Pseudo-second Order Rate Model Research Articles

Fabrication of date palm kernel biochar-sulfur (DPKB-S) for super adsorption of methylene blue dye from water

A novel form of biochar was created by dehydration of Date palm kernel with 85% sulfuric acid. It was examined how the newly produced biochar (DPKB-S) affected the aqueous solution's capacity to extract Methylene Blue (MB) dye. The prepared DPKB-S was categorized by BET, BJH, FT-IR, SEM, EDX, DSC, and TGA analyses. The ideal pH for the MB dye adsorption by DPKB-S is 8. With 0.75 g L−1 of DPKB-S and an initial concentration of 50 ppm MB dye, Date Palm Kernel Biochar-Sulfur (DPKB-S) had the highest removal percentage of 100%. The Langmuir and Freundlich isotherm models were used to investigate the collected data. Freundlich model is the model that best covers MB dye adsorption in DPKB-S at low concentrations (0.75–1.25 g L−1) and the Langmuir model at high concentrations (1.5–1.75 g L−1). The Langmuir model maximum adsorption capacity (Qm) of the DPKB-S was 1512.30 mg g−1. Furthermore, a variety of error function models were applied to investigate the isotherm models derived data, including Marquardt’s percent standard deviation (MPSD), the sum of absolute errors (EABS), the sum of the errors squared (ERRSQ), root mean square errors (RMS), Chi-square error (X2), the average relative error (ARE), average percent errors (APE), and hybrid error function (HYBRID). Kinetic data were calculated by intraparticle diffusion (IPD), pseudo-second-order (PSO), pseudo-first-order (PFO), and film diffusion (FD) models. A PSO rate model with a strong correlation (R2 = 1.00) largely regulated the adsorption rate. The removal mechanism of MB dye by DPKB-S is based on the principle that these positively charged dyes are attracted by electrostatic attraction forces due to the growth in the number of negatively charged regions at basic pH value. According to the results, DPKB-S shows promise as an affordable and competent adsorbent for the adsorption of MB dye. It can be used frequently without experiencing a discernible decrease in adsorption efficiency.

Removal of cesium and strontium ions with enhanced solid-liquid separation by combined ion exchange and BaSO4 co-precipitation

Treatment of cesium and strontium is critical in radioactive liquid waste management, where their ions are difficult to remove in single operations, owing to differences in valence state. Here, the efficacy of composite coagulants synthesised by combining fine clinoptilolite with co-precipitated barite (BaSO4) were investigated for the simultaneous removal of Cs+ and Sr2+ ions, producing aggregates with enhanced dewatering properties. Co-precipitated BaSO4 without clinoptilolite was found to be very effective in the removal of Sr2+ (>99 %) while only giving low-level Cs+ removal (~14 %) for solutions containing 25 ppm of Cs+ and Sr2. Conversely, pure clinoptilolite gave high Cs+ removal (>98 %) with rapid adsorption (<1 h) fitted to a Pseudo-Second Order (PSO) rate model. Composite coagulants were then produced using natural clinoptilolite combined with BaSO4 co-precipitation. Higher Sr2+ removal was obtained in all cases (>99.9 %), whereas Cs+ removal was reduced to <90 %, owing to exchange interactions with free Ba2+ ions. However, NaCl-preactivated clinoptilolite overcame low Cs+ removal efficiency, achieving >95 % removal. Their physical properties, sedimentation rates, and compressional yield stress were also studied to characterise the aggregates solid-liquid separation behaviour. The combined coagulates obtained settling rates almost twice that of pure BaSO4, and produced much greater consolidation, owing to increased aggregate density. Also, the combined systems had a higher gel point and lower specific compressive yield stress, suggesting less resistance to compression under centrifugal forces for dewatering. Overall, this study highlights that the use of composite coagulants can improve the removal efficiency of Cs+ and Sr2+ while also accelerating solid-liquid dewatering.

