Aqueous Solution Research Articles

Efficient adsorptive removal of low concentration fluoride ions from water by cellulose beads with trapped CeO2 nanoparticles

The high electronegativity and solubility of fluoride ions (F-) in water at low concentrations pose challenges for their treatment and recovery. To effectively adsorb F-, cellulose beads with trapped CeO2 nanoparticles (CeO2@CBs) were fabricated from a NaOH/urea aqueous solution by the optimal extrusion dropping technology. The CeO2@CBs exhibited a maximum removal efficiency of 99.15% for 10.0mgL-1 F- at 45°C, pH=3.0 and an adsorbent dose of 1.0g. The CeO2@CBs were characterized using SEM-EDS, FT-IR, XRD, and XPS. These findings demonstrate that CeO2 nanoparticles were uniformly entrapped in cellulose beads and reveal that the removal mechanism involves anionic exchange and electrostatic attractions between protonated hydroxyl on CeO2@CBs surface and F-. The results show that the anion competition sequence that affects the F- adsorption efficiency was Cl−<NO3−<SO42−<PO43−. CeO2@CBs were directly packed into columns, exhibiting exceptional adsorption efficacy and remarkable stability in column experiments. Even after three desorption cycles, the adsorption performance remained above 95%. Because the designed CeO2@CBs have a simple preparation process, high adsorption efficiency and environmental friendliness, they can provide valuable insights for designing new adsorbents and removing F- from aqueous solutions.

Sctudies on adsorption of Brilliant Green from aqueous solution onto nutraceutical industrial pepper seed spent

The study proposed the removal of Brilliant Green, a cationic dye, by adsorption process from wastewater solution utilizing a low-cost adsorbent such as Nutraceutical Industrial Pepper Seed Spent (NIPSS). The study comprises an investigation of the parametric influence on the adsorption process. The parameters identified are pH, dye concentration, process temperature, quantity of the adsorbent, and particle size. The study of statistics found from experiments was carried out by incorporating Freundlich, Brouers-Sotolongo, Langmuir, Toth, Sips, Jovanovic, and Redlich-Peterson isotherm models. The adsorption kinetics were determined by implementing pseudo-first-order and second-order models, diffusion film models, and Dumwald-Wagner and Weber-Morris models. The experimental adsorption capacity qe was found to be about 130 mg/g. This value was closest to the maximum adsorption of 144.6mg/g predicted by the Brouers-Sotolongo isotherm which had a correlation coefficient (R2) of 0.998. The adsorption kinetics data was confirmed to be a pseudo-second-order model. The change in free energy, enthalpy change, and entropy change were vital thermodynamic factors in concluding that adsorption is almost spontaneous and endothermic process. Change in enthalpy (ΔH°) reduced value indicates the physical nature of the process. The adsorption of BG dye on the adsorbent surface was authenticated by FTIR spectroscopy and SEM imaging. A Central Composite Design (CCD) Quadratic model under Response Surface Methodology (RSM) was implemented for statistical optimization of adsorption capacity for the five parameters studied, namely, time, temperature, concentration of the dye, weight of the adsorbent, and pH. Software Design Expert 7.0 was used to evaluate 3D contour plots. The process of optimization yielded a value of 350 mg/g. Thus, incrementing the adsorption process by 84.2 %. The study provides insights on various dye and adsorbent interaction possibilities and derives that NIPSS is an efficient adsorbent to extract BG dye from wastewater solutions.

