Spontaneous Adsorption Research Articles

Enhanced dye adsorption with conductive polyaniline doped chitosan nanofibrous membranes

Polyaniline is widely used in the field of electrochemistry due to its excellent electrical conductivity. However, its effectiveness and mechanism of enhancing adsorption property are unclear. Herein, chitosan/polyaniline nanofibrous composite membranes with average diameter ranging from 200 to 300 nm were fabricated by electrospinning technology. The as-prepared nanofibrous membranes exhibited significantly improved adsorption capacity of 814.9 mg/g and 618.0 mg/g towards acid blue 113 and reactive orange dyes, which were 121.8 % and 99.4 % higher than that of pure chitosan membrane. The doped polyaniline promoted the dye transfer rate and capacity due to the enhanced conductivity of the composite membrane. Kinetic data showed that chemisorption was the rate-limiting step, and thermodynamic data indicated the adsorption of the two anionic dyes was spontaneous monolayer adsorption. This study provides a feasible strategy to introduce conductive polymer into adsorbent to construct high performance adsorbents for wastewater treatment.

Polypyrrole-decorated Mg-Al layered double oxides for dye adsorption: Isotherm, kinetics, and thermodynamic investigations

Polypyrrole-decorated Mg-Al layered double oxides (PPy/Mg-Al) were prepared via the in-situ polymerization for enhancing the adsorption capacity of Rhodamine B (RhB). For comparison to Mg-Al layered double oxides, PPy/Mg-Al composites presented the better adsorption capacity, which climbed and then declined with an increase PPy content. The optimal 2-PPy/Mg-Al had the best Langmuir adsorption capacity of 200.10 mg g−1, and its tested adsorption capacity decreased from 137.13 to 118.13 mg g−1 after seven cycles due to the change in the valance sates of surface compositions and surface discharge nature. 2-PPy/Mg-Al exhibited a spontaneous and endothermic adsorption process for RhB removal, and its adsorption isotherms and kinetics were respectively described by Langmuir and second-order models. Hence, the in-situ polymerization of pyrrole was a promising route to enhance the adsorption activity of Mg-Al LDO for dyes removal from wastewater.

Cysteine as an Alternative Eco-Friendly Corrosion Inhibitor for Absorption-Based Carbon Capture Plants.

Inorganic corrosion inhibitors are commonly applied to mitigate severe corrosion in absorption-based carbon capture plants. They are, however, not environmentally friendly, posing a health risk, harming the environment, and making chemical handling and disposal costly. Therefore, this study evaluated the corrosion inhibition performance of an amino acid, namely cysteine, with the aim of providing an eco-friendly alternative to the commercial inorganic corrosion inhibitors. Electrochemical and weight loss corrosion measurements showed that cysteine was effective in protecting carbon steel at all process operating conditions. At 80 °C, a 500 ppm cysteine could provide up to 83% and 99% inhibition efficiency under static and dynamic flow conditions, respectively. Its inhibition efficiency could be improved when the cysteine concentration, solution temperature, and flow condition were altered. Cysteine was an anodic corrosion inhibitor and underwent spontaneous, endothermic, and combined physical and chemical adsorption that followed the Langmuir adsorption isotherm model. The quantum chemical analysis indicated that cysteine had a high reactivity with metal surfaces due to its low energy gap and high dipole moment. The EDX analysis revealed a significant sulphur content on the metal substrate, indicating that cysteine's mercapto group played an integral role in forming an effective adsorption layer on the metal interface.

Rapid adsorptive removal of chromium from wastewater using walnut-derived biosorbents

