High-efficient removal of organic dyes from model wastewater using Mg(OH)2-MnO2 nanocomposite: Synergistic effects of adsorption, precipitation, and photodegradation

Retrieval of Cu2+ and Cd2+ ions from aqueous solutions using sustainable guar gum/PVA/montmorillonite nanocomposite films: effect of temperature and adsorption isotherms

Uncontrolled or improperly managed wastewater is considered toxic and dangerous to plants, animals, and people, as well as negatively impacting the ecosystem. In this research, the use of we aimed to prepare polymer nanocomposites (guar gum/polyvinyl alcohol, and nano-montmorillonite clay) for eliminating heavy metals from water-based systems, especially Cu2+ and Cd2+ ions. The synthesis of nanocomposites was done by the green method with different ratios of guar gum to PVA (50/50), (60/40), and (80/20) wt%, in addition to glycerol that acts as a cross-linker. Fourier-transform infrared spectroscopy (FT-IR) analysis of the prepared (guar gum/PVA/MMT) polymeric nano-composites' structure and morphology revealed the presence of both guar gum and PVA's functional groups in the polymeric network matrix. Transmission electron microscopy (TEM) analysis was also performed, which verified the creation of a nanocomposite. Furthermore, theromgravimetric analysis (TGA) demonstrated the biocomposites' excellent thermal properties. For those metal ions, the extreme uptake was found at pH 6.0 in each instance. The Equilibrium uptake capacities of the three prepared nanocomposites were achieved within 240 min. The maximal capacities were found to be 95, 89 and 84 mg/g for Cu2+, and for Cd2+ were found to be 100, 91, 87 mg/g for guar gum (80/20, 60/40 and 50/50), respectively. The pseudo-2nd-order model with R2 > 0.98 was demonstrated to be followed by the adsorption reaction, according to the presented results. In less than 4 hours, the adsorption equilibrium was reached. Furthermore, a 1% EDTA solution could be used to revitalize the metal-ion-loaded nanocomposites for several cycles. The most promising nanocomposite with efficiency above 90% for the removal of Cu2+ and Cd2+ ions from wastewater was found to have a guar (80/20) weight percentage, according to the results obtained.

Highly efficient and selective removal of anionic dyes from aqueous solutions using polyacrylamide/peach gum polysaccharide/attapulgite composite hydrogels with positively charged hybrid network

To avoid the weakness (lower adsorption rate and selectivity) of peach gum polysaccharide (PGP) and improve the adsorption performance of polyacrylamide (PAAm) hydrogel (lower adsorption capacity), in the present work, the PGP was chemically tailored to afford ammoniated PGP (APGP) and quaternized PGP (QPGP), and attapulgite (ATP) was bi-functionalized with cation groups and carbon‑carbon double bond. Then, PAAm/APGP and PAAm/QPGP/ATP hydrogels were synthesized via redox polymerization. The synthesis procedure and properties of hydrogels were traced by FTIR, SEM, XPS, TGA, TEM, and BET methods, and the dye adsorption performance of the hydrogels was evaluated using the new coccine (NC) and tartrazine (TTZ) aqueous solutions as the model anionic dyes. Effects of initial dye concentration, pH, and ionic strength on the adsorption were investigated. Compared with PAAm/APGP hydrogel, PAAm/APGP/ATP hydrogel exhibits higher adsorption rate, superior adsorption capacity, stability, and selectivity towards anionic dye. The adsorption process of PAAm/QPGP/ATP hydrogel reached equilibrium in about 20 min and followed the pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacities towards NC and TTZ of PAAm/QPGP/ATP hydrogel were calculated as 873.235 and 731.432 mg/g. This hydrogel adsorbent originating from PAAm, PGP, and ATP shows great promise for application in practical water treatment.