Polyelectrolyte modified Ag-nanosphere: A Practical Approach for Sensitive and Selective SERS-based Detection of Organic Dye Pollutants

This study presents a cost-effective method for fabricating surface-enhanced Raman spectroscopy (SERS) substrates using Ag-nanospheres (AgNS) capped with Poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS). AgNS synthesis involves immersing Ag-nanocrystals in a nonaqueous solution, mixed with PEs in an aqueous solution via ultrasonic disturbance. Resulting aggregates form stable spherical assemblies with diameters ranging from 150 nm to 450 nm, and various characterization techniques, including scanning electron microscopy with energy-dispersive X-ray, UV-visible spectrophotometry, dynamic light scattering, and zeta potential analysis, were employed to analyze their fundamental chemical and physical properties. These qualified AgNSs serve as SERS substrates for sensitive and selective identification of charged organic dye contaminants, such as rhodamine 6G (R6G) and rose bengal (RB). Sensitivity assessments with the optimized quantities of either PDADMAC or PSS-capped AgNSs demonstrate successful detection down to concentrations of 10-14 M for RB and 4 x 10-13 M for R6G. The same SERS substrates also enable electrostatically driven selective detection even in analyte mixtures, and an additional variation of the SERS substrate comprising a complex of PDADMAC-capped and PSS-capped AgNSs exhibited distinct SERS spectra influenced by both positively and negatively charged analytes. Finally, successful detection of two oppositely charged pesticides was achieved through electrostatic attraction, so theses polyelectrolytes capped AgNS-based SERS substrate presents a promising avenue for efficiently and selectively detecting charged organic contaminants.

Phototransformation of tetrabromobisphenol A bis (allyl ether) in an aqueous solution: Role of environmentally persistent free radicals

Tetrabromobisphenol A bis (allyl ether) (TBBPA-BAE) represents an extensively used brominated flame retardant (BFRs) in the production of many fields and their phototransformation in natural water is still unclear. The environmentally persistent free radicals (EPFRs) with preserved activities could exist in the environment for a long time and involve in the phototransformation of many organic pollutants. Here, the photodegradation of TBBPA-BAE with the degradation rate constant (k= 0.060 h-1) under simulate sunlight and the promoting effect of EPFRs on TBBPA-BAE photodegradation (k = 0.135 h-1) were investigated. According to the detected photogenerated electrons (e-) and singlet oxygen (1O2) rather than hydroxyl radicals (•OH) by the electron paramagnetic resonance (EPR), the effect mechanism may not be related to the typical •OH induced by EPFRs. The possible transformation pathways of the ether cleavage, hydrolysis and hydroxylation of propenyl bond and the debromination were proposed by the primary byproducts identified by UPLC-Q-Exactive Orbitrap MS. EPFRs caused a further debromination and ether cleavage and probably be due to EPFRs directly providing electrons to TBBPA-BAE which promoted the photodegradation of TBBPA-BAE, and their reaction mechanism needed further attention. Overall, this study provided useful information to understand the role of EPFRs on phototransformation of TBBPA-BAE in water.

Sulphonated Poly (Glycidyl Methacrylate-co-Styrene)-based Adsorbents for the Removal of Methylene Blue (MB) Dye from Aqueous Solutions

Sulphonated Poly (Glycidyl Methacrylate-co-Styrene)-based Adsorbents for the Removal of Methylene Blue (MB) Dye from Aqueous Solutions

Polymer coating by oxidative polymerization of a new dopamine analogue with two amino groups

In our quest to expand the comprehensive chemistry of polydopamine and its catechol-containing analogous adhesive polymers we developed a new monomer, specifically 4-[3-amino-2-(aminomethyl)propyl]benzene-1,2-diol ADA. This compound is an analogue of dopamine characterized by an elongated and branched alkyl side chain that incorporates two amino groups. ADA was synthesized in two steps from 3,4-dihydroxybenzaldehyde in high yields. Exposure to air in aqueous Tris solution initiated polymerization leading to a dark colored product PADA that can adhere to surfaces forming continuous layers. The product was analyzed by FTIR, NMR, UV-vis-spectroscopy, AFM, HR-ESI-MS spectrometry, XPS, DPV, DLS and contact angle measurement. Based on these analyses, a general structure of the product is proposed as along with a mechanism of its formation. Notably, the properties of PADA are distinct from those of polydopamine offering different potential application. In particular, the additional amino groups could be used for interesting linkage of other functional moieties.