Contamination of water resources by industrial effluents containing heavy metal ions and management of solid waste from agricultural and food industries is a serious issue. This study presents the valorization of waste walnut shells as an effective and environment-friendly biosorbent for sequestrating Cr(VI) from aqueous media. The native walnut shell powder (NWP) was chemically modified with alkali (AWP) and citric acid (CWP) to obtain modified biosorbents with abundant availability of pores as active centers, as confirmed by BET analysis. During batch adsorption studies, the process parameters for Cr(VI) adsorption were optimized at pH 2.0. The adsorption data were fitted to isotherm and kinetic models to compute various adsorption parameters. The adsorption pattern of Cr(VI) was well explained by the Langmuir model suggesting the adsorbate monolayer formation on the surface of the biosorbents. The maximum adsorption capacity, qm, for Cr(VI) was achieved for CWP (75.26 mg/g), followed by AWP (69.56 mg/g) and NWP (64.82 mg/g). Treatment with sodium hydroxide and citric acid improved the adsorption efficiency of the biosorbent by 4.5 and 8.2%, respectively. The endothermic and spontaneous adsorption was observed to trail the pseudo-second-order kinetics under optimized process parameters. Thus, the chemically modified walnut shell powder can be an eco-friendly adsorbent for Cr(VI) from aqueous solutions.

Adsorption kinetic studies of octyl hydroxamic acid on galena surface

In this work, octyl hydroxamic acid (OHA) was utilized as a collector for galena flotation, and its adsorption kinetics on galena surface was fully studied. The experimental results showed that the optimal pH for the adsorption was 9.5 and the adsorption equilibrium was reached at 2 h. It is important to emphasize that this process was an exothermic, spontaneous, ordered and monolayer adsorption. In addition, the adsorption of OHA on galena surface could change the surface charges and improve the surface hydrophobicity, as identified by zeta potential and contact angle measurements, respectively. XPS analysis demonstrated that OHA chemisorbed on the galena surface mainly through the binding reactions between the two O atoms of -C(=O)–NHOH group and Pb(OH)+ on galena surface at pH 9.5. Flotation experimental demonstrated that 4 × 10-5 mol/L OHA could collect 98.62% of galena at pH 9.5, which was higher than that by sodium isopropyl xanthate (SIPX) under the same experimental conditions.

New pyrazole derivative as effective corrosion inhibitor for carbon steel in 1 M HCl: Experimental and theoretical analysis

Corrosion inhibition is an extensive field of study, and its progression is gaining traction among researchers. This paper describes a study to synthesize and characterize a novel class of organic corrosion inhibitor called (3, 5-dimethyl-1H-pyrazol-1-yl) (4-((4-chlorobenzy-lidene) amino) phenyl) methanone) (DPCM). The structure of DPCM was determined using FTIR, 1H NMR and 13C NMR techniques. The effectiveness of DPCM was tested on carbon steel in 1 M HCl using electrochemical and weight loss methods, and it was found that the inhibition efficiency increased with increasing temperature and DPCM concentration. The highest inhibition efficiency of 89.5% was achieved at 60 °C and 400 ppm DPCM. The inhibition action of DPCM molecules was achieved by blocking the metal surface by means of the adsorption of inhibitor molecules obeying the Langmuir adsorption isotherm. Adsorption-free energy indicates a spontaneous chemical adsorption process. The polarization test results clarified a mixed effect of DPCM on anodic and cathodic reactions. Electrochemical impedance spectroscopy indicated an increase in metal resistance in the presence of an inhibitor. The formation of a protective layer was confirmed by SEM and AFM analysis. Density functional theory (DFT) simulation has been used to determine the relationship between molecular configuration and their inhibition efficiencies.

Preparation of a novel high-performance lignin-based anionic adsorption resin for efficient removal of Cr(VI) in aqueous solutions

To remove Cr(VI) in water, a novel lignin-based anionic adsorption resin epichlorohydrin cross-linking lignin grafted by diethylenetriamine (E-DAL) was prepared by the direct cross-linking and curing of alkali lignin grafted by diethylenetriamine in aqueous solutions. Under the determined optimum synthesis conditions, E-DAL with higher nitrogen (7.46%) and lignin (32.78%) contents was obtained. Structural and physicochemical measurement results showed E-DAL was a macroporous resin, having a regular connected pore structure with porosity of 67.48% and pore size of 615.6 nm, also strong hydrophilicity, excellent acid-alkaline resistance and thermal stability. Adsorption experiment results indicated the adsorption isotherm of E-DAL to Cr(VI) was well-described by Langmuir model. E-DAL showed a higher adsorption capacity to Cr(VI), and the fitted maximum adsorption capacity reached up to 775.2 mg/g. Pseudo-second-order model could fit this adsorption process well, suggesting its chemisorption characteristics. The calculated thermodynamic parameters indicated a spontaneous and endothermic adsorption of E-DAL to Cr(VI). Dynamic column adsorption results showed E-DAL could completely remove Cr(VI) in wastewater. This whole preparation process only used a very small amount of cheaper amination agent and was relatively low-cost. This work provided efficient technical supports for the structural design of high-performance lignin-based anionic adsorption materials in water treatment field.