A magnetically recyclable carboxyl-functionalized chitosan composite for efficiently removing methyl orange from wastewater: Isotherm, kinetics, thermodynamic, and adsorption mechanism

In this study, a kind of magnetically recyclable adsorbent for dyes was synthesized by grafting diethylenetriamine pentaacetate acid (DTPA) to the composite of Fe3O4 microspheres and crosslinked chitosan (CS). The microstructures, molecular structure, crystal structure, and magnetic hysteresis loops of the chitosan matrix adsorbent before and after grafting was characterized. The results suggested that DTPA was covalent bonded with the composite of Fe3O4 microspheres and chitosan. The modified composite has larger specific surface area and can realize rapid solid-liquid separation. Batch experiments were conducted to optimize the parameters affecting the adsorption of methyl orange (MO). The adsorption process could be better described by pseudo-second-order kinetics model and Langmuir isotherm equation, and its saturated adsorption capacity of the modified adsorbents was 1541.5 mg·g-1 at 25 °C, which was 1.40 times of that the unmodified adsorbent (1104.1 mg·g-1). The obtained values of the thermodynamic parameters indicated that the adsorption was a spontaneous process. The regeneration experiment proved the stability and reproducibility of the adsorbent even after five cycles of adsorption-desorption. The primary adsorption mechanism was electrostatic interaction and hydrogen bonding. The adsorbent could be potentially applied for removing dyes from wastewater in wide pH of range, especially acid wastewater.

Hydrogel Nanocomposite Towards Optical Sensing of Spermine in Biomedical and Real-Life Food Samples and Remediation of Toxic Dyes from Wastewater

Nanocomposites such as graphene oxide (GO) have been incorporated into hydrogels to enhance conventional hydrogels' properties and develop new functions. Unique and strong molecular interactions between GO and low molecular weight gelators allow the fabrication of various functional hydrogels suitable for different applications. In the present study, we report a stable and soft nanocomposite hydrogel comprising a pyrene-based chiral amphipath having an amino acid (l-phenylalanine) core with pendant oligo-oxyethylene hydrophilic chains and GO. The mechanical and viscoelastic properties of the nanocomposite hydrogel were thoroughly studied using various spectroscopic, microscopic, and mechanical techniques. Even without GO, native hydrogels could form a self-supported thermoreversible and thixotropic hydrogel composed of the fibrillar network. Unlike native hydrogels, the morphological investigation of nanocomposite gels shows the presence of cross-linked nanosheet-like structures. The combined effect of π-π stacking and H-bonding interactions is the driving force for the formation of such composite hydrogels. Moreover, the nanocomposite hydrogels possess significantly superior mechanical stiffness than the native hydrogels. Interestingly, the thixotropic properties observed with the parent gel were retained even in the presence of carbon nanomaterials (GO). The nanocomposite hydrogel could be employed in the optical sensing of a biogenic polyamine, spermine, resulting in a visible gel-to-sol transition. The superior electrostatic interaction between the GOs and spermine molecules might have led to the release of entrapped fluorogenic dyes from the hydrogel network and a turn-on emission response. The sensory system was employed to analyze spermine content in human urine samples and decomposed food items. A gel-coated paper strip was also developed for onsite detection of the spermine. The nanocomposite hydrogel was further utilized to remove toxic organic dyes such as methylene blue (MB) and rhodamine B (RhB) from the aqueous media. The nanocomposite hydrogel thus showed excellent dye removal capabilities and was also found to be recyclable. Calculations of different mechanical parameters suggest that the dye removal efficiency of the nanocomposite hydrogel was better for MB than for RhB.

Competitive and cooperative adsorption analysis for dye removal from multicomponent system using Prosopis juliflora activated carbon