Selective recovery of Th(IV) from radioactive rare earth waste residue by utilizing MoS2-modified ion-absorbed type rare earth tailings

In the process of extracting ion-absorbed rare earth ore (IREO), the production of radioactive waste is a major environmental concern. To address this issue, MoS2 was used to modify ion-absorbed rare earth tailings (RET) to synthesize a novel MoS2@RET composite material for the effective handling of radioactive waste generated in IREO separation industry. The composite material was thoroughly characterized using various analytical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and energy dispersive spectroscopy (EDS). By optimizing the operating parameters, the optimal experimental conditions were determined to be pH = 3, contact time = 60 min, liquid-solid ratio = 6 g/L, and initial concentration = 150 mg/L. The adsorption data fitted well with the pseudo second-order rate model. The thermodynamic parameters concerning the adsorption of Th(IV) were analyzed and computed. Langmuir isotherm model is a more fitting choice for the adsorption process compared to the Freundlich isotherm model. MoS2@RET was used in the acid leachate of IREO waste residue, achieving the separation of Th and rare earth successfully. The mechanism of Th(IV) adsorption by MoS2@RET was investigated, revealing that the adsorption process involves electrostatic interactions, chemical bonding, and redox reactions. The above research results indicate that MoS2@RET composite materials have application potential in the sustainable treatment of IREO radioactive waste.

Dendrimer functionalized spinel ferrite for robust sorption of precious metals from strongly acidic medium

The separation of noble metal ions from strongly acidic solutions is considered to be a challenging task due to the significantly low pH of these solutions. Spinel ferrites possess unique physicochemical properties, such as excellent magnetic properties, high specific surface area, high chemical stability, active surface sites, and easy modification or functionalization, making them suitable for various applications. In this study, we have introduced a facile method for synthesizing polyamidoamine (PAMAM) dendrimer-functionalized spinel ferrite (DFSF) with a particle size of approximately 10 nm. The prepared DFSF materials have investigated its ability to adsorb Pt(IV) and Pd(II) anions (PtCl62− and PdCl42−) from strongly acidic solutions. The results indicate that the adsorption kinetics and isotherm studies of synthesized materials have a rapid and high adsorption capacity for Pt(IV) and Pd(II) with simple solid-liquid separation. The data analysis suggests an anion exchange interaction between the adsorbate and the adsorbent, specifically the electrostatic interaction between the protonated amine group (–NH3+) and the noble metal anions (PtCl62–and PdCl42−). The Pseudo second-order rate model fitting suggests that the adsorption of noble metals by DFSF is a function of valence. The excellent superparamagnetic properties (0.346 emu g−1) of DFSF make it a promising candidate for large-scale applications, as it exhibited good reusability with a short recovery time (25 s) and high recovery efficiency through the adsorption-reduction-precipitation route. This study suggests that DFSF can be a potential sorbent for noble metal ions in various applications.

Kinetic and isotherm studies of Acid Orange 7 dye absorption using sulphonated mandarin biochar treated with TETA

This study contributes to the current state of knowledge by highlighting the physical–chemical interactions between biochar and dyes. The removal of Acid Orange 7 (AO7) dye by a modified biochar obtained from the wastes of mandarin peels (MPs) has been investigated in this work. A dehydration procedure with 80% H2SO4 under reflux was applied to produce an innovative biochar from MPs and then boiled with H2O2 and followed by boiling with triethylenetetramine to make mandarin biochar-C-TETA (MBCT). FTIR, SEM, EDX, BJH, BET, TGA, and DTA analyses were applied to investigate the MBCT. FTIR analysis showed an additional peak that confirmed the addition of the NH2 group to the MBCT structure. An amorphous carbon structure was also confirmed by XRD analysis. The AO7 dye solution pH was proved to give the best absorption at pH 2.0. Significant removal of AO7 dye 99.07% using an initial concentration of 100 mg/L of AO7 dye and a 0.75 g/L MBCT. The Langmuir (LNR) and Freundlich (FRH) isotherm models investigated the experimental results. The LNR was best suited to handle the working MBCT data. The maximum adsorption capacity (Qm) calculated for the MBCT was 312.5 mg/g using 0.25 g/L of the MBCT. Kinetic studies were conducted using the intraparticle diffusion (IND), film diffusion (FD), pseudo-first-order (PFOR), and pseudo-second-order (PSOR) models. The absorption rate was calculated using the ultimate value of the linear regression coefficient (R2 > 0.99), and the PSOR rate model was found to ideally describe the absorption process. The point of zero charge (pHPZC) was found to be 10.17. The electrostatic attractive-forces between the sorbent surface positively charged sites and negatively charged anionic dye molecules were the primary mechanism of the MBCT sorption of the AO7 dye’s anion absorption. The results indicate that the manufactured MBCT adsorbent may be useful for removing the AO7 dye from wastewater. MBCT can be used repeatedly for up to six cycles without dropping its absorption efficiency.

