Desorption Reagent Research Articles

Efficient and rapid capture of uranium(VI) in wastewater via multi-amine modified β-cyclodextrin porous polymer

Efficient and rapid capture of uranium(VI) in wastewater via multi-amine modified β-cyclodextrin porous polymer

Reduced graphene oxide-zinc iron oxide nanomaterial as selective dispersive solid-phase extraction sorbent for extraction and enrichment of aflatoxins from milk combined with UHPLC-MS/MS analysis

Fungal species capable of producing aflatoxins frequently contaminate the feed provided to dairy animals, leading to the subsequent occurrence of aflatoxin contamination in milk. Milk is renowned for its exceptional nutritional composition, and the consumption of milk contaminated with aflatoxins by humans can engender a multitude of health complications. In this study, reduced graphene oxide zinc iron oxide (rGO-Zn/Fe2O4) nanomaterial was utilized as a dispersive solid phase extraction adsorbent to separate and enrich aflatoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, and aflatoxin M1) from milk. The rGO-Zn/Fe2O4 nanomaterial was morphologically characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, indicating that Zn/Fe2O4 nanoparticles were embedded on the surface of rGO. The acetonitrile/formic acid (99/1, v/v) combined with ultrasonic treatment for a duration of 40 min expressed an efficient extraction solvent. Employing the matrix-spiked technique, different parameters of the dispersive solid-phase extraction (d-SPE) method were meticulously optimized, yielding the following conditions: 2% acetonitrile as loading solvent, 15 mg of rGO-Zn/Fe2O4 as the adsorbent quantity, 15 min of ultrasonication as adsorption time, and n-hexane as the washing solvent. The desorption reagent was 5 mL acetonitrile, with a desorption time of 5 min. The combination of the dispersive solid-phase extraction (d-SPE) technique with validated UHPLC-MS/MS quantitative analysis demonstrated excellent selectivity, a robust linear relationship (R2 ≥ 0.994), remarkable sensitivity (limit of quantification ranging from 0.006 to 0.013 µg/L), and satisfactory recovery rates of 78%–104% at three different matrix-spiked levels. Moreover, the method exhibited precision with relative standard deviations (RSD) ranging from 2.4% to 10.8%. Following appropriate pretreatment procedures, the milk samples underwent rigorous aflatoxin analysis, leading to the identification of AFM1 presence in all of the examined milk samples (n = 9). However, the contamination levels detected were found to be within the permissible limits as defined by regulatory standards.

Enhanced Effectiveness on Phenol Removal by MgCr-LDH/Microcrystalline Cellulose Composite and Regeneration Study with Green Desorption Reagent

Modified MgCr-LDH with microcrystalline cellulose (MgCr/MCC) was successfully prepared by the coprecipitation method and characterized using XRD, FT-IR, and BET analyses. MgCr/MCC showed an increase in surface area from 21.51 to 26.056 m2/g. The material was tested as an adsorbent for the removal of phenol. MgCr/MCC showed an increase in adsorption capacity from the initial material of 24.631 to 58.480 mg/g. The optimum pH was at pH 9 and the adsorption process’s equilibrium time is 70 minutes. The correlation coefficients on the kinetics and isotherm parameters show that phenol removal follows the pseudo second order (PSO) and Langmuir models with spontaneous and endothermic adsorption processes. The regeneration ability of MgCr/MCC material using the water-assisted ultrasonic system as a green desorption reagent was 3 cycles with a percent regeneration efficiency of 39.45%.

Utilization of Sugar Beet Pulp as Biosorbent for Molassigenic Metal Ions: Kinetic Study of Batch Biosorption

The sugar industry is facing problems with high amount of molassigenic metal ions remained after the purification step in sugar juice. In this investigation the application of unmodified sugar beet pulp as a weak monofunctional cation-exchange biosorbent for molassigenic metal ions (Na+, K+ and Ca2+) removal from the alkalized sugar juice was studied. The batch biosorption experiments were performed at temperature (70 °C) and pH (10.5) of alkalized sugar juice similar to industrial conditions. The highest removal efficiency was noticed for divalent Ca2+ (30.2%), while monovalent Na+ and K+ ions were removed with 10.9 and 9.1% efficiency, respectively. Biosorption equilibrium was established in 90 min for all tested metals. Sugar beet pulp characterization from the perspective of cation-exhange material was conducted. The structure of the biosorbent and an insight of the functional groups were also characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The biosorption data were analyzed using four non-linear kinetic (pseudo-first order, pseudo-second order and Elovich) and diffusion models (Weber-Morris). The time course data of biosorption processes fitted well to the pseudo-first and the pseudo-second-order kinetic models indicating ion-exchange and chemisorption as dominant mechanisms for metal ions removal from the alkalized juice. HNO3 as a desorption reagent showed the highest average molassigenic metal ions desorption efficiency (54.4%). Utilization of sugar beet biomass as cation-exchange material imposes as a potential solution for more successful sugar juice purification.

