Evaluation of poly(ethylene diamine-trimesoyl chloride)-modified diatomite as efficient adsorbent for removal of rhodamine B from wastewater samples

New recyclable and functionalized chitosan-based polyurethane foams for effective and incessant removal of Orange II (OII) and Rhodamine B (RhB) dyes from water

The development of new efficient materials for the removal of water-soluble toxic organic dyes has been one of the focused research areas in the recent past. There is a strong demand for the new materials as most of the reported techniques/materials suffer from serious limitations. In this regard, a series of flexible chitosan-based task-specific polyurethane foams (PUCS-GP, PUCS-CA-GP, PUCS-TA-GP, and PUCS-GA-GP) associated with naturally available hydroxycarboxylic acids was developed. The basis for the preparation of these task-specific and functionalized PU foams is to possess amine groups for trapping the anionic dyes (example: Orange II denoted as OII) and carboxylic acid groups for attracting the cationic dyes (example: Rhodamine B denoted as RhB) under specified pH conditions. Batch adsorption experiments were conducted to assess and improve various parametric conditions. The experimental results revealed that the adsorption kinetics closely agree with the pseudo-second-order model having a maximum sorption capacity of 38.3 mg/g at pH 3 for OII on PUCS-GP and 48.4 mg/g at pH 6 for RhB on PUCS-CA-GP. Furthermore, the adsorption process was described by isotherms, kinetic equations and thermodynamic parameters (ΔG°, ΔH° and ΔS°). Notably, the regeneration of OII and RhB dyes from the exhausted PUCS-GP and PUCS-CA-GP materials was effectively accomplished. The recovered PUCS-GP shows >90 % OII and PUCS-CA-GP displays >70 % RhB removal efficiency even after twelve adsorption-desorption processes under mild conditions, demonstrating excellent recyclability/durability. The advantages of these functionalized foam materials are facile preparation, high adsorption capacity, good reusability, and very efficient removal of organic dyes from wastewater streams.

Enhanced photocatalytic degradation of Rhodamine B using gold nanoparticles decorated on BaTiO3 with surface plasmon resonance enhancement

This study focused on synthesizing and applying gold nanoparticle (Au NP) decorated barium titanate (BaTiO3) nanoparticles for photocatalytic purposes. BaTiO3 NPs were synthesized using a facile hydrothermal method. Various techniques were employed to characterize the structure and morphological characteristics of the prepared materials. The photocatalytic degradation of Rhodamine B over the Au NPs-modified BaTiO3 photocatalysts was studied. Trapping experiments were conducted using different scavengers to elucidate the degradation mechanism and the involvement of photogenerated species. The incorporation of an appropriate amount of Au NPs into the composites resulted in a significant improvement in photocatalytic activity, attributed to the combined effect of Schottky junction at the interface and the surface plasmon resonance of Au NPs.

Characterization of Chitosan-Hybridized Diatomite as Potential Delivery Systems of Oxaliplatin and 5-Fluorouracil Drugs: Equilibrium and Release Kinetics

The current work involves the modification of diatomite's biosiliceous frustules employing chitosan polymer chains (CS/Di) to serve as low-cost, biocompatible, multifunctional, and enhanced pharmaceutical delivery systems for 5-fluorouracil (5-Fu) together with oxaliplatin (OXPL). The CS/Di carrier displayed strong loading characteristics, notably at saturation (249.17 mg/g (OXPL) and 267.6 mg/g (5-Fu)), demonstrating a substantial 5-Fu affinity. The loading of the two types of medications onto CS/Di was conducted based on the kinetic behaviors of the conventional pseudo-first-order theory (R2 > 0.90). However, while the loading of OXPL follows the isotherm assumptions of the classic Langmuir model (R2 = 0.99), the loading of 5-Fu displays Fruendlich isotherm properties. Therefore, the 5-Fu loading displayed physical, heterogeneous, and multilayer loading properties, whereas the loading of OXPL occurred in homogeneous and monolayer form. The densities of occupied active sites of CS/Di were 37.19 and 32.8 mg/g for the sequestrations of OXPL and 5-Fu, respectively. Furthermore, by means of multimolecular processes, each loading site of CS/Di can bind up to 8 molecules of OXPL and 9 molecules of 5-Fu in a vertical orientation. This observation explains the higher loading capacities of 5-Fu in comparison to OXPL. The loading energies, which exhibit values <40 kJ/mol, provide confirmation of the dominant and significant consequences of physical processes as the regulating mechanisms. The release patterns of OXPL and 5-Fu demonstrate prolonged features over a duration of up to 120 h. The release kinetic simulation and diffusion exponents which are more than 0.45 provide evidence of the release of OXP and 5-Fu via non-Fickian transportation characteristics and the erosion/diffusion mechanism. The CS/Di carrier exhibited a substantial enhancement in the cytotoxicity of OXPL and 5-Fu against HCT-116 carcinoma cell lines, resulting in a reduction in cell viability by 4.61 and 2.26% respectively.