Removal of Cu(II) from aqueous solutions by novel EDA-functionalized clay nanocomposite fabricated as nanoadsorbents

Removal of Cu(II) from aqueous solutions by novel EDA-functionalized clay nanocomposite fabricated as nanoadsorbents

Iota-carrageenan as a regenerating system for Eu3+ recovery: adsorption/desorption cycles

ABSTRACT Renewable and biodegradable polysaccharides attract attention as environmentally friendly adsorbents for the removal of heavy metals from wastewater. One such group, is carrageenan, of which were recently successfully employed to adsorb representative lanthanide and actinide ions. Herein, iota-carrageenan-based hydrogels were used to adsorb europium ions (Eu3+) from water solutions, followed by desorption of the ions from the hydrogel beads and recycling of the beads three times. It was found that sorption yields from a 500 mg/L Eu3+ ion solution with beads that were prepared with 1 or 2 wt/v% aqueous solution of iota-carrageenan with CaCl2 (0.5 M) reached maximum sorption yield of 50% and 65%, correspondingly, after 1 h. In addition, the sorption kinetics followed the pseudo second-order model controlled by chemisorption. Desorption yields in the first cycle using NaNO3 (1 M) with both preparations were 57% and 74%, respectively. The sorption yields increased during the second and third cycles and were efficient in the overall pH range. Cryo-SEM, SEM, SEM-EDS and TGA analyses verified the adsorption and desorption of Eu3+ ions to and from the iota beads and that the Ca2+ ions that initially crosslinked the hydrogel were replaced during the cycles by Eu3+ or Na+ ions. In addition, the beads were stable and easily reusable for several sorption/desorption cycles. Furthermore, after sorption, the beads were characterised by a porous structure, such that beads prepared with a 2 wt/v% aqueous solution of iota-carrageenan yielded a more porous, ordered structure, and after desorption, the bead textures became even more porous.

Highly efficient removal of uranium (VI) from aqueous solutions by APTES/ATP

Abstract Uranium-containing wastewater poses a significant threat to both the ecological environment and human health. Adsorption is a crucial method for purifying uranium wastewater. Using 3-Aminopropyltriethoxysilane (APTES) to modify attapulgite (ATP), we successfully prepared a cost-effective and high-performance adsorbent material, APTES-modified attapulgite (APTES/ATP). This material was utilized for the purification of uranium-containing wastewater. Characterization techniques were employed to study the structure and surface properties of the material. The adsorption performance of the material was investigated using single-factor experiments. The adsorption isotherms, kinetics, and thermodynamics were also studied and discussed. The results indicated that APTES/ATP exhibited an adsorption capacity of 382.13 mg·g⁻¹ for uranium at room temperature. The adsorption process followed the Langmuir adsorption model and pseudo-second-order kinetics, indicating that the adsorption of uranium by the material was a monolayer chemisorption. Adsorption thermodynamics revealed that the process was endothermic and spontaneous. The adsorption mechanism primarily involved electrostatic attraction and interactions between -NH₂, Si-O, and -OH groups with uranium. In summary, the prepared APTES/ATP demonstrated excellent adsorption capacity for uranium and shows promise for the purification of uranium-containing wastewater.

The effect of Sodium Dodecyl Sulfate on Polysulfone membrane for Pb (II) ions removal in an aqueous solution

The effect of Sodium Dodecyl Sulfate on Polysulfone membrane for Pb (II) ions removal in an aqueous solution

Swelling Kinetics of Hydrogel Beads in Aqueous Glycerin Solutions

Swelling Kinetics of Hydrogel Beads in Aqueous Glycerin Solutions

Room-Temperature Synthesis of Au@AuCu Alloyed Nanorods in Aqueous Solutions for High Catalytic Activity and Enhanced Stability

Room-Temperature Synthesis of Au@AuCu Alloyed Nanorods in Aqueous Solutions for High Catalytic Activity and Enhanced Stability