Kinetic and thermodynamics study of heavy metal ions adsorption from aqueous solution using new resin 8-hydroxyquinoline-furfural-hydroquinone (HQFH).

Used in this study to prepare for the new cross linked polymer&#x0D; adsorption to remove heavy metals(Hg*’,Cd*’,Zn*?,Pb”) in aqueous&#x0D; solution . Using UV-Visible spectrophotometer technique to determine the&#x0D; amount of adsorption and factors affecting the adsorption of PH and the&#x0D; distribution coefficient and the effect of temperature and study the&#x0D; thermodynamic functions process. The results showed that the highest&#x0D; amount of adsorption was ion (Zn*), which was 98.9% , Pb**= 80.2%&#x0D; ,Cd=75.3% and Hg*=67.9%. The results the thermodynamic parameter&#x0D; showed that reaction exothermic and value of AG is spontaneous. The&#x0D; adsorption kinetic was found to follow pseudo-second order rate model,&#x0D; due to the high correlation coefficient(R’) and agreement between the&#x0D; experimental and calculated value of qe (mg/l). The results proved the&#x0D; applicability of isotherm Freundilch equation for adsorption coefficient&#x0D; higher than for Langmuir correlation equation.

Evaporation kinetics during containerless chemical synthesis of ZIF-8 in levitated droplets.

Zeolitic imidazolate framework-8 was synthesized in a containerless state via acoustic levitation. The cavitation effect of ultrasound affected the coordination connection of organic ligands in acoustically levitated droplets and they exhibited a conspicuous difference in the particle size distribution as compared with those under normal conditions. Herein, methanol was chosen as the solvent to investigate the influence of droplet evaporation on acoustic levitation synthesis. The kinetic parameters of droplet evaporation such as geometrical morphology transformation, concentration change and temperature evolution were measured for the levitation state. Surface evaporation resulted in the drastic deformation of the droplet during ZIF-8 synthesis and caused its vertical vibration and shape oscillation. The abrupt change of the levitation state aggravated the sound field effect on the containerless synthesis and caused a decrease of particle size distribution. A two-dimensional axis-symmetry model was used to visually simulate the sound field distribution during acoustic levitation synthesis based on the finite element method. The fabricated ZIF-8 was able to remove phthalic acid in wastewater through adsorption, and its kinetic features followed a pseudo second-order rate model.

Mandarin Biochar-TETA (MBT) prepared from Citrus reticulata peels for adsorption of Acid Yellow 11 dye from water

Dehydration technique with 80% sulfuric acid was used to create a novel biochar from mandarin peel wastes followed by condensate with triethylenetetramine (TETA) to give Mandarin Biochar-TETA (MBT). BJH, BET, FTIR, SEM, DSC, TGA, and EDX studies were used to characterise the MBT. The capacity of the newly developed biochar to remove Acid Yellow 11 (AY11) dye from a water solution was studied. The pH of AY11 dye adsorption was found to be best at pH 1.5. Using 100 ppm AY11 dye as a beginning concentration and 1.75 g L–1 MBT dose, the greatest percent of AY11 dye removal by MBT was 97.83%. The MBT calculated maximum adsorption capacity (Qm) was 384.62 mg g–1. Langmuir (LIM), Freundlich (FIM), Tempkin (TIM), and Dubinin–Radushkevich (DRIM) isotherm models were applied to analyse the experimental data. Furthermore, the results of these isotherm models were investigated by various known error function equations. The MBT experimental data was best suited by the LIM. Pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich kinetic model (EKM), intraparticle diffusion (IPD), and film diffusion (FD) models were used to calculate kinetic data. A PSO rate model with a high correlation (R2 > 0.990) was used to assess the adsorption rate. The main mechanism of the MBT adsorption method of the AY11 dye’s anions adsorption is the electrostatic attractive forces that arise with the increase of positively charged sites in an acidic medium. The obtained data suggest that the prepared MBT adsorbent has the potential to be an effective material to remove the AY11 dye from water and that it may be used repeatedly without losing its adsorption efficiency.