In this study, performance evaluation of two adsorbents synthesized using invasive weed, i.e., Prosopis juliflora, was chemically activated using hydrochloric acid (HPJ) and sodium hydroxide (NPJ). The synthesized adsorbents HPJ and NPJ were subjected to SEM, EDX, XRD, FTIR, and porosimetry analysis for characterization and applied for adsorptive removal of rhodamine B (RB) and methyl orange (MO) dyes from monocomponent (MO/RB) and multicomponent (MO + RB) systems in batch mode. Meanwhile, the effect of operational parameters such as contact time, HPJ and NPJ dosage, MO/RB concentration, and [Formula: see text] on sorption of MO/RB dyes was investigated. The adsorption data was modeled through various kinetic and equilibrium models. On the other hand, the multi-dye sorption system was modeled using Langmuir competitive isotherm. Furthermore, the effect of presence of one dye on sorption of other and vice versa, i.e., competitive (antagonistic) and cooperative (synergistic) nature of sorption process, was investigated. From the results, it was observed that pseudo-second-order kinetic and Langmuir isotherm models best fit the adsorption kinetic and equilibrium data for sorption of MO and RB dyes using both HPJ and NPJ as adsorbents. Langmuir's maximum sorption ability (qm) of HPJ for sorption of MO and RB dyes was observed to be 12.77 mg/g and 9.95 mg/g, respectively, from the monocomponent system. On the other hand, qm of NPJ for sorption of MO and RB dyes was observed to be 10.51 mg/g and 8.69 mg/g, respectively. Langmuir's sorption ability (qm) was slightly higher in the MO + RB mixture in contrast to MO/RB. As a result, the sorption of MO/RB dyes from the MO + RB system showed synergistic nature. In conclusion, the HPJ and NPJ could be effectively used as sorbents for sorption of dyes from effluents.

Methylene blue removal from aqueous solutions using a biochar/gellan gum hydrogel composite: Effect of agitation mode on sorption kinetics

Hydrogel membranes are prepared by casting a mixture of gellan gum (associated with PVA) and biochar produced from a local Egyptian plant. The mesoporous material is characterized by a specific surface area close to 134 m² g^-1, a residue of 28 % (at 800 °C), and a pH_PZC close to 6.43. After grinding, the material is tested for Methylene Blue sorption at pH 10.5: sorption capacity reaches 1.70 mmol MB g^-1 (synergistic effect of the precursors). The sorption isotherms are fitted by both Langmuir and Sips eqs. MB sorption increases with temperature: the sorption is endothermic (∆H°: 12.9 kJ mol^-1), with positive entropy (∆S°: 125 J mol^-1 K^-1). Uptake kinetics are controlled by agitation speed (optimum ≈200 rpm) and resistance to intraparticle diffusion. The profiles are strongly affected by the mode of agitation: the equilibrium time (≈180 min) is reduced to 20-30 min under sonication (especially at frequency: 80 kHz). The mode of agitation controls the best fitting equation: pseudo-first order rate agitation for mechanical agitation contrary to pseudo-second order rate under sonication. The sorption of MB is poorly affected by ionic strength (loss <6 % in 45 g L^-1 NaCl solution). Desorption (faster than sorption) is completely achieved using 0.7 M HCl solution. At the sixth recycling, the loss in sorption is close to 5 % (≈ decrease in desorption efficiency). The process is successfully applied for the treatment of MB-spiked industrial solution: the color index decreases by >97 % with a sorbent dose close to 1 g L^-1; a higher dose is required for maximum reduction of the COD (60 % at 3 g L^-1).

Efficient Removal of Congo Red, Methylene Blue and Pb(II) by Hydrochar-MgAlLDH Nanocomposite: Synthesis, Performance and Mechanism

Organic dyes and heavy metals often coexist in industrial effluents, and their simultaneous removal is a grand challenge. Herein, a hydrochar and MgAl layered double hydroxide (HC-MgAlLDH) nanocomposite was prepared via a facile one-step hydrothermal route, and applied to remove anionic Congo red (CR), cationic Methylene blue (MB) and Pb(II) from aqueous solutions. The nanocomposite was formed by interweaving amorphous HC and crystalline MgAlLDH nanoplates and possessed more functional groups, lower zeta potential and larger specific surface area than uncomposited MgAlLDH. Batch removal experiments showed that the components HC and LDH dominated the CR and MB removals, respectively, whereas Pb(II) removal was conjointly controlled by the two components. The maximum Langmuir removal capacities of the nanocomposite to sole CR, MB, or Pb(II) were 348.78, 256.54 or 33.55 mg/g. In binary and ternary systems, the removal capacities of CR and MB only slightly decreased, while the capacity of Pb(II) increased by 41.13-88.61%. The increase was related to the coordination of Pb(II) with the sulfur-containing groups in dyes and the precipitation of PbSO₄. Therefore, the simultaneous removal of CR, MB and Pb(II) was involved in a synergistic effect, including electrostatic adsorption, π-π interaction, coordination and precipitation. The present work shows that the HC-MgAlLDH nanocomposite has great potential for wastewater integrative treatment.