High Selectivity and Adsorption Capacity for Congo Red Toward Anionic Dyes by Adsorbent: Modified LDH with Hydrochar Made from Nephelium Lappaceum Peel

<p>Synthesis of Ni/Al-LDH prepared into Ni/Al-Hc composites using hydrochar from rambutan peel (Hc) and applied as a congo red adsorbent and analyzed based on adsorption selectivity, kinetics, isotherms, adsorption thermodynamics and recycling. The success of Ni/Al-Hc composite preparation was proven by XRD, FT-IR, and BET analysis which showed the unique characteristics of Ni/Al and Hc. The results of the analysis of adsorbent characterization using XRD showed that the peaks in the Ni/Al-Hc composite were similar to typical peaks of Ni/Al appearing around 10.9°(003), 45.5°(018) and hydrochar appearing around 22°(002). The results of the analysis were strengthened by characterization using FT-IR which showed that the Ni/Al-Hc composite had similar spectra with the precursor. BET analysis showed that the Ni/Al-Hc composite had an increase in specific surface area to 11.879 m2/g from 5.845 m2/g after Ni/Al was composited with Hc. The adsorption study showed that the Ni/Al-Hc composite showed selective ability to congo red, and was in equilibrium at 100 minutes with a tendency for adsorption to follow pseudo first order (R2 is closer to 1). The adsorption isotherm shows that the adsorption of Congo red tends to follow Freudlich with the maximum adsorption capacity reaching qm (adsorption capacity) of 246.23 mg/g each using Ni/Al-Hc adsorbent and the adsorption process takes place by physisorption, spontaneous and endothermic. The adsorption regeneration ability is more stable up to the fourth cycle compared to Ni/Al-LDH and Hc with the best desorption reagent using hydrochloric acid.</p>

Novel nanometer silica desorption reagent reducing the damage of hydroxypropyl guar gum to sandstone reservoir

To improve the stimulation effect of sandstone reservoirs, NSDR is used to reduce the adsorption damage of hydroxypropyl guar gum fracturing fluid to sandstone the throats of sandstone. The adsorption capacity of guar gum in porous sandstone media is measured by an ultraviolet spectrophotometer. The effect of the nanometer silica desorption reagent (NSDR) on reducing adsorption damage was evaluated by displacement experiment combined with nuclear magnetic resonance, and the effects of temperature and residence time on the properties of NSDR were studied. The mechanism of reducing adsorption damage of NSDR was verified by X-ray electron spectroscopy and scanning electron microscope. The results show that NSDR can destroy the adsorption force between guar gum and rock and occupy the adsorption site on the rock surface, thus reducing the adsorption retention of HPG in sandstone porous media, reducing permeability damage, and improving pore throat structure. The temperature has little effect on the adsorbing properties of NSDR. The effect of NSDR is better after the residence time exceeds 240 min, and the longer the residence time, the better the effect. The addition of NSDR can effectively reduce the viscosity and surface tension of the gel breaker, and does not affect the rheological properties and gel breaking performance of the fracturing fluid. The field application results show that compared with the adjacent wells, the single well production of the NSDR application well increases obviously, and the cumulative production increases by 2.1 times after 100 days.

Effects of Chelating Surfactants on Competitive Adsorption of Lead and Zinc on Loess Soil