Interaction Influence of Contact Time and pH on Cobalt Retention by Carbon Nanotubes Bearing Various Loads of TiO2 and Fe3O4

&lt;P&gt;Background: Nanomaterials have facilitated remarkable advances in the remediation of many environmental problems. A few studies have tackled the removal of Co (II) from aqueous solutions using nanomaterials. Herein, we studied the retention kinetics of cobalt species on carbon nanotubes (CNTs) bearing different amounts of TiO2 and Fe3O4 nanomaterials individually. &lt;P&gt; Methods: CNTs and their TiO2/Fe3O4-modified nanomaterials were well characterized. Cobalt retention by these adsorbents was investigated considering different influencing factors such as Co (II) content, solution pH, and time. The kinetic data were fitted with pseudo-first-order, pseudosecond- order rate models, and intra-particle diffusion models for better elucidation of the mechanism of Co retention. &lt;P&gt; Results: XRD evidenced the formation of TiO2 and Fe3O4. High loads of both oxides were needed for higher and faster Co retention by CNTs. Co retention capacity increased with increasing the solution pH. The pseudo-second-order model presented the kinetics of Co retention at 30 oC, and 48% of available capacity was attained within the first hour of interaction by CNT-TiO2 and with a moderate S/L ratio of 0.5 g/L. Co retention was increased with the amount of oxide to reach a maximum value of 16. 40 mg/g (90.2% TiO2) and 13.60 mg/g (48.2% Fe3O4). The Jovanović equilibrium model predicted the maximum retention values as the nearest to the experimental ones. &lt;P&gt; Conclusion: The potential of CNT-Fe3O4/TiO2 nanomaterials has been successfully demonstrated for the removal of cobalt, which makes them highly attractive and cost-effective adsorbents for wastewater treatment. The reported retention and removal rate values were relatively better than those seen in the literature. Loading different active oxides by CNTs is an interesting research area as selective adsorbents can be fabricated with affordable experimental costs.

Synthesis of a tertiary amine hydrochloride macroporous resin adsorbent for removal of oxyhalide anions from water: Performance, adsorption mechanism, and toxicity

The non-volatility, high solubility, and chemical stability of oxyhalide anions make them difficult to remove from waters. Here we describe the synthesis and characterization of tertiary amine hydrochloride macroporous resins (TAHMR) that show excellent performance for the adsorption of oxyhalide anions. Adsorption capacities were in the order ClO4− > ClO3− > ClO2− > BrO3−, and compared favorably with those from various commercial resins studied. Compared with the common anions in water, TAHMR has better selectivity for ClO4−. Adsorption of ClO4− on TAHMR increased with increasing pH in the range 2.0–4.0, but was independent of pH in the range 4.0–10.0, and was only slightly affected by the presence of HCO3− and HPO42−. The adsorption kinetics followed the pseudo-second order rate model and was fitted well by the Langmuir isotherm with maximum adsorption capacity of 2.74 mmol g−1. Investigations with various spectroscopic techniques and quantum chemistry calculations indicate that adsorption of oxyhalide anions occurs at the nitrogen atoms in the resin. Furthermore, TAHMR resins could be effectively regenerated and reused, and did not show any cytotoxic effects. Thus, TAHMR is a promising adsorbent for practical application in the removal of oxyhalide anions from water.