Facile synthesis of multifunctional C@Fe3O4-MoO3-rGO ternary composite and its versatile roles as sonoadsorbent to ameliorate triphenylmethane textile dye and as potential electrode for supercapacitor applications

The toxic wastewater effluents from textile dyes have been a significant environmental threat worldwide in recent decades. Against this backdrop, this study investigates the performance of C@Fe₃O₄-MoO₃-rGO as a sonoadsorbent to ameliorate crystal violet (CV) dye from the aqua matrix and further explores its potential as an electrode in supercapacitor applications. The phase purity, crystal structure, surface morphology, thermal stability and magnetic behaviour characteristics of the composite were studied using various characterisation techniques such as powder X-ray diffraction (XRD), Raman Spectroscopy, Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HRTEM), Thermogravimetric analysis (TGA) and Vibrating-sample magnetometry (VSM). From the Langmuir isotherm model, the synthesised sonoadsorbent exhibited a maximum adsorption capacity of 1664.26 mg/g for crystal violet, which is remarkably high. Further, to its inherited magnetic characteristics, the composite can be easily separated from the solution by using an external magnet. Furthermore, the working electrode was synthesised with 80% active material, 10% carbon black, and 10% polyvinylidene difluoride to investigate its suitability in supercapacitor applications. The C@Fe₃O₄-MoO₃-rGO composite exhibited an excellent capacitance value of 180.36 F/g with commendable cycling stability, making it suitable as a potential cathode material for the next generation supercapacitors.

Fe3O4-Mg(OH)2 nanocomposite as a scavenger for silver nanoparticles: Rational design, facile synthesis, and enhanced performance

Silver nanoparticles (AgNPs) are considered as emerging contaminants because of their high toxicity and increasing environmental impact. Removal of discharged AgNPs from water is crucial for mitigating the health and environmental risks. However, developing facile, economical, and environment-friendly approaches remains challenging. Herein, an Fe₃O₄-Mg(OH)₂ nanocomposite, as a novel magnetic scavenger for AgNPs, was prepared by loading Fe₃O₄ nanoparticles on Mg(OH)₂ nanoplates in a one-pot synthesis. Batch removal experiments revealed that the maximum removal capacities for the two model AgNPs (citrate- or polyvinylpyrrolidone-coated AgNPs) were 476 and 442 mg/g, respectively, corresponding to partition coefficients 8.03 and 4.89 mg/g/μM. Removal feasibilities over a wide pH range of 5-11 and in real water matrices and scavenger reusability with five cycles were also confirmed. Both Fe₃O₄ and Mg(OH)₂ components contributed to the removal; however, their nanocomposites exhibited an enhanced performance because of the high specific surface area and pore volume. Chemical adsorption and electrostatic attraction between the coatings on the AgNPs and the two components in the nanocomposite was considered to be responsible for the removal. Overall, the facile synthesis, convenient magnetic separation, and high removal performance highlight the great potential of the Fe₃O₄-Mg(OH)₂ nanocomposite for practical applications.

The Adsorptive Removal of Bengal Rose by Artichoke Leaves: Optimization by Full Factorials Design