The study of competitive adsorption of heavy metals on soil is important for heavy metals contaminated soil remediation. However, there have been few studies on the impact of desorption reagents on heavy metal adsorption in soil. Batch adsorption studies were used to investigate the competitive adsorption mechanism of two heavy metals, Pb and Zn, on a loess soil in the presence of a new chelating surfactant, sodium N-lauroyl ethylenediamine triacetate (LED3A). Results showed that competitive adsorption equilibria of Pb and Zn were reached at 3 and 10 h, respectively. The maximum equilibrium adsorption capacities were 19.55 and 18.35 g.kg-1, respectively. LED3A affected the competitive adsorption kinetics of Pb and Zn by increasing the change in external mass transfer and reducing the change in internal mass transfer. LED3A reduced Pb and Zn adsorption capacities onto the soil through competitive chelation of the heavy metals. The heavy metal chelating ability of LED3A was higher for Zn than for Pb. When its concentration was larger than 5 g.L-1, LED3A showed a significant effect on the competitive adsorption of Pb and Zn. In the competitive system, the effect of Pb concentration on the Zn adsorption capacity was greater than the effect of Zn concentration on the Pb adsorption capacity. LED3A weakened the effect of Pb concentration and enhanced the effect of Zn concentration. LED3A showed a significant potential for efficiently leaching remediation of Pb and Zn co-contaminated soil.

Valorization of lemon peel waste as biosorbent for the simultaneous removal of nickel and cadmium from industrial effluents

The valorization of agricultural waste as biosorbent requires studies dealing with aqueous systems containing coexisting heavy metals. Batch adsorption experiments were carried out to study the competitive biosorption of Ni(II) and Cd(II) on alkali-modified lemon peel. The biosorption kinetic analysis indicated that the uptake of Ni(II) on lemon peel was better described by pseudo first-order model whereas for Cd(II) results were no conclusive. A rapid uptake of both metals on alkali-modified lemon peel was detected during the first 10 min obtaining more than 90% of the maximum sorption. The maximum adsorption capacity of Ni(II) and Cd(II) for single metal systems at optimum conditions (pH = 5, S/L = 5 g L−1, 25 ∘̲C), which were obtained from Langmuir model, reached as high as about 0.626 and 0.726 mmol g−1, respectively. These values were reduced 30 and 20 % in the presence of 100 mg L−1 of Cd and Ni, respectively. Regarding the reusability of the biosorbent, after five consecutives adsorption–desorption cycles using HNO3 and H2SO4 as desorption reagents percentages of 90 and 70 % were recovered for Ni and Cd. The promising results obtained through this work are expected to promote the use of lemon peel as an efficient biosorbent for industrial applications.

Environmentally friendly Pd(II) recovery from spent automotive catalysts using resins impregnated with a pincer-type extractant

Extractant-impregnated resins have potential for recovering platinum group metals selectively and efficiently. Herein, 1,3-bis(2-(octylthio)propan-2-yl)benzene (1), a pincer-type extractant, was impregnated in Amberlite XAD-7 resin (1-EIR), and the batch Pd(II) sorption conditions, including impregnated amount, shaking time, Pd(II) concentration, HCl concentration, and Pd(II) desorption reagents, were optimized. The maximum Pd(II) sorption capacity of 1-EIR was 49 mg g−1 after 24 h in a 700 ppm Pd(II) solution. Over 20 adsorption–desorption cycles, 1-EIR showed good reusability, with a sorption percentage (S%) of > 92%. However, not all Pd(II) was desorbed from 1-EIR. Complete Pd(II) collection was achieved by combining desorption with flaking of the Pd–extractant complex from Pd(II)-loaded 1-EIR by Soxhlet extraction, as ~ 13 mg g−1 remained after the 20th adsorption–desorption cycle by absorptiometric method. The sorption mechanism was elucidated based on the Langmuir isotherm model, thermodynamic parameters, and sorption kinetics. Pd(II) sorption by 1-EIR was spontaneous and endothermic, and the sorption kinetics followed a pseudo-second-order model. Notably, 1-EIR also exhibited high selectivity for Pd(II) from a simulated mixed metal solution and a spent automotive catalyst leachate (S% = 98% and > 99%, respectively). Thus, this extractant-impregnated system is promising for selective Pd(II) recovery from spent automotive catalysts and other secondary resources.

Removal of Cu(II) from Water by a Novel Graphene Oxide/Hexadecyltrimethylammonium Composite Sponge and Its Regeneration for Reuse

Graphene oxide has great potential for use as an adsorbent due to the high specific surface area, high negative charges, and abundant oxygen-containing functional groups. However, the difficulty of graphene oxide to separate from water renders it impractical for real water treatment. In the present study, a novel graphene oxide/hexadecyltrimethylammonium composite sponge (GO/HDTMA) was prepared and investigated for use as a filtration material for the removal of Cu(II) from water. The formed porous GO/HDTMA sponge was highly stable in water. The adsorption was spontaneous and exothermic, increasing with decreasing temperatures. The material showed good ability to remove Cu(II) with competing cations (K+, Na+, Ca2+, and Mg2+) present. Five cycles of adsorption-desorption-regeneration studies showed that, after adsorption, the material could be successfully regenerated for repeated use by using a 1-M HCl solution as the desorption reagent. At a sufficiently high dose, GO/HDTMA showed an excellent performance for Cu(II) removal from river water containing different coexisting solutes. Finally, our 30-day column study revealed that the GO/HDTMA sponge is a good filtering material for the removal of Cu(II) from river water. In conclusion, the GO/HDTMA sponge is an excellent adsorbent material for use in flow-through water treatment applications for Cu(II) removal.

Sustainable carboxylated cellulose filters for efficient removal and recovery of lanthanum

Carboxylated cellulose filters were fabricated by oxidation of a cellulose fibrous mat via TEMPO-mediated oxidation. These carboxylated cellulose filters were employed as sustainable filters for removal and recovery of lanthanum ions (La (III)) with high adsorption capability. The surface chemistry of the carboxylated cellulose fibers before and after adsorption of La (III) was investigated systematically. The distribution of La (III) on carboxylated cellulose fibers were explored by EDX mapping approach, which revealed that the adsorption occurred on both the surface and the internal structure of the cellulose fibers. The kinetics and isotherms of the adsorption were conducted to understand the adsorption mechanism of the carboxylated cellulose filter and to learn the maximum adsorption capacity for La (III) which was as high as 33.7 mg/g. The adsorption selectivity of the carboxylated cellulose filter for La (III) was determined when interfering ions including mono- and di-covalent ions were involved. The carboxylated cellulose filter exhibited high adsorption capability and high permeation flux evidenced by the breakthrough curves of the dynamic adsorption of La (III) under an extremely low pressure of 0.07 kPa. A variety of desorption reagents were selected to recover lanthanum from the carboxylated cellulose filter, where the optimized conditions for recovery were explored. Finally, a spiral wound cartridge of the carboxylated cellulose fibrous mat was fabricated and the removal and the recovery of La (III, 2.5 ppm) from massive lanthanum-containing water were demonstrated. It was very impressive that the high rejection ratio of 94.3% was achieved under the low pressure drop of 3.0 kPa remaining throughout the separation process, and the treated solution volume was high up to 21.4 L, which was about six-times higher than that of commercially available nanofibrous adsorption membranes, indicating that the carboxylated cellulose filter could be used as a highly efficient adsorption medium for industrial recovery of rare earth metals.

Modification of Silica Nanoparticles with Cysteine or Methionine Amino Acids for the Removal of Uranium (VI) from Aqueous Solution

Silica nanoparticles (SiO2-NPs), modified silica nanoparticles with cysteine (SiO2-Cys) or methionine (SiO2-Meth) were used for sorption of uranium (VI) ion from aqueous solution. Silica nanoparticles and its modified forms were prepared and characterized by elemental analysis, FTIR, XRD, XRF, TGA, DSC, SEM, TEM, BET and zeta potential. Sorption of uranium(VI) ion using batch technique by silica nanoparticles, SiO2-Cys and SiO2-Meth was studied as a function of initial concentration, sorbent dosage, pH, contact time and temperature. The percent uptakes for silica nanoparticles, SiO2-Cys, SiO2-Meth were 27%, 33%, 30% respectively for U(VI) ion at 25 °C. The kinetic studies show that sorption of U(VI) ion by silica nanoparticles, SiO2-Cys and SiO2-Meth was well described by the pseudo second order equation. Negative values of Gibbs free energy (ΔG°) suggest the spontaneity of the sorption process on silica nanoparticles and its modified forms (SiO2-Cys) and (SiO2-Meth). Positive values of enthalpy (ΔH°) indicate endothermic adsorption process. The sorption isotherm was better fitted by Langmuir model with maximum sorption capacity for silica nanoparticles, SiO2-Cys and SiO2-Meth was found to be 3.6, 4.5, 3.8 mg/g respectively. Desorption studies indicate that the most favorable desorption reagent for uranium(VI) is 0.1 M HNO3 and the highest percent recovery was achieved from silica nanoparticles (~71%) than its modified forms SiO2-Cys and SiO2-Meth.

Visualization analysis of graphene and its composites for heavy metal wastewater applications.

In order to explore the research trends and hotspots related to the treatment of heavy metals in wastewater by graphene and its composites, this study collected information on 511 publications from the Science Citation Index-Expanded (SCIE) and conducted a quantitative and visual analysis. The article on the adsorption of heavy metals in wastewater by graphene and its composites first appeared in 2006 and continued to grow since 2011. It broke through 100 articles for the first time in 2016 and the overall trend is on the rise. The 511 articles were published in 185 journals, of which RSC Advances is the most dynamic journal, and Journal of Materials Chemistry A is the most authoritative journal. Asian authors published about 87.14% of papers, and China, Iran, and India played a leading role compared with other countries. The University of Chinese Academy of Sciences is the largest research institution for the adsorption of heavy metals in wastewater by graphene and its composites. Hot keywords are "heavy metal removal," "water sample," "recent advance," "reusable adsorbent," "graphene-based material," and "composite nanosheet." Combined with keywords and cluster analysis, the chemical modification of graphene oxide has become a hot research direction for graphene materials to remove heavy metals from wastewater. Among them, MnFe2O4-graphene composite is a hot spot for graphene modification. In general, HNO3, HCl, and EDTA are desorption reagents for graphene and its composites.

Desorption of calcium-rich crayfish shell biochar for the removal of lead from aqueous solutions

In this study, crayfish shell was pyrolyzed at 600 °C to obtain a calcium-rich biochar (CS600). The biochar was saturated with Pb2+ in batch adsorption experiment. Six desorption reagents including HCl, HNO3, H2SO4, NaOH, EDTA and EDTA-2NaCa were then used to desorb Pb2+ from the post-adsorption CS600 to determine the desorption mechanism. Lead adsorption experiments were performed to determine the adsorption capacity of the regenerated CS600. HCl, HNO3, EDTA and EDTA-2NaCa presented good desorption effect with desorption rates all over 80%. Most of the regenerated biochars lost their lead adsorption ability due to the destruction of CaCO3 mineral on their surface. Only the one desorbed by EDTA-2NaCa retained a preferable lead adsorption capacity. EDTA-2NaCa thus is a promising desorption reagent of CS600 for the removal of lead from aqueous solutions.

Removal and recovery of lead from wastewater using an integrated system of adsorption and crystallization

This study explores the feasibility of an integrated system comprising adsorption and crystallization in a pellet reactor to remove and recover lead from aquatic environment. The selective adsorption of Pb2+ over Ca2+ and Mg2+ was investigated using citric acid modified sugarcane bagasse (SCA) in batch and column systems. Selective separation of Pb2+ from the mixed solution was achieved at a molar ratio 3.22 <Co,batchCa+Mg/Co,batchPb < 4.49 in batch mode while in a packed bed column, lead was selectively adsorbed by SCA up to a capacity of 0.767 mmol/g with a bed height of 7 cm, a flow rate of 1.5 ml/min and an initial lead concentration of 0.482 mmol/L. The dynamic study shows a close agreement between the experimental results and the Thomas and Yoon-Nelson models. The desorption study of equilibrium biosorbent SCA in a column system demonstrates that sodium chloride is a promising desorption reagent, with a desorption capacity of 80% Pb2+. In addition, synthetic lead wastewater with characteristics simulating the concentrate from desorption of saturated SCA was further treated in a fluidized bed denoted as pellet reactor. Lead (II) was quantitatively recovered at optimized conditions of pH 10, molar ratio [CO32−]: [Pb2+] = 3:1, superficial velocity 9.55 m/h, and initial lead concentration 2.43 mM. The well-controlled crystallization process of cerussite on the surface of grain sand in the pellet reactor is comparable with the chemical equilibrium speciation data obtained by Visual MINTEQ. Overall, the developed system comprising adsorption combined with a pellet reactor was found sufficient to remove and recover lead as PbCO3 from wastewater.

Selective Extraction and Antioxidant Properties of Thiol-Containing Peptides in Soy Glycinine Hydrolysates.

A highly selective procedure to extract thiol-containing peptides (TCPs) from complicated soy glycinin hydrolysates (SGHs) was described. This procedure included the reduction of disulfide bonds by 1,4-dithiothreitol (DTT) and enrichment of TCPs through Thiopropyl-Sephrose 6B covalent chromatography. TCPs were confirmed using a strategy based on mass shift after differential alkylation of sulfhydryl groups with iodoacetamide and N-ethylmaleimide by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS). The antioxidant activities of TCPs were evaluated using chemical assays. DTT reduction increased the concentration of sulfhydryl groups from 1.8 μmol/g to 113.8 μmol/g. The efficiency of the extraction was improved by optimizing the loading of sample, extraction and desorption time and the content of desorption reagent. Both of the adsorption and desorption process were found to fit a pseudo-second order model. MALDI-TOF-MS showed that 36 of the 45 extracted peptides were TCPs. The EC50 of TCPs for DPPH, hydroxyl radical, and superoxide anion radical was 0.1, 1.49 and 0.084 mg/mL, respectively. The reducing power of TCPs (0.2 mg/mL) was of 0.375. These results suggest that the combination of DTT reduction and Thiopropyl-Sepharose 6B covalent chromatograph was a successful pathway to extract TCPs from SGHs and the TCPs could be used as potential antioxidants.

Study on the Preparation of Mercaptoacetic Acid-modified Heterophylla Shell and Its Application in Separation and Enrichment of Pb2+ in Environmental Samples

To increase the adsorption capacity of the Corylus heterophylla Fisch(HS) for Pb2+, HS was chemically modified using NaOH aqueous solution and 95% ethanol and was labeled as SHS; then SHS was chemically modified using mercaptoacetic acid. The SHS modified with mercaptoacetic acid(MHS) was characterized using FTIR, SEM, and XPS. The results indicated that the —SH group was present on MHS, and after Pb2+ adsorption, the absorption value of the characteristic peak of the —SH group decreased. The adsorption and desorption properties of this functionalized material were investigated as well as the influences of parameters, such as pH value, type of desorption reagent, dosage, flow rate and maximum sample volume. The Pb2+ adsorption of MHS reached a maximum with pH>5. The experimental data of Pb2+ adsorption using MHS were fitted using the Langmuir isothermal adsorption model, and a maximum adsorption capacity of 61.54 mg/g was obtained. This was much higher than the adsorption capacity of SHS before modification with the thiol group. After adsorption, MHS was desorbed using a 0.2 mol/L HCl solution, and the percent of desorption was higher than 99%. MHS was used as a solid-phase extractant in the analysis and determination of Pb2+ content in food and water samples, and the enrichment times achieved 150-fold.

Poly(1-vinylimidazole) functionalized magnetic ion imprinted polymer for fast and selective extraction of trace gold in geological, environmental and biological samples followed by graphite furnace atomic absorption spectrometry detection

In this study, poly(1-vinylimidazole) functionalized gold ion imprinted polymer coated magnetic nanoparticles (MNPs@PVIM-Au-IIP) were prepared and characterized. The adsorption behaviors of the prepared MNPs@PVIM-Au-IIP toward gold ions (Au(III)) were studied, it was found that MNPs@PVIM-Au-IIP has good selectivity, high adsorption capacity (185.4mgg−1) and fast adsorption kinetic for Au(III). Based on it, a new method of ion imprinted magnetic solid phase extraction (II-MSPE) coupled with graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the analysis of trace Au(III) in real samples with complicated matrix. Factors affecting MSPE including sample pH, desorption reagent, elution concentration and volume, elution time, sample volume and adsorption time were optimized. With high enrichment factor of 100-fold, the detection limit of the proposed method is 7.9ngL−1 for Au(III) with the relative standard deviation of 7.4% (c=50ngL−1, n=7). In order to validate the accuracy of the proposed method, the Certified Reference Material of GBW07293 geological sample (platinpalladium ore) was analyzed, and the determined value was in good agreement with the certified value. The proposed II-MSPE-GFAAS method is simple, fast, selective, sensitive and has been successfully applied in the determination of trace Au in ore, sediment, environmental water and human urine samples with satisfactory results.

Graphene oxide/chitosan sponge as a novel filtering material for the removal of dye from water

Although graphene oxide (GO)-based materials are attractive media for water treatment, their separation from water for reuse remains a challenge. This study investigated the self-assembly of GO sheets in the presence of chitosan (CS), a natural polyaminosaccharide, into sponges. We found that about 93% of added CS could be combined with GO, regardless of the CS concentration. There exists an upper critical gelation limit, below which hydrogel forms and above which precipitation takes place. Results indicate that upon freeze-drying, a stable GO/CS sponge was generated only at a CS content of ≥9%. Sponges with CS content between 9% and 41% had good filtering performance. The sponges were characterized with XRD