Biochar-SO prepared from pea peels by dehydration with sulfuric acid improves the adsorption of Cr6+ from water

A new biochar was produced from pea peel residues by the dehydration process. The effect of the obtained new biochar on the ability to remove Cr6+ ions from the aqueous solution was investigated. Biochar-SO was obtained from pea peel by dehydration of biochar with 50% sulfuric acid. The obtained biochars were characterized by Fourier transform infrared (FT-IR); Brunauer, Emmett and Teller (BET); Barrett-Joyner-Halenda (BJH); thermogravimetric analysis (TGA); differential scanning calorimetry (DSC); scanning electron microscope (SEM); and energy-dispersive X-ray (EDAX) analyses. The optimum pH value for Cr6+ ion removal was determined as 1.48. The maximum removal percentage of Cr6+ ions was 90.74% for Biochar-SO of 100 mg·L−1 Cr6+ ions initial concentration and 1.0 g L−1 adsorbent dosage. The maximum adsorption capacity (Qm) of biochar-SO was 158.73 mg·g−1. The data obtained were analyzed with Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. In addition, the data obtained from these isotherm models were tested using different error functions (hybrid error function (HYBRID), average percent errors (APE), the sum of the absolute errors (EABS), chi-square error (X2), and Marquardt’s percent standard deviation (MPSD and the root mean square errors (RMS)) equations. It was the Freundlich isotherm model that best fits the experimental data of biochar-SO. Kinetic data were evaluated by pseudo–first-order (PFO), pseudo–second-order (PSO), Elovich, and intraparticle diffusion models. The adsorption rate was primarily controlled by the PSO rate model with a good correlation (R2 = 1). The adsorption mechanism of biochar-SO to remove Cr6+ ions can be based on electrostatic interaction and ion exchange with exchangeable cations in biochar such as aluminum, silicon, and calcium ions for chromium. The results indicate that biochar-SO is a promising adsorbent for the adsorption of Cr6+ ions that can be employed repeatedly without substantial loss of adsorption effectiveness.

Bimetallic Fe/Ni nanoparticles derived from green synthesis for the removal of arsenic (V) in mine wastewater

Since the incidences of arsenicosis have significantly increased worldwide in the last decade, remediation of arsenic (As) pollution is now imperative. In this study, calcined green synthesized Fe/Ni nanoparticles (C–Fe/Ni NPs) were evaluated for their efficacy for As (V) removal from aqueous solution. Under optimal experimental conditions As (V) removal efficiency reached 87.3%. Analysis of changes in the surface properties of C–Fe/Ni NPs before and after interaction with As (Ⅴ) using a range of advanced characterization techniques including IC-AFS, SEM-EDS, XPS and XRD revealed that the As removal mechanism involved only adsorption. Adsorption kinetics followed a pseudo-second order rate model (R2 > 0.986) and adsorption best fit the Langmuir isotherm model (R2 > 0.958). Thermodynamic studies indicated that adsorption was a spontaneous endothermic process. On the basis of these results, a removal mechanism of As (Ⅴ) by C–Fe/Ni NPs was proposed. Finally, the efficacy of the material for practical remediation of As from aqueous solution was assessed, including the influence of coexisting anions. While Cl−, NO3− and SO42− had little influence on As (V) removal, both H2PO4− and HCO3− significantly negatively affected removal.

Preparation and recycled simultaneous adsorption of methylene blue and Cu2+ co-pollutants over carbon layer encapsulated Fe3O4 /graphene oxide nanocomposites rich in amino and thiol groups

To find an efficient material to simultaneously remove the co-existed ionic dyes and toxic metal ions, in this paper, carbon layer encapsulated Fe 3 O 4 /graphene oxide nanocomposites rich in amino and thiol groups (Fe 3 O 4 @C /GO) was fabricated. With methylene blue (MB) and Cu 2+ as two different models of pollutants, the effects of time, initial concentration, pH values, and adsorbent dosage on the adsorption capacity of GO/ Fe 3 O 4 @C were conducted, respectively. A pseudo-second order rate model best simulated the kinetic adsorption process for both MB and Cu 2+ among the pseudo-first order, pseudo-second order, and Weber and Morris intra-particle diffusion models. The adsorption data were better fitted with the Langmuir adsorption isotherm model than Freundlich equation for both MB and Cu 2+ adsorption. The monolayer adsorption capacities analyzed from Langmuir model were 116.50 mg . g −1 and 76.86 mg . g −1 for MB and Cu 2+ , respectively. In MB- Cu 2+ binary system, resulted from the smaller separation factor (S F ) value of MB than Cu 2+ , MB had a suppression effect on Cu 2+ ions binding during the simultaneous adsorption process. But for the MB simultaneous adsorption and preloading, the impact of Cu 2+ ions on the MB adsorption capacity was almost negligible. Besides these important results, the easily magnetically separation and good regeneration property of Fe 3 O 4 @C /GO further indicated a kind of stable and efficient adsorbent with great potential in sewage treatment, while being very adaptable when compared with other magnetic carbon-based adsorbents. To find an efficient material to simultaneously remove the co-existed ionic dyes and toxic metal ions, carbon layer encapsulated Fe 3 O 4 /graphene oxide nanocomposites rich in amino and thiol groups were designed and synthesized as an adsorbent for recycled simultaneous removal of methylene blue (MB) and Cu 2+ co-pollutants, as well as the studies on parameters affecting adsorption capacity, kinetic, thermodynamic and mechanisms analysis. • Fe 3 O 4 @C /graphene oxide nanocomposites with amino/thiol-rich groups were fabricated. • The nanocomposites can simultaneously remove MB and Cu 2+ with a high efficiency. • Equilibrium data were well fitted by the Langmuir model for both MB and Cu 2+ . • A pseudo-second order rate model best simulated the kinetic adsorption process. • Suppression adsorption for Cu 2+ by MB was observed in the simultaneous adsorption process.