Currently, the dye industry is increasing its production as a consequence of the growing need for their products in different manufacturing sectors, such as textiles, plastics, food, paper, etc... Thereafter, these industries generate very large volumes of effluents contaminated by these dyes, which require proper removal treatment before final discharge of the effluents into the environment. In this study, artichoke leaves were used as an economical and eco-friendly bio-adsorbent for Bengal Rose (BR) dye removal. Bio-adsorbent obtained from artichoke leaves was ground to powder size. The resulting powder was characterized by different methods, such as Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy(SEM), X-ray Diffraction (XRD), Fourier transfer infrared (FTIR), pH at point of zero charge (pHpzc), equilibrium pH, iodine number, methylene blue number, phenol number, density, Energy dispersive X-ray spectroscopy (EDX) and Thermo-gravimetric analysis (TGA). Thereafter, the bio-adsorbent was used to study its capability for removing BR dye by testing contact time, initial concentration of dye and temperature. The results show that the saturation of bio-sorbent was reached after 40 min and the removal rate of BR dye by artichoke leaves powder (ALP) was 4.07 mg/g, which corresponds to a removal efficiency of 80.1%. A design of experiences (DOE) based on a two-level full factorial design (23) was used to study the effects of different parameters, such as pH, temperature and bio-adsorbent dosage on BR dye removal efficiency. The obtained results show that the highest removal efficiency was 86.5% for the optimized values of pH (4), temperature (80 °C) and bio-adsorbent dosage (8 g/L). Furthermore, a satisfying accordance between experimental and predicted data was observed. The kinetic and isotherm studies show that the pseudo-second order model simulated adequately the obtained data and it was found that Langmuir and Temkin isotherm models are liable and suitable for evaluating the adsorption process performance. Free energy change of adsorption (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were furthermore calculated to predict the nature of the adsorption process.

Synthesis, Characterization, and Application of Magnetized Lanthanum (III)-Based Metal-Organic Framework for the Organic Dye Removal from Water

A hybrid composite based on metal-organic framework (MOF) was chemically fabricated by embedding the magnetic Fe3O4 nanoparticles within amino-functionalized porous La-MOF (MOF/NH2) to produce a highly efficient and reusable composite of MOF/NH2/Fe3O4. Different proper techniques were used for the characterization of surface morphology and chemical arrangement of the prepared MOF/NH2/Fe3O4 composite. The characterization results using various techniques including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer, Emmett, and Teller analysis (BET), and vibrating sample magnetometer (VSM) approved the successful fabrication of MOF with amino arms on its surface besides the well magnetization using magnetic nanoparticles. The MOF/NH2/Fe3O4 composite showed enhanced adsorption capacity (618 mg/g) toward methyl orange (MO) anionic dye which is higher than many commercial reported adsorbents due to the presence of many types of adsorption sites (NH2 groups and lanthanum sites), large surface area of MOF, and the synergetic effect of magnetic nanoparticles. Moreover, the MOF/NH2/Fe3O4 composite showed selective adsorption of MO dye from dye mixtures owing to the electrostatic attraction. Also, the MOF/NH2/Fe3O4 composite retained over 90% of its efficiency for the dye removal even after six successive cycles. So, the present study provided a practical strategy for the design of functional MOF hybrid composites. Furthermore, due to the adaptability of its architectural form, it is a potential adsorbent material for industrial wastewater treatment uses.

Review on some metal oxide nanoparticles as effective adsorbent in wastewater treatment

Water contamination has turned into one of the most serious issues in the world. Nanomaterials are proficient to carry away heavy metals, organic and inorganic dyes, pesticides, and small molecules from polluted water. In this regard, nanoparticles have gained much attention due to their extraordinary properties compared to bulk materials. Metal oxide nanoparticles and nanocomposites have several advantages such as elevated surface area, low concentration, easily separable after treatment and so on. Among many feasible techniques, the adsorption process is one of the most useful techniques for removing heavy ions and dyes from wastewater and has gained much attention from researchers. Several studies on metal oxide nanoparticles and their use in wastewater treatment have been published in the literature. This chapter gives an outline about five metal oxide based nanomaterials and nanocomposites as well as their applications in water pollution removal where the efficiency, limits and favourable circumstances are compared and explored. This article surely helps to gather information about some metal oxide nanoparticles and nanocomposites in wastewater treatment by the adsorption technique. In this review article, we primarily focused on five metal oxide nanoparticles and some of their recent applications published in the last two years.

