-ordered carbons are considered as advanced adsorbents for removal of hazardous organics from drinking water, process water, and leachate. The review is focused on the preparation and modification of these next-generation carbon-based adsorbents and analysis of their adsorption performance including possible adsorption mechanisms. Simultaneously, some weak points of modern carbon-based adsorbents are analyzed as well as the routes to conquer them. For instance, for removal of large quantities of pollutants, the combination of adsorption and other methods, like sedimentation may be recommended. A number of efficient strategies for further enhancing the adsorption performance of the carbon-based adsorbents, in particular, integrating approaches and further rational functionalization, including composing these adsorbents (of two or even three types) can be recommended. The cost reduction and efficient regeneration must also be in the focus of future research endeavors. The targeted optimization of the discussed carbon-based adsorbents associated with detailed studies of the adsorption process, especially, for multicomponent adsorbate solution, will pave a bright avenue for efficient water remediation.

Investigating Methylene Blue Removal from Aqueous Solution by Cysteine-Functionalized Mesoporous Silica

In this study, mesoporous silica nanoparticles (MSNs) were synthesised using the Stober method and functionalised with cysteine (MSN-Cys) for removal of Methylene Blue (MB) from aqueous solution using the batch method. The adsorbent nanoparticles were characterised by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), FTIR, BET, and TGA. Several influential factors on the adsorption of MB onto the surface of MSN-Cys particles were investigated, including pH, initial concentration, and contact time. The adsorption capacity of MB from aqueous solution increased from circa 70 mg/g MSN-Cys in acidic media to circa 140 mg/g MSN-Cys in basic media. Adsorption isotherms and kinetic models of adsorption were used to clarify the adsorption process. The measured adsorption isotherm was fitted with a Freundlich model for all solutions, and the kinetic model was determined to be pseudo-second-order.

Porous 3,4-di(3,5-dicarboxyphenyl)phthalate-based Cd2+ coordination polymer and its potential applications

Porous coordination polymers with organic aminium as one of the guest species possess a potential application in dye adsorption and white-light material manufacture. Polycarboxylic acid with multiple COOH substituents tends to form this type of porous material (with metal ion). Here the solvothermal self-assembly between Cd²⁺ and a hexacarboxylic acid creates such a porous material [(CH₃)₂NH₂]₆[Cd₃(L)₂]·5DMF·3H₂O (H₆L = 3,4-di(3,5-dicarboxyphenyl)phthalic acid) 1. Total potential guest accessible void volume in 3-D 1 is found to be 4327 Å³. Based on its better porous structure and stability, the ability of 1 to adsorb organic dyes is investigated. It has been proved that (i) 1 can selectively adsorb cationic dyes as Azure A (AA⁺) and/or Methylene Blue (MB⁺), rather than neutral and anionic ones; (ii) the maximum adsorption capacity is 698.2 mg·g^-1 for AA⁺ and 573.2 mg·g^-1 for MB⁺, respectively; and (iii) to the adsorption of AA⁺, it can be recycled for at least five rounds. Also, it is utilized to fabricate the while-light emitting material. Based on the blue-light emission of 1, the trace Eu³⁺ and Tb³⁺ ions are introduced into the pores of 1 successfully, obtaining a white-light emitting material Eu³⁺/Tb³⁺@1 (CIE chromaticity coordinates: (0.33, 0.32)). Meanwhile, Eu³⁺/Tb³⁺@1 is found to be a potential fluorescence photochromic material, showing a yellow-white-blue light emission. According to these investigations, the relationship between material structure and its adsorption property for dyes, the points that should be paid attention to in the construction of white-light emitting materials as well as the potential adsorption mechanism for dyes and rare earth ions are deeply discussed.

Fluorescence determination of quercetin in food samples using polyhedron-shaped MOF@MOF(NUZ-8) based on NH2-UiO-66 and ZIF-8

A new metal-organic framework compound (MOF@MOF, NUZ-8) comprised of NH₂-UiO-66 and ZIF-8 under the polyvinylpyrrolidone (PVP) as the structure modifier was synthesized through an internal extended growth method (IEGM). The resulting NUZ-8 emerged the unreported unique polyhedron shape and showed considerable specific surface area (1466.1862 m²/g), excellent adsorption capacity, and fluorescence. NUZ-8 was used as a probe for the rapid optical detection of natural antioxidant quercetin (QCT). Its outstanding selectivity and sensitivity to QCT are derived from the fact that NH₂-UiO-66 acted as an optical tentacle to perceive QCT in virtue of its luminescence advantages, and ZIF-8 realized the selective enrichment of the QCT through its electron-rich framework structure. The experiments were carried out at an excitation wavelength of 335 nm and an emission wavelength range of 370-530 nm. Under conditions of the investigation, this probe realized the rapid detection of QCT and considerable adsorption capacity with wide linearity (0.3-80 μM), a low detection limit (0.14 μM), and acceptable recoveries (84.0-97.0%) in red wine samples, properties which were superior to many other detection platforms. The synthesis and the use of the above polyhedral composite provide guidance for the application of the IEGM in enhancing chemical sensing and instant determination of drugs.Graphical abstract Flow chart of this paper.