Algae Modified Alginate Beads for Improved Cd(II) Removal from Aqueous Solutions

The aim of this research was to synthesize alginate beads. The beads were modified with a mixture of three different species of algae. Both synthesized beads were evaluated for the efficiency of Cd(II) removal from aqueous solutions as one of the currently most sustainable metal removal methods. The focus was on the characterization of synthesized beads and their stability. The characterization was performed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The specific surface area was determined. Cd(II) ion standard solutions were brought into contact with unmodified and modified beads. The experimental results showed that the most influential factors on biosorption are pH value and temperature. The maximum biosorption of Cd(II) ions was achieved at 181.0 mg/g. Kinetic and thermodynamic studies were carried out. The data obtained followed pseudo-second-order kinetics.

Dynamic behavior of a fixed-bed adsorption column for acid red removal using natural Algerian cactos

In this work, the ability of Natural Algerian Cactus (NAC) to adsorb Acid Red (AR) from aqueous solution was investigated in a fixed-bed column. Scanning Electron Microscopy (SEM) was employed to examine the surface of the biosorbent, Fourier Transform Infrared Spectroscopy (FTIR) was utilized to analyze the chemical composition of NAC, and Brunauer-Emmett-Teller (BET) analysis was conducted to determine the surface area of NAC. We examined the effects of flow rate and influent concentration of AR on the efficiency of the fixed bed. Additionally, we analyzed the sorption of AR using the Thomas and Yoon-Nelson models at various dye concentrations and flow rates to predict breakthrough curves and determine the characteristic parameters of the fixed bed sorption column. The applied models were found to describe the NAC column biosorption process. The obtained results show that the natural Algerian cactus is an efficient Acid Red biosorbent from its aqueous solutions. A sorption capacity of 39.51 mg/g was recorded for the highest concentration (100 mg/l) at a flow rate of 0.8 mL/min while for the highest flow rate (2 mL/min), the sorption capacity attained 30.27 mg/g for a concentration of 50 mg/l. However, the longest breakthrough time was noted for the lowest concentration and flow rate respectively (tb=21h and te=38h for 50mg/l and 0.8 mL/min).

A high‐temperature resistant benzimidazole‐based porous polymer for efficient adsorption of trinitrotoluene in aqueous solution

AbstractA novel benzimidazole‐based porous polymer, denoted as PTBI, was synthesized utilizing self‐synthesized 1,3,5‐tris(1H‐benzo[d]imidazol‐2‐yl)benzene (TBI) and 4,4′‐difluorobenzophenone as primary materials via a CN coupling reaction, followed by a freeze‐drying process. PTBI displayed commendable thermal stability, as evidenced by a temperature of 475°C at which a 5% weight loss occurred and a char yield of up to 65% at 800°C. Trinitrotoluene (TNT) was effectively adsorbed by PTBI in aqueous solutions, thanks to the combined effects of three π–π interactions and one dipole–π interaction. At 25°C, PTBI achieved a maximum adsorption capacity as high as 280.8 mg/g, with approximately 60% of this capacity attained within just 1 h. Furthermore, a thermodynamic analysis showed that the adsorption of TNT by PTBI was a spontaneous, exothermic process that was followed by a decrease in entropy. It is noteworthy that following five adsorption and desorption cycles, the adsorption efficiency held steady at a relatively high level using acetone as the eluent. These promising results underscore PTBI's significant potential in the realm of TNT wastewater treatment, positioning it as a compelling candidate for further research and application under extreme condition in this field.