Designing Z-scheme AgIO4 nanorod embedded with Bi2S3 nanoflakes for expeditious visible light photodegradation of congo red and rhodamine B

The present study describes the enhanced photodegradation of organic pollutant dyes, congo red (CR) and rhodamine B (RhB) dyes under visible light irradiation. AgIO₄ nanorods decorated on Bi₂S₃ nanoflakes in various proportions were synthesized via sono-chemical route wherein the deposition of varying amounts of AgIO₄ on Bi₂S₃ plays a pivotal role in improving the photodegradation ability. The characterization of the as-synthesized nanohybrids was assessed by XRD, UV-vis DRS, PL, EIS, ESR, FT-IR, XPS, HR-TEM, FE-SEM, N₂ adsorption and desorption techniques. The effect of initial CR and RhB dye concentration, reaction pH and usage of nanohybrid concentration were investigated where 30%-AgIO₄/Bi₂S₃ exhibited excellent visible light photodegradation of 95.58% for CR and 96.11% for RhB dyes at 140 min and 100 min respectively. The superoxide (•O^2-) and hydroxyl radicals (•OH) played predominant role in the photodegradation of CR and RhB which is experimentally confirmed by radical trapping experiments. Also, the photocatalysts exhibited good photo stability and excellent reusability. The TOC analysis confirmed the complete mineralization of CR and RhB dyes by the nanohybrid and the formation of possible intermediate and degradation pathway was delineated based on GC/MS analysis. The outstanding photodegradation performance were ascribed to the Z-scheme charge transfer path, which effectively promotes the separation and transfer of e^-/h⁺ pairs, resulting in a strong redox activity of the accumulated charge to decompose organic dyes during the degradation reaction. The study suggested that the nanohybrid can be utilized for the removal of organic pollutants from the contaminated water bodies.

Preparation of carboxymethyl cellulose/graphene composite aerogel beads and their adsorption for methylene blue

Carboxymethyl cellulose/ graphene composite aerogel beads (CMC/GAs) were prepared by the easily scaling-up method, i.e., wet spinning- environmental pressure drying method. The influences of the type and concentration of coagulating bath on the formation of aerogel beads were discussed, and the forming mechanism was analyzed. The CMC/GAs was characterized through SEM, XRD, FI-IR, Raman, XPS, electronic universal testing machine and other methods. The CMC/GAs-30 has an average particle size and a mean pore diameter of 3.83 mm and 82 μm, respectively. The analysis results indicated that the adsorption mechanisms of CMC/GAs on methylene blue (MB) are mainly through the electrostatic interaction. The adsorption process conforms to the Langmuir model (R² = 0.9964) and pseudo-second-order kinetic model (R² is higher than 0.99). When the particle size of CMC/GAs-30 decreases, the equilibrium adsorption capacity for MB increases. Under the experimental conditions explored, the Langmuir maximum adsorption capacity of CMC/GAs-30 for MB is 222.72 mg.g^-1. The CMC/GAs-30 show good recycle performance in MB adsorption. The removal rate of MB from water by CMC/GAs-30 remained at about 90% after 30-times adsorption- regeneration cycles.

Apple-like Zinc-Oxide Mesocrystals as Robust and Versatile Photocatalysts for Efficient Degradation of Eight Different Organic Dyes

The discovery of efficient photocatalysts is a promising key approach to solve the environmental crisis caused by hazardous organic dyes. Herein, we have for the first time created ZnO mesocrystals with a novel apple-like morphology. We have developed a one-pot biomineralization route to synthesize ZnO nanostructures at room temperature by using the rod-like protein collagen as the template. The shape of ZnO mesocrystals can be conveniently tuned from fusiform-like and kiwi-like to orange-like, apple-like, and snack-like structures. The apple-like ZnO mesocrystals show a significantly better photodegradation efficiency than the commercial ZnO powder as well as other nanostructured ZnO materials for both rhodamine B (RhB) and methyl orange (MO). Furthermore, the apple-like zinc-oxide mesocrystals can degrade all of the tested eight different types of organic dyes (RhB, rhodamine 6G, methylene blue, Coomassie brilliant blue R250, BPB, MO, Li Chunhong S, and carmine) simply under the exposure of sunlight, demonstrating their superior photodegradation prowess, environmental amiability, and energy-saving features. The novel robust and versatile photocatalyst has greatly advanced our abilities for the elimination of organic dyes. The green, one-pot strategy provides a convenient method for the construction of novel metal-oxide nanostructures with promising applications in environmental protection.