High biosorption of cationic dye onto a novel material based on paper mill sludge

The valorization of paper mill sludge (PMS) is the main goal of this study. The emissions of PMS continue to increase at global scale, especially from packaging paper and board sectors. The raw sludge was used to prepare an adsorbent to remove toxic pollutants from wastewater, the methylene blue (MB), an organic dye. Firstly, the physico-chemical characterization of PMS was done determining the crystalline phases of PMS fibers, the content of main elements, and the pH zero point charge, which was determined at around pH 7. The adsorption of MB on PMS powder was studied at 18 °C with an agitation of 200 rpm, being the best operating conditions 30 min of contact time, 250 mg L-1 of initial MB concentration and 0.05 g in 25 mL of adsorbent dose. Experimental data of MB adsorption was fitted to Langmuir and Freundlich isotherm equations. The Langmuir model was more accurate for the equilibrium data of MB adsorption at pH 5.1. The PFOM and PSOM were adjusted to experimental adsorption kinetics data, being PSOM, which describes better the MB adsorption by PMS powder. This was confirmed by calculating the maximum adsorption capacity with PSOM, which was 42.7 mg g-1, being nearly similar of the experimental value of 43.5 mg g-1. The analysis of adsorption thermodynamics showed that the MB was adsorbed exothermically with a ΔH0 = - 20.78 kJ mol-1, and spontaneously with ΔG0 from - 0.99 to - 6.38 kJ mol-1 in the range of temperature from 291 to 363 K, respectively. These results confirm that the sludge from paper industry can be used as biosorbent with remarkable adsorption capacity and low cost for the treatment of wastewater. PMS can be applied in the future for the depollution of the effluents from the textile industry, which are highly charged with dyes.

Novel silver-morphine-functionalized polypropylene (AgPP-mrp) nanocomposite for the degradation of dye removal by multivariate optimization approach

As a novel adsorbent, an opioid silver-morphine-functionalized polypropylene was synthesized through a one-pot reaction at room temperature and successfully used for the simple one-pot photocatalytic degradation catalyst of methyl orange removal from wastewater. UV spectral analysis reveals a special reference to the excitation of surface plasmon resonance as the main characteristic of the polymer-Ag nanocomposite in toluene solution peak at 420 nm in AgPP-mrp catalyst. The 1H NMR spectrum showed no sign of Ag NP peaks revealing small size distribution in the channels of morphine-functionalized polypropylene polymer. The morphology of silver nanoparticle-doped polymer through scanning electron microscopy (SEM-EDX) reveals PP-mrp with continuous matrix and Ag NPs (0.87 wt%). Furthermore, photocatalytic degradation of methyl orange was investigated on AgPP-mrp catalyst spectrophotometrically under solar irradiation in waste effluent, demonstrating high degradation efficiency. According to experimental findings, silver nanoparticles (AgPP-mrp) achieved high degradation capacities of 139 mg/g equivalent to 97.4% of photodegradation in a little period of time (35 min), as associated with previously stated materials and follow pseudo-second-order kinetic degradation tail of a high regression coefficient (R2 = 0.992). The suggested techniques offer a linear reaction for MO over the pH range of 1.5 to 5 and a degradation temperature of 25 to 60 °C. Central composite design and response surface methodology statistics recommend pH of the reaction medium and time as important variables for methyl orange degradation on AgPP-mrp photocatalytic. AgPP-mrp on the photocatalytic phenomenon based on heterojunction catalytic design producing electron holes (e-), as well as superoxides for the successful degradation of methyl orange.