Green Synthesis of Iron-Based Nanoparticles Using Pomegranate Leaf Extracts: Characterization, Biomolecules and Indole Removal

This study investigates the synthesis of iron-based nanoparticles (Fe NPs) using pomegranate leaf extracts and their application in removing indole, a persistent organic pollutant commonly found in wastewater. The physicochemical properties of the synthesized Fe NPs and the active biomolecules in the pomegranate leaf extracts were comprehensively characterized. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses revealed that the Fe NPs exhibited quasi-spherical shapes, with sizes ranging from 75 to 105 nm. Energy-Dispersive X-ray Spectroscopy (EDS) confirmed a homogeneous distribution of elements, including C, O, Fe, and S, on the nanoparticle surfaces, with weight percentages of 43.59%, 42.95%, 12.58%, and 0.88%, respectively. Fourier-transform infrared spectroscopy (FTIR) identified key functional groups like −OH, −COOH, and −C=O, which are essential for the capping and stabilization of the nanoparticles. Biomolecules such as ellagic acid (C14H6O8) and gallic acid (C7H6O5) functioned as reducing agents, improving nanoparticle dispersion and preventing aggregation. The synthesized Fe NPs quickly achieved 45.5% removal of indole within just 20 min and maintained a stable removal efficiency of approximately 51.4% after 90 min. This performance was attributed to the synergetic interaction between the biomolecules and the nanoparticles, with the monolayer adsorption of indole molecules on the Fe NP surfaces likely setting an upper limit on the maximum achievable removal efficiency. It appears from this study that pomegranate leaf extracts can be effectively utilized to synthesize Fe NPs as a novel and eco-friendly approach, demonstrating promising potential for the rapid removal of indole from aqueous solutions.

Calcium silicate hydrate complex konjac glucomannan-based hydrogel selectively adsorbed phosphate in low alkalinity solution

The selective recovery of phosphate from wastewater can manage nutrients and realize the recycling of phosphorus resources. In this study, a novel konjac glucomannan/pectin/calcium silicate composite hydrogel (KP-CSH) was developed for efficient recovery of phosphate in aqueous solution. The amount of alkali released after the reaction of KP-CSH in a neutral solution was small (the pH of the solution after the reaction was < 9). In a wide initial pH range (3–10), the adsorption capacity of KP-CSH in 50 mg-P/L phosphate solution reached 39∼45 mg-P/g. Besides, even if the pH of the solution after the reaction was less than 8, it could still well adsorb phosphate. The kinetic and isothermal adsorption experiments indicated that the adsorption process of phosphate by KP-CSH was chemical adsorption, and the maximum adsorption capacity was 61.2 mg-P/g. KP-CSH preferentially adsorbed phosphate even in the presence of high concentrations of competitive ions. In the actual biogas slurry, KP-CSH also exhibited the strongest selectivity/affinity for phosphate, and its distribution coefficient (Kd) was significantly higher than that of other co-existing anions and cations. The adsorption mechanism analysis indicated that Ca was the main adsorption site of KP-CSH, and that the adsorption process of target pollutants mainly involved ligand exchange and the intra-sphere complexation. Further plant seed germination and seedling growth experiments suggested that KP-CSH after phosphate recovery did not exert a negative effect on the growth of plant seedlings, and increased the chlorophyll content of seedling leaves. These results demonstrate that KP-CSH is a potential adsorbent for efficient phosphate recovery, which can be used as a slow-release phosphate fertilizer after recovering phosphate.

Enhanced cadmium (Cd2+) removal from wastewater using integrated inclined plate settler and composite adsorbent coating

Bottlenecks inherent in batch and column adsorption configurations have impeded the implementation of the adsorption technique in large-scale wastewater treatment systems. This study mainly aimed to develop an innovative wastewater treatment prototype that integrates inclined plate settlers (IPS) and composite adsorbent coating (CAC). The objective is to enable the removal of Cd2+ from aqueous solutions in a continuous setup, thereby enhancing its practicality for large-scale applications. The combined IPS-CAC system was optimized at various angle of inclination (θ), influent flow rate (Q) and adsorbate initial concentration (Co) using the Box–Behnken Design (BBD) of the Response Surface Methodology (RSM). At optimized operating parameters (θ = 45°, Q = 5 ml/min and Ci = 1.87 mg/L) the IPS-CAC Cd2+ predicted (R2 = 0.9926) and experimental removal efficiencies were 75.8% and 69.7 ± 4.67%, respectively. The IPS-CAC breakthrough adsorption capacity was 9.6 mg/g. Comparing IPS-CAC performance with a tank without plates and IPS with plain plates, the Cd2+ removal efficiencies were 2.4 ± 0.1% and 4.6 ± 1.1%, respectively, confirming the synergistic effect of IPS and CAC. Additionally, breakthrough curves were acquired for various flow rates, cadmium influent concentrations, and plate inclination angles. Only a 10% decline in the removal effectiveness (from 69.7 to 59.7%) of the CAC after three adsorption–regeneration cycles was observed, indicating its stability for heavy metal removal. The results underpin the potential of using IPS-CAC for industrial wastewater treatment and enhancing the use of adsorption on a larger scale.