Fabrication of a Smartphone-Based Spectrophotometer and Its Application in Monitoring Concentrations of Organic Dyes

In this study, an in-house constructed paper-based spectrophotometer is presented and demonstrated for detecting three organic dyes, namely, methylene blue, malachite green, and rhodamine B, and monitoring the efficiency of their removal from a wastewater sample with Sistan sand as a costless adsorbent. The compact design and light weight of this simple spectrophotometer delivered portability, with materials costing less than a dollar. Spectral analysis of the captured images was performed using free downloadable software from the Google Play store. The main experimental parameters affecting the efficiency of dye adsorption including pH, sorbent dosage, initial dye concentration, and contact time were investigated and optimized using the Taguchi design experimental method. Validation experiments were performed using a standard commercial bench-top spectrophotometer, and results were compared in terms of analytical performance, speed, and cost of analysis. The smartphone-based spectrometer was able to measure accurately, as confirmed using the commercial spectrometer, with enhanced sensitivity for methylene blue and rhodamine B. The combination of the high spectral accuracy of the paper-based spectrophotometer, together with sand as a readily accessible sorbent, enabled us to develop a powerful yet simple approach and tool for the removal and monitoring of dyes within wastewater samples, which is potentially available to everybody who owns a smartphone.

UiO-66(Ti)-Fe3O4-WO3 photocatalyst for efficient ammonia degradation from wastewater into continuous flow-loop thin film slurry flat-plate photoreactor

This work presents the characterization of novel synthesized UiO-66(Ti)-Fe₃O₄-WO₃ magnetic photocatalyst and investigates their photocatalytic activity for the photodegradation of ammonia in a designed continuous flow-loop thin-film slurry flat-plate photoreactor (TFSR). Excellent ammonia degradation efficiency was achieved in the presence of the synthesized catalyst at ambient conditions using no more reactive oxidant species. Several independent variables involving catalyst mass, flowrate, pH, irradiation time and initial ammonia concentration as well as corresponding experiments were analyzed and design using the central composite design (CCD). The influence and significance of each parameter and their binary interactions were then evaluated by applying the analysis of variance. The ammonia degradation efficiency of 91.80 % with the desirability of 0.903 were obtained at optimum values of operational parameters including 550 mL/min,10, 0.125 g/L, 60 min and 30 mg/L for solution flowrate, pH, catalyst mass, irradiation time and initial ammonia concentration, respectively. Furthermore, the liquid phase products of ammonia degradation such as nitrate and nitrite ions were completely removed, and purified water was produced using the combination of reverse osmosis process and mixed resins beds. The photocatalyst mechanism study revealed that [Formula: see text] was the predominant reactive oxygen species in the ammonia photodegradation.

Modeling azo dye removal by sono-fenton processes using response surface methodology and artificial neural network approaches

Textile industry wastewaters, which cause serious problems in the environment and human health, include synthetic dyes, complex organic pollutants, surfactants, and other toxic chemicals and therefore must be removed by advanced treatment methods. Determination of appropriate treatment conditions for efficient use of advanced treatment methods is an important and necessary step. In the last thirty years, the Artificial Neural Network-Genetic Algorithm (ANN-GA) and Response Surface Methodology (RSM) have emerged as the most effective empirical modeling and optimization methods especially for nonlinear systems. Reactive Red 195 azo dyestuff was chosen as the target pollutant. The color removal efficiency was modeled and optimized as a function of Sono-Fenton conditions such as H₂O₂ dosage, Fe²⁺ dosage, initial pH value, ultrasound power, and ultrasound frequency, using ANN-GA and RSM. The generalization and predictive ability of these methods were compared using the results of the 46 experimental sets generated by the Box-Behnken design. The mean square errors for these models are 3.01612 and 0.00295, and the regression coefficients showing the superiority of ANN in determining nonlinear behavior are 0.9856 and 0.9164, respectively. In optimal conditions, the prediction errors with hybrid ANN-GA and RSM models are 0.002% and 3.225%, respectively.

Nanosheets of MIL-53(Al) applied in membranes with improved CO2/N2 and CO2/CH4 selectivities

Nanosheets obtained from MOF MIL-53(Al) applied in mixed matrix membranes with improved CO₂/N₂ and CO₂/CH₄ selectivities.

Silver-choline chloride modified graphene oxide: Novel nano-bioelectrochemical sensor for celecoxib detection and CCD-RSM model

In this study, silver nanoparticles modified choline chloride functionalized graphene oxide (AgNPs-ChCl-GO) was synthesized using sonochemical method and utilized as a bioelectrochemical sensor for detection of celecoxib (CEL). The characterization studies were ultimately performed in order to acheive a more complete understanding of the morphological and structural features of the AgNPs-ChCl-GO using different techniques including FT-IR, AFM, FE-SEM, EDX, and XRD. AgNPs-ChCl-GO demonstrated a significant improvement in the reduction activity of CEL due to the enhancement in the current response compared to the bare carbon paste electrode (CPE). The optimum experimental conditions, were optimized using central composite design (CCD) methodology. The differential pulse voltammetry (DPVs) showed an expanded linear dynamic ranges of 9.6 × 10^-9-7.4 × 10^-7 M for celecoxib in Britton-Robinson buffer in pH 5.0 with. LOD (S/N = 3) and LOQ (S/N = 10) were obtained 2.51 × 10^-9 M and 6.58 × 10^-9 M respectively. AgNPs-ChCl-GO-carbon paste electrode exhibited suitable properties and high accuracy determination of celecoxib in the human plasma sample.