Selective Removal of Boron from Aqueous Solutions Using ECH@NGM Aerogels with Excellent Hydrophilic and Mechanical Properties: Performance and Response Surface Methodology Analysis

The remediation of environmental boron contamination has received extensive research attention. The adsorbent ECH@NGM aerogel with high hydrophilic and mechanical properties was synthesized to remove boron. The ECH@NGM aerogel had a high adsorption capacity of 81.11 mg/g, which was 14.50% higher than that of commercial boron-selective resin Amberlite IRA743. The Freundlich model and pseudo-second-order model described the adsorption behavior well. In addition, the response surface methodology (RSM) could predict the experimental outcomes and optimize the reaction conditions, and X-ray photoelectron spectroscopy (XPS) and control tests were utilized to investigate probable adsorption mechanisms. These data showed that the B ← N coordination bond was the primary adsorption force. The adsorbent had good resistance to interference from coexisting salts, high reusability, good adsorption performance even after five reuse cycles, and a high desorption rate in a relatively short time. The adsorption performance in real brines could be maintained at 80%. Therefore, this work not only provided ECH@NGM aerogels for the removal of boron from brine but also elucidated the main adsorption processes between N-containing adsorbents and boron, facilitating the design of future adsorbents for boron removal.

Adsorption of acetone, ethyl acetate and toluene by beta zeolite/diatomite composites: preparation, characterization and adsorbability

The hierarchical porous composites (Beta/Dt) were prepared by secondary growth method using natural diatomite and beta zeolite. Moreover, XRD, SEM, and BET characterize the composite's composition, surface structure, and pore structure. The adsorbability of Beta/Dt was evaluated by adsorption of three common volatile organic compounds (VOCs) of the printing industry: acetone, ethyl acetate, and toluene. The results show that under the optimum preparation condition, the adsorption capacities of the three VOCs on Beta/Dt were about 3.5 times those of pure beta zeolite and 4.7-35.3 times those of diatomite, respectively. It indicates the synergistic adsorption effect between beta zeolite and diatomite. The superior adsorption capacity of Beta/Dt can be attributed to the suitable micropore size, the increase of the diffusion channels, and the chemical adsorption on modification diatomite. The adsorption of acetone, ethyl acetate, and toluene on Beta/Dt conformed to the pseudo-second-order kinetic model. In contrast, adsorption isotherms conformed to the Langmuir model, meaning that both physical and chemical adsorption occurred simultaneously during the adsorption process, and the adsorption belonged to the monolayer adsorption. The chemical adsorption mechanism can be ascribed to the nucleophilic reaction between the three VOCs (acetone, ethyl acetate, and toluene) and Beta/Dt with positive charges resulting from the modification diatomite. Furthermore, the composite could still keep more than 90% of the adsorption capacity of the original adsorbent after five regeneration cycles.

Coconut husk-raw clay-Fe composite: preparation, characteristics and mechanisms of Congo red adsorption

The release of unspent dyes from industries constitutes hazard and environmental challenges. For rapid and efficient removal of Congo red from aqueous solutions, a composite was prepared from coconut husk, raw clay, Fe(II) and Fe(II) compounds. Adsorption variables (initial pH of the solution, contact time, temperature and initial concentration of Congo red) were varied to understand the characteristics and mechanisms of the adsorption process. The composite was characterised using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM)–Energy dispersive X-ray (EDX) spectroscopy, nitrogen adsorption–desorption isotherm, X-ray Diffraction (XRD) spectroscopy and pH of the point zero charge (pH_pzc). The optimal values of the pH, equilibrium time and temperature for adsorption of Congo red by the composite are 2, 40 min and 50 °C, respectively. The kinetic and equilibrium data followed Avrami fractional order and Langmuir models, respectively. A 1.0 g of the composite could maximally take up 1649.3 mg of Congo red at 50 °C. The values of ΔG° are in the range of − 27.901 to − 24.492 kJ mol^–1 while the value of ΔH° is − 72.239 kJ mol^–1. Hence, the removal of the Congo red by the composite was spontaneous, feasible and exothermic. The adsorption process was biphasic and followed physisorption process. Electrostatic interaction played a significant role in the removal of Congo red by the composite. The combine data in this study have proven that the clay composite, a cheap adsorbent, can be used for remediation of water contaminated with Congo red.