Facile synthesis of rGO/ZnCo2O4 nanocomposite for enhanced photocatalytic dye degradation of crystal violet dye solution

The rGO/ZnCo2O4 nanocomposite (NCs) was synthesized using a hydrothermal method. The crystallite size, morphology, and optical properties of rGO, ZnCo2O4, and the rGO/ZnCo2O4 nanocomposite were extensively characterized using TG/DTA, FT-IR, UV-DRS, XRD, SEM with EDAX, and TEM techniques. The synthesized rGO/ZnCo2O4 NCs were crystalline with a cubic spinel structure and an average crystallite size of 19 nm, as confirmed by XRD. The optical bandgaps of pure ZnCo2O4 and the rGO/ZnCo2O4 nanocomposite were estimated to be 2.3 eV and 1.8 eV, respectively. The crystal violet (CV) dye was efficiently removed from an aqueous solution by photocatalytic degradation under visible light and sunlight irradiation in the presence of pure ZnCo2O4 and the rGO/ZnCo2O4 nanocomposite. The degradation results revealed that nearly 99.9 % of dye degradation was achieved with the rGO/ZnCo2O4 nanocomposite compared to pure ZnCo2O4 nanoparticles in 60 minutes. Hence, the rGO/ZnCo2O4 nanocomposite can be considered a promising and efficient photocatalyst for the degradation of crystal violet dye. The key highlight of this work is the low-cost, disruptive engineering strategy for synthesizing nanocatalysts for multifaceted applications.

Adsorption behavior of graphite‐like walnut shell biochar modified with ammonia for ciprofloxacin in aqueous solution

AbstractBACKGROUNDGraphite‐like biochar of NWSC600K was prepared at 900 °C using walnut shell as the raw material and aqueous ammonia (NH3·H2O) as an activator, and characterized using transmission and scanning eletron microscopy (TEM, SEM), X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy and Fourier transform infrared (FTIR). The study investigated the adsorption performance and mechanism of NWSC600K for ciprofloxacin (CIP).RESULTSThe results showed that extremely tiny pores were found on the surface of NWSC600K, which increased its specific surface area to 823.91 m2 g−1, whereas the average pore size of NWSC600K decreased to 3.23 nm. The results of TEM, XRD and Raman spectroscopy detected well‐arranged lattice stripes as well as characteristic peaks corresponding to the graphite lattice appearing on the surface of NWSC600K. Moreover, the ID/IG value for NWSC600K was 1.429. The FTIR results showed that functional groups including the amino group were formed on NWSC600K.CONCLUSIONThe adsorption capacity of NWSC600K for CIP was 158.14 mg g−1 and the corresponding removal rate was 97.5% at pH 7. The pH value impact on the removal efficiency of CIP greatly, and the removal rate of CIP decreased linearly with increasing pH. The coexisting ions also would inhibit the adsorption of CIP on NWSC600K. Results obtained from kinetic and isotherm models, thermodynamics and characterization analyses suggested that pore‐filling, π–π stacking, hydrogen bonding, hydrophobicity and electrostatic interaction existed during the adsorption process. The adsorption was a nonspontaneous exothermic reaction. © 2024 Society of Chemical Industry (SCI).