Coagulated Mineral Adsorbents for Dye Removal, and Their Process Intensification Using an Agitated Tubular Reactor (ATR)

The aim of this study was to understand the efficacy of widely available minerals as dual-function adsorbers and weighter materials, for the removal of toxic azo-type textile dyes when combined with coprecipitation processes. Specifically, the adsorption of an anionic direct dye was measured on various mineral types with and without the secondary coagulation of iron hydroxide (‘FeOOH’) in both a bench-scale stirred tank, as well as an innovative agitated tubular reactor (ATR). Talc, calcite and modified bentonite were all able to remove 90–95% of the dye at 100 and 200 ppm concentrations, where the kinetics were fitted to a pseudo second-order rate model and adsorption was rapid (&lt;30 min). Physical characterisation of the composite mineral-FeOOH sludges was also completed through particle size and sedimentation measurements, as well as elemental scanning electron microscopy to determine the homogeneity of the minerals in the coagulated structure. Removal of &gt;99% of the dye was achieved for all the coagulated systems, where additionally, they produced significantly enhanced settling rates and bed compression. The greatest settling rate (9 mm min−1) and solids content increase (450% w/w) were observed for the calcium carbonate system, which also displayed the most homogenous distribution. This system was selected for scale-up and benchmarking in the ATR. Dye removal and sediment dispersion in the ATR were enhanced with respect to the bench scale tests, although lower settling rates were observed due to the relatively high shear rate of the agitator. Overall, results highlight the applicability of these cost-effective minerals as both dye adsorbers and sludge separation modifiers to accelerate settling and compression in textile water treatment. Additionally, the work indicates the suitability of the ATR as a flexible, modular alternative to traditional stirred tank reactors.

Multidentate thia-crown ethers as hyper-crosslinked macroporous adsorbent resins for the efficient Pd/Pt recovery and separation from highly acidic spent automotive catalyst leachate

Multidentate thia-crown ether (CE) diols containing different number of sulfur heteroatoms (2S-4S) were developed as ligands for Pd and Pt. Seven thia-CE diols (denoted as: 2g-2m) were synthesized at 63–93% yields through ring-opening cyclization of bis-epoxide intermediates with 1,2-benzenedithiol. Each thia-CE contains 2 –OH groups as reactive sites for adsorbent fabrication. Initial screening of thia-CE diols through liquid–liquid extraction and density functional theory (DFT) calculations reveal that bidentate (2S, 2O) dithia-CE diol 2i with cavity size Ø2i = 1.61 Å is most selective towards Pd (ØPd2+=1.56 Å) and tetradentate (4S) tetrathia-CE diol 2m (Ø2m = 1.57 Å) to Pt (ØPt2+=1.48 Å). DFT calculations indicate that size-match relationship and denticity difference dictated the coordination stability of 2i with Pd and 2m with Pt, which ultimately defined their respective selectivities. Thia-CEs 2i and 2m were subsequently fabricated as macroporous adsorbent resins (2i-X and 2m-X) via crosslinking of their bis-epoxide derivatives with ethylenediamine in porogenic PEG 400 solvent. Metal ion uptakes were Langmuir-type with high capacities (2i-X: QPd = 212 mg g−1; 2m-X: QPt = 345 mg g−1) and kinetic rates follow the pseudo-second order rate model. Metal ion uptakes are mainly due to neutral coordination with the thia-CEs (84–86%) and to some extent, due to anion complexation with ammonium groups (14–16%). Recovery of Pd by 2i-X and Pt by 2m-X can be carried out effectively and repeatedly in highly acidic feed (6 M HCl) without performance deterioration. Sequential adsorption of Pd by 2i-X and Pt by 2m-X are highly selective in the presence of base metal ions (Mg2+, Al3+, Cr3+, Mn2+, Fe3+, Ni2+, and Pb2+) making these resins ideal for the treatment of highly acidic spent auto-catalyst leachate.