Characterization of the remediation of chromium ion contamination with bentonite by terahertz time-domain spectroscopy

Heavy metal pollution of agricultural and urban soils limits economic progress in the rapidly developing society. Terahertz technology is applied to detect heavy metal pollutants under existence of multiple pathways of their dissemination. In this study, terahertz time-domain spectroscopy (THz-TDS) is employed as an advanced probing technique in combination with traditional detecting methods to measure the adsorption ability of trivalent chromium ions on bentonite. The concentration of chromium ions and the weight of bentonite are known to influence on the adsorption capacity of the latter. It is tested here by both qualitative and quantitative measurements of two mentioned parameters. The adsorption process of chromium ions by bentonite is monitored using THz-TDS. The adsorptions signal from samples at 0.5 THz gradually increases with the increase of bentonite weight or chromium ion concentration. It would appear to indicate that terahertz could be used for quantitative detection of metal ions. Secondly, the ratios of results obtained by inductively coupled plasma mass spectrometry (ICP-MS) and the THz-TDS ones are stabilized at 0.105  ±  0.014 as the bentonite weight or chromium ion concentration increase. Such finding confirms that terahertz technology can be used for the quantitative detection of metal ions. Using the relationship between the ICP-MS test results and the THz-TDS ones, the amplitude value of bentonite is obtained to be 13.925 at the concentration of chromium ions of 0.05 mol/L, the mass of bentonite sample involved in adsorption of 1.5 g, and the detection frequency in THz-TDS measurements of 0.5 THz. The adsorption coefficient of bentonite is calculated to be 1.44%. Increase of the chromium ion concentration to 0.2 mol/L, and the mass of bentonite involved in adsorption to 3 g leads to the increase of the amplitude corresponding to adsorbed chromium ions to about 19.463, and the adsorption coefficient to about 2.1%. Obtained results demonstrate that terahertz technology is promising to meet the ever-increasing requirements in mineral analyses for rapid detection of chemical contaminants and measurement of the adsorption efficiencies of materials.

Enzymatic hydrolysis lignin functionalized Ti3C2Tx nanosheets for effective removal of MB and Cu2+ ions

Functionalized two-dimensional Ti₃C₂T_x (TN-EHL) was prepared as an effective adsorbent for removal of methylene blue dye (MB) and copper ions (Cu²⁺). Enzymatic hydrolysis lignin (EHL), a reproducible natural resource, was used to functionalize the Ti₃C₂T_x nanosheets. EHL can not only introduce active functional groups into TN-EHL but also prevent the oxidation of Ti₃C₂T_x, thus promoting the adsorption performance of TN-EHL. The maximum adsorption capacities of TN-EHL50 (in which the EHL content is 50 wt%) for MB and Cu²⁺ were 293.7 mg g^-1 and 49.96 mg g^-1, respectively. The higher correlation coefficients (R²) of MB (0.9996) and Cu²⁺ (0.9995) indicating that their adsorption processes can be described by the pseudo-second-order kinetic model. The MB adsorption data fit the Freundlich isotherm with R² of 0.9953, whereas the Cu²⁺ ions adsorption data fit the Langmuir isotherm with R² of 0.9998. The thermodynamic analysis indicates that the adsorption process of MB and Cu²⁺ on TN-EHL50 is spontaneous and endothermic. Significantly, the Cu²⁺ ions were reduced to Cu₂O and CuO particles during the adsorption process. Therefore, TN-EHL has a great potential as an environmentally friendly adsorbent for MB removal and recovery of Cu²⁺ ions from wastewater.

Acid red 18 removal from aqueous solution by nanocrystalline granular ferric hydroxide (GFH); optimization by response surface methodology & genetic-algorithm

The need for fresh water is more than before by population growth, and industrial development have affected the quality of water supplies, one of the important reason for water contamination is synthetic dyes and their extensive use in industries. Adsorption has been considered as a common methods for dye removal from waters. In this study, Acid Red18 removal in batch mode by using Granular Ferric Hydroxide (GFH) was investigated. The GFH characterized by XRD, FESEM and FTIR analysis. Experiments were designed using RSM-CCD method. The maximum removal efficiency was obtained 78.59% at pH = 5, GFH dosage = 2 g/l, AR18 concentration = 77.5 mg/l and 85 min of contact time. Optimization with RSM and Genetic Algorithm carried out and is similar together. The non-linear adsorption Isotherm and kinetic fitted with Freundlich (R2 = 0.978) and pseudo-second-order (R2 = 0.989) models, respectively. Thermodynamic studies showed that the AR18 adsorption is endothermic process and GFH nature was found spontaneous.