Textural properties and adsorption behavior of Zn–Mg–Al layered double hydroxide upon crystal violet dye removal as a low cost, effective, and recyclable adsorbent

The preparation of adsorbents plays a vital role in the adsorption method. In particular, many adsorbents with high specific surface areas and unique shapes are essential for the adsorption strategy. A Zn–Mg–Al/layer double hydroxide (LDH) was designed in this study using a simple co-precipitation process. Adsorbent based on Zn–Mg–Al/LDH was used to remove crystal violet (CV) from the wastewater. The impacts of the initial dye concentration, pH, and temperature on CV adsorption performance were systematically examined. The adsorbents were analyzed both before and after adsorption using FTIR, XRD, and SEM. The roughness parameters and surface morphologies of the produced LDH were estimated using 3D SEM images. Under the best conditions (dose of adsorbent = 0.07 g and pH = 9), the maximum adsorption capacity has been achieved. Adsorption kinetics studies revealed that the reaction that led to the adsorption of CV dye onto Zn–Mg–Al/LDH was a pseudo-second-order model. Additionally, intraparticle diffusion suggests that Zn–Mg–Al/LDH has a fast diffusion constant for CV molecules (0.251 mg/(g min1/2)). Furthermore, as predicted by the Langmuir model, the maximal Zn–Mg–Al/LDH adsorption capacity of CV was 64.80 mg/g. The CV dimensionless separation factor (RL) onto Zn–Mg–Al/LDH was 0.769, indicating that adsorption was favorable. The effect of temperature was performed at 25, 35, and 45 °C in order to establish the thermodynamic parameters ∆Ho, ∆So, and ∆Go. The computed values indicated exothermic and spontaneous adsorption processes. The study presented here might be used to develop new adsorbents with enhanced adsorption capabilities for the purpose of protecting the water environment.

Aqueous Pb(II) Removal Using ZIF-60: Adsorption Studies, Response Surface Methodology and Machine Learning Predictions.

Zeolitic imidazolate frameworks (ZIFs) are increasingly gaining attention in many application fields due to their outstanding porosity and thermal stability, among other exceptional characteristics. However, in the domain of water purification via adsorption, scientists have mainly focused on ZIF-8 and, to a lesser extent, ZIF-67. The performance of other ZIFs as water decontaminants is yet to be explored. Hence, this study applied ZIF-60 for the removal of lead from aqueous solutions; this is the first time ZIF-60 has been used in any water treatment adsorption study. The synthesized ZIF-60 was subjected to characterization using FTIR, XRD and TGA. A multivariate approach was used to investigate the effect of adsorption parameters on lead removal and the findings revealed that ZIF-60 dose and lead concentration are the most significant factors affecting the response (i.e., lead removal efficiency). Further, response surface methodology-based regression models were generated. To further explore the adsorption performance of ZIF-60 in removing lead from contaminated water samples, adsorption kinetics, isotherm and thermodynamic investigations were conducted. The findings revealed that the obtained data were well-fitted by the Avrami and pseudo-first-order kinetic models, suggesting that the process is complex. The maximum adsorption capacity (qmax) was predicted to be 1905 mg/g. Thermodynamic studies revealed an endothermic and spontaneous adsorption process. Finally, the experimental data were aggregated and used for machine learning predictions using several algorithms. The model generated by the random forest algorithm proved to be the most effective on the basis of its significant correlation coefficient and minimal root mean square error (RMSE).

3D graphene sponge biomass-derived with high surface area applied as adsorbent for nitrophenols

The present work used wood sawdust as a carbon precursor to produce 3D graphene sponge material, a carbon material with an added value, successfully used as an adsorbent for removing o-nitrophenol and p-nitrophenol from aqueous effluents. The resulting material’s structural, morphological, textural, and chemical characteristics (WS-Graphene) were evaluated. Textural analysis revealed a high surface area (∼3000 m2g−1) and high total pore volume (1.38 cm3 g−1). Raman, infrared and X-ray diffraction techniques evidenced the presence of a few layers of graphene, with some fraction of defects. Transmission electron microscopy confirmed the presence of a 3D-packed structure for the graphene. These WS-Graphene characteristics favored its application as an adsorbent for removing o-nitrophenol and p-nitrophenol pollutants. The adsorption process of both nitrophenols was extremely rapid and reached the equilibrium time in less than 5 min when the concentration of both adsorbates was fixed at 700 mg L−1. Furthermore, the maximum adsorption capacity (Qmax) values were 1842 mg g−1 (o-nitrophenol) and 879.6 mg g−1 (p-nitrophenol) at 30 °C. These results confirm that the WS-Graphene adsorbent acts as a 3D sponge. Langmuir’s isothermal was the best-fitted model for both nitrophenols in aqueous solution. The o-nitrophenol adsorption onto WS-Graphene might follow pseudo-second-order as well as general-order, while the adsorption of p-nitrophenol might follow only the general-order model. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The WS-Graphene adsorbent presents a high percentage (∼97 %) of removing the mixture of pollutants in effluents, showing an excellent adsorption capacity and making it a potential material to remove industrial wastewater.

Spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle for rapid and selective extraction of uranium

Iron oxide with superparamagnetic property and mesoporous silica with large surface areas are both important to design multifunctional sorbents, and magnetic-mesoporous nanoparticles of asymmetric morphology may make full use of their advantages. To address this, spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle with abundant amidoxime (AO) groups (AO-Fe3O4@C&mSiO2) was synthesized for rapid and selective extraction of uranium. Chemically and structurally anisotropic AO-Fe3O4@C&mSiO2 was composed of one AO functionalized mesoporous silica nanorods and a carbon coated Fe3O4 nanoparticle, which displayed excellent surface area (139.9 m2 g−1) and saturation magnetization (28.79 emu g−1). Thus, AO-Fe3O4@C&mSiO2 showed fast adsorption kinetics for reaching adsorption equilibrium within 30 min, and then they were able to be collected in 3.0 s under an external magnetic field. The maximum and spontaneous adsorption capacity for uranyl ions was obtained by fitting thermodynamic data through Langmuir model at 298 K was 62.12 mg g−1, and AO-Fe3O4@C&mSiO2 achieved the highest uptake amount and removal rate of almost 100% towards uranium in the presence of competitive ions. Meanwhile, the results from ten regeneration cycles confirmed the high service lifetime of AO-Fe3O4@C&mSiO2. This work not only demonstrates a strategy for preparing multifunctional sorbents with anisotropic structure but also provides a method for selective uranium extraction.

Interface engineering toward self-corrosion inhibited alkaline aluminum-air battery via optimized electrolyte system

In this manuscript, an introduced ionic liquids-ethylene glycol-KOH electrolyte system is proposed. Theoretical calculations and experiments show that ionic liquids with stronger hydrophobicity provide better corrosion inhibition for their spontaneous adsorption behavior and water molecule segregation. In this process, the imidazole ring cations play a major role. The electrolyte system reconstructs the Al/electrolyte interface with poor H2O, thus has lower self-corrosion rate for [BMIM]PF6 and contributes to the uniform dissolution of Al anode. Additionally, discharge performance of the full-cell feature same trend, endowing an outstanding capacity of 1971 mAh g−1 and anode utilization of 66.2% in alkaline [BMIM]PF6-ethylene glycol electrolyte. In terms of maintaining the activity of the Al-6061 anode whilst keeping low corrosion rate level, the proposed electrolyte system seems to be potential alternative.

Barbituric acid derived covalent organic framework and its CNT composite as high-performance adsorbents for organic dye removal

Herein, we report for the first time, the synthesis of Barbituric acid (BA) based Covalent Organic Framework (COF) and its composite with Carbon NanoTubes (CNT), for efficient and selective dye removal. The adsorbents were characterized using solid state 13C NMR, PXRD, FT-IR, BET, FEG-SEM and TGA. Higher porosity and surface area facilitates efficient adsorption process. Batch experiments for dye adsorption were performed for Malachite Green (MG) and Methyl Orange (MO) as well as mixed dye to determine the adsorption capacity, removal efficiency and adsorption mechanism. The experimental results best fits Langmuir isotherm model and follows Pseudo second order kinetics. The maximum adsorption capacity was as high as 553.55 mg/g and 226.12 mg/g for MG and MO respectively, using COF. The COF-CNT composite showed even higher values viz. 603.91 mg/g and 234.57 mg/g for MG and MO. Moreover, the adsorption performance of these adsorbents in binary dye mixture exhibited the potential of COF for dye separation and that of COF-CNT for simultaneous dye removal. Thermodynamic studies demonstrated endothermic and spontaneous adsorption process. The regeneration studies reveal the potential of these adsorbents to be reused for multiple cycles. These adsorbents with high adsorption efficiency can act as promising and recyclable materials for practical wastewater treatment.

In-situ conversion of geopolymer into novel floral magnetic sodalite microspheres for efficient removal of Cd(II) from water

In the present work, a novel, floral-like, magnetic sodalite microsphere (SODM) was synthesized in situ by using fly ash (FA) and metakaolin (MK) as raw materials and was used to remove Cd(II) from water. Its magnetism can solve the problems of adsorbent recovery and possible secondary pollution. During the static adsorption, SODM shows a maximum adsorption capacity of 245.17 mg/g. The adsorption of Cd(II) on the SODM surface is spontaneous, exothermic, and physicochemical adsorption, which was evaluated by thermodynamics, kinetics, and isotherm studies. During dynamic adsorption, SODM shows a maximum adsorption capacity of 342.74 mg/g in the simulated solution prepared by the deionized water, compared to 215.88 mg/g in the simulated solution prepared using Xiangsi Lake water from Guangxi Minzu University. At 0.5 g SODM dosage in the dynamic adsorption, the adsorption capacity could rise to 632.81 mg/g. These results demonstrated the excellent Cd (II) adsorption performance of the SODM. The adsorption of cadmium on the SODM surface includes the synergistic effects of electrostatic attraction, ion exchange, and surface coordination reaction. Besides, the SODM shows good regeneration performance in both the deionized water and Xiangsi Lake water. The present study explores SODM as an adsorbent for the Cd (II) removal from wastewater and unbolts the industrial applicability of the SODM in the field of wastewater purification.

Development and optimization of geopolymer adsorbent for water treatment: Application of mixture design approach

The current paper refers to the study of a new approach to optimizing the adsorptive properties of geopolymers by varying the aluminosilicate precursors from kaolin (K), metakaolin (MK), and coal fly ash (CFA) as internal synthesis factors. The simplex-augmented-centroid mixture design was applied to identify the optimal formulation from the three aluminosilicate precursors to develop a geopolymer (GP) with a distinctive structure that positively affects its dye adsorption efficiency. The variously formulated GP samples were tested for the removal of both methylene blue (MB-dye) and crystal violet dye (CV-dye) from an aqueous solution. The mathematical-statistical analysis of the experimental readings suggested that the generated special cubic models were significant, and thus the chosen approach was adequate for determining the optimum blending proportion. The optimization tools indicated that the optimal mixture from the three aluminosilicate precursors for developing a GP with high adsorption efficiency was 58% MK, 42% K, and 0% CFA. The optimized geopolymer (GPO) was synthesized and then analyzed using a variety of physicochemical techniques, which revealed the presence of an amorphous N-A-S-H gel-rich porous structure as an influencing property on the geopolymer's organic dye adsorption efficiency. The dependence of the adsorption mechanism of both MB-dye and CV-dye by GPO on the adsorbent dosage, contact time, initial dye concentration, temperature, and solution pH was evaluated. The isothermic and kinetic experimental readings for MB and CV-dyes adsorption by GPO were well fitted to the pseudo-second-order and Freundlich models, with an exothermic, favorable, and spontaneous adsorption reaction thermodynamically. The experimental studies in the lab scale on GPO produce comparable results. From these results, it has been concluded that the accuracy and feasibility of the mixture design simulation succeeded in optimizing and developing a geopolymeric sorbent material with great potential as an excellent economical agent for removing cationic dyes from aqueous media. This point represents an added value compared to traditional non-optimized geopolymer absorbents. Besides, this geopolymer material represents a significant application possibility for water treatment and remediation of hazardous dye pollutants.

Removal of Chromium (VI) from Aqueous Solution Using Activated Carbon Derived from Modified Bambara Nut Shells (Vignasubterranea (L.) verdc.)

Adsorption of Cr (VI) ions from aqueous solution using activated carbon derived from Bambara nut shells (BBNSAC) was investigated using batch adsorption technique. The maximum removal of Cr (VI) ions onto BBNSAC corresponding to 68.00 mg/g was achieved at pH 2, adsorbent dosage 0.01 g and contact time of 60 minute. The Equilibrium data of adsorption revealed that the adsorption of Cr (VI) ions showed better fitting to Langmuir isotherm in comparison to Freundlich, Temkin and Dubinin-Radaushkevich isotherm models. The value of Langmuir monolayer coverage was 55.56 mg/g. However, the kinetics of adsorption was best described by pseudo second-order model with highest correlation coefficient, R2 value of 0.984. Thermodynamics parameters of adsorption revealed negative value of Gibb’s free energy (∆G) indicating a feasible and spontaneous adsorption process whereas the positive value of change in enthalpy (∆H) indicates that the adsorption process was endothermic in nature while the positive value of change in entropy (∆S) revealed that there is an increase in randomness at solid-solution interface during adsorption process.

Bio-based and self-catalyzed waterborne polyurethanes as efficient corrosion inhibitors for sour oilfield environment

Sunflower oil was used as environmentally friendly source to develop novel self-catalyzed waterborne polyurethanes (WPUs) as efficient corrosion inhibitors for sour oilfield solution. A comprehensive experimental and computational analysis was performed to evaluate the inhibition effect of WPUs. The results of electrochemical measurements indicated that 200 µM of WPUs were effectively protected mild steel from sour corrosion by 95% and 94.6% at 25 °C and 60 °C, respectively. Furthermore, it was found that the best inhibition efficiency was provided by WPU when pyrrolidine was included in its structure, particularly at 60 °C. Additionally, a smoother steel surface was observed in the presence of WPUs, indicating the adsorption of the polyurethane molecules on the metal surface. The results of X-ray photoelectron spectroscopy further confirmed the chemical adsorption of WPUs on the surface of mild steel. Moreover, scanning Kelvin probe microscopy revealed that the potential distribution of the steel surface was shifted to the negative values, which show the adsorption of the inhibitor on the surface and inhibition of the corrosion process. Besides, high values of adsorption energy were achieved for WPUs using molecular dynamic simulation, indicating their spontaneous adsorption to the Fe (110) surface. The maximum adsorption energy of −794.9 kcal/mol was obtained for WPU3, which is consistent with experimental data. These results show that sunflower oil can be considered a potential source to develop self-catalyzed polyurethanes under mild conditions as effective corrosion inhibitors for sour environment.

Adsorption of textile dyes from aqueous solutions onto clay: Kinetic modelling and equilibrium isotherm analysis.

The commercial activated carbon commonly uses to reduce of dye amount in the textile industry effluents. In this study has focused on the use of a natural clay sample as low cost but potential adsorbent. For this purpose the adsorption of commercial textile dyes, Astrazon Red FBL and Astrazon Blue FGRL, onto clay was investigated. The physicochemical and topographic characteristics of natural clay sample were determined by scanning electron microscopy (SEM), X-Ray fluorescence spectrometry (XRF), X-Ray diffraction (XRD), thermogravimetric analysis (TGA), and cation exchange capacity measurements. It was determined that the major clay mineral was smectite with partial impurities. The effects of several operational parameters such as contact time, initial dye concentration, temperature, and adsorbent dosage on the adsorption process were evaluated. The adsorption kinetics was interpreted with pseudo-first order, pseudo-second order, and intra-particle diffusion models. The equilibrium adsorption data were analyzed using Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherm models. It was determined that the adsorption equilibrium was reached in the first 60min for each dye. The amount of adsorbed dyes onto clay decreased with increasing temperature, similarly, it decreased with increasing sorbent dosage. The kinetic data were well described by pseudo-second order kinetic model, and adsorption equilibrium data was followed both Langmuir and Redlich-Peterson models for each dyes. The adsorption enthalpy and entropy values were calculated as -10.7kJ.mol-1 and -13.21J.mol-1.K-1 for astrazon red and those for astrazon blue -11.65kJ.mol-1 and 37.4J.mol-1.K-1, respectively. The experimental results support that the physical interactions between clay particles and dye molecules have an important role for the spontaneous adsorption of textile dyes onto the clay. This study revealed that clay could effectively be used as an alternative adsorbent with high removal percentages of astrazon red and astrazon blue.

In situ boron-doped cellulose-based biochar for effective removal of neonicotinoids: Adsorption mechanism and safety evaluation

Biochar materials have been widely employed for adsorption of pollutants, which necessitates further consideration of their efficiency and safety in environmental remediation. In this study, a porous biochar (AC) was prepared through the combination of hydrothermal carbonization and in situ boron doping activation to effectively adsorb neonicotinoids. The adsorption process was shown to be a spontaneous endothermic physical adsorption process, where the predominant interaction forces between the acetamiprid and AC were electrostatic and hydrophobic interactions. The maximum adsorption capacity was 227.8 mg g−1for acetamiprid and the safety of AC was verified by simulating the situation where the aquatic organism (D. magna) was exposed to the combined system (AC & neonicotinoids). Interestingly, AC was observed to reduce the acute toxicity of neonicotinoids owing to the reduced bioavailability of acetamiprid in D. magna and the newly generated expression of cytochrome p450. Thus, it enhanced the metabolism and detoxification response in D. magna, which reducing the biological toxicity of acetamiprid. This study not only demonstrates the potential application of AC from a safety perspective, but also provides insight into the combined toxicity caused by biochar after adsorption of pollutants at the genomic level, which fills the gap in related research.

Adsorption of RhB dye on soy protein isolate-based double network spheres: Compromise between the removal efficiency and the mechanical strength

Soy protein isolate-based double network spheres (SPIDNS) were designed and adopted for the first time for Rhodamine B (RhB) dye removal from wastewater. The SPIDNS were prepared through the aziridine crosslinker and the Ca2+ ionic double crosslinking method with major crosslinking agents of soy protein isolate and sodium alginate, in which aziridine crosslinker was also employed as a modifier to regulate the mechanical strength. The physicochemical properties of the materials were explored by numerous technologies, including SEM NMR, FT-IR, and XPS, which confirmed the chemical and physical crosslinked networks of SPIDNS being established after aziridine crosslinker and Ca2+ ionic crosslinking process. Adsorption performances for RhB removal were investigated under various conditions by using SPIDNS with different dosages of aziridine crosslinker for 0%, 1.8%, 3.6%, 5.3%, 6.9%, and 8.5%. Experimental results demonstrated that the mechanical stability of the adsorbent was enhanced with increasing the amount of aziridine crosslinker from 0% to 8.5%; whereas, the adsorption capacity decreased from 190 to 120 mg/g. Therefore, a compromise between the removal efficiency and the mechanical strength should be taken into account. Studies of adsorption kinetics, isotherms, and thermodynamics displayed that the spontaneous RhB adsorption on SPIDNS was well described by a pseudo-second-order kinetic model and Langmuir isotherm model with monolayer adsorption behavior, for which both the correlation coefficients R2 were higher than 0.99. Moreover, electrostatic interactions between the positively charged RhB molecules and the negatively charged SPIDNS were proposed as the principal adsorption mechanism, which was confirmed by Zeta potential analysis. The good mechanical stability and spherical porous structure make the SPIDNS with reliability and potential for practical application.