Novel magnetic gel composite based on sodium alginate crosslinked by Yttrium(III) as biosorbent for efficient removal of direct dyes from aqueous solution

A novel magnetic gel composite Fe3O4@SA/Y was synthesized by synergistic cross-linking reaction of sodium alginate (SA) and Yttrium(III) ions with Fe3O4 and characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Fourier Transform-Infrared (FTIR), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and BET specific surface area test method, respectively. The magnetic composite was used for the removal of three dyes, Direct Blue 86 (DB-86), Direct Green 6 (DG-6) and Direct Brown 2 (DB-2) from water. Batch adsorption studies show that the ultra-high removal efficiency of 98.8, 97.2 and 95.6% for DB-86, DG-6 and DB-2 adsorption onto Fe3O4@SA/Y in 120 min of contact time at pH 2.0 decreases slightly with the pH increase from 2.0 to 10.0 at 298 K. The adsorption process of each dye completely accords with the pseudo-second order rate model. Equilibrium data of DB-86 conform to the Langmuir model well, while the adsorption behavior of DG-6 and DB-2 can be better described by the Freundlich model. The saturated adsorption capacity can reach 370, 435 and 1250 mg/g for DB-86, DG-6 and DB-2 at 328 K, respectively. The thermodynamic studies revealed the spontaneous and endothermic nature of adsorption reaction. The dye adsorption by Fe3O4@SA/Y mainly involved electrostatic adsorption, hydrogen bonding and complexation. An eco-friendly Fe3O4@SA/Y biosorbent with high-cost performance and easy separation through magnetic properties has promising application for the efficient removal of dark color for dye effluent with a very wide pH range.

Application of a novel nanocomposites carbon nanotubes functionalized with mesoporous silica-nitrenium ions (CNT-MS-N) in nitrate removal: Optimizations and nonlinear and linear regression analysis

Abstract In recent years, the increase in the use of agricultural fertilizers in industrial development has produced poisonous inorganic ions such as nitrates in water and soil. Nitrates in drinking water which may come from nitrogen fertilizers are a potential health risk. Removal of nitrates from the environment is a big challenge. Following the series of investigation, the present study proposes the multiwall carbon nanotubes functionalized with mesoporous silica-nitrenium ions (CNT-MS-N) as a novel adsorbent for removing nitrate ions (NO 3 − ) from aqueous solution. The ability of CNT-MS-N to remove nitrate ions from aqueous solutions was studied at different operating conditions. The maximum removal (98%) was obtained under the optimum conditions: adsorbent dosage of 70 mg and pH 7 and for initial concentration of 80 (ppm) at 30 °C for 5 h contact time. FTIR spectroscopy showed the contribution of amine, amide groups in removing nitrate and the FESEM-EDX results confirmed the adsorption of nitrate ions on the function groups of CNT-MS-N. In addition, nonlinear and linear isotherms and kinetics models were used to evaluate the equilibrium adsorption results. The coefficient of determination (R2) was used to determine the best-fit model expected by each approach. The results showed that the non-linear Langmuir isotherm model is a better way to achieve adsorption parameters illustrating the adsorption of nitrate ions onto CNT-MS-N with R2 (0.9829). Likewise, it was found that the nonlinear Pseudo-second order rate model using the non-linear regression approach better predicted experimental results with R2 (0.9921). The present investigation confirmed the nonlinear method as an appropriate technique to predict the optimum adsorption isotherm and kinetic data.

Hydrothermally synthesized MnO2 nanowires and their application in Lead (II) and Copper (II) batch adsorption

Manganese oxide (MnO2) nanowires with diameters of 20 nm to 100 nm are synthesized by hydrothermal method. Chemical characterization of these nanostructures demonstrates the formation of Mn(IV), corroborating the MnO2 compound. The nanowires were used as adsorbents of Pb(II) and Cu(II) ions from water in batch system at room temperature. The results indicate faster adsorption rates and better affinity towards Pb(II) compared to Cu(II), since the adsorption capacity (3.730 [mg·g−1]) and the percentage of removal (99.99%) at equilibrium for Pb(II) are higher than those for Cu(II), 2.972 [mg·g−1] and 75.48%. The kinetics of adsorption was described by a pseudo-second order rate model for both ions, and Weber and Morris intra-particle diffusion model was used to a better understanding of the process. In addition, the Langmuir and Freundlich models were used to describe the isotherms, the first model was better adjusted for Cu(II) adsorption and the later for Pb(II) adsorption.

Removal of Cd(II) from water using zero valent iron/copper functionalized spent tea.

Zero valent Fe/Cu functionalized spent tea adsorbent was prepared for the decontamination of Cd(II) contaminated water. The synthesized material was characterized for structural and morphological characteristics using various analytical techniques. The material was used as adsorbent for the adsorption of Cd(II) from aqueous solutions in batch study experiments. The effect of initial pH, adsorbent dosage, contact time and adsorbate concentration was investigated. The obtained data well followed the Langmuir adsorption isotherm model and pseudo-second order rate model with maximum adsorption capacity of 89.686 mg·g-1. Based on Langmuir separation factor (R), having a value of 0.706-0.194, the adsorption process was confirmed to be favorable. The adsorbent was used in the form of a column for the sorption of Cd(II) from a running solution with satisfactory results. The spent material was regenerated and reutilized with reduction of adsorption capacity by 1.48% only. Overall, the current adsorbent can be efficiently utilized for the removal of aqueous Cd(II).

Uranium concentration using reactive polymer thin films for spectroscopic analyses

This contribution describes the development of reactive polymer films for the concentration of uranium from circumneutral pH solutions for spectroscopic analyses. These films were prepared by grafting uranium-selective polymers from polyethersulfone (PES) films via UV-initiated polymerization, and by introducing uranium-selective functional groups to polyacrylonitrile (PAN) films by chemical reaction. Ellipsometry was used to study poly(phosphoric acid 2-hydroxyethyl methacrylate ester) film growth kinetics on PES films. X-ray photoelectron spectroscopy of modified PAN films revealed conversion of nitrile groups to amidoxime groups to be as high as 40% and showed that the extent and depth of reaction could be varied precisely. Static uptake experiments with solutions of depleted uranium spiked with 233U were conducted to determine uranium binding capacities and kinetics of the modified polymer films at different pH values from 4 to 8. Sorption isotherm data were fitted to the Langmuir model, and the highest sorption capacities of 1.09 × 10−2 ± 1.03 × 10−3 mmol m−2 and 1.02 × 10−2 ± 3.00 × 10−3 mmol m−2 were obtained at pH 6 for modified PAN (M-PAN) and PES (M-PES) films. Capacities at pH 4 and 8 were lower and could be explained by differences in sorption mechanisms. Uranium batch uptake kinetics followed a pseudo-second order rate model. Equilibrium uptake was attained within 3 h for M-PAN film and 1 h for M-PES film. Alpha spectroscopy pulse height spectra were analyzed to study the role of selective layer film thickness on peak energy resolution. Full width at half maximum values from 29 to 41 keV were recorded for M-PAN film and from 26 to 45 keV for M-PES film. Whereas uranium uptake increased with selective layer film thickness and varied with polymer chemistry/extent of modification, the peak energy resolution was independent of layer thickness and polymer chemistry within the experimental measurement uncertainties. Results from this work are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of radionuclides in water for nuclear forensics investigations and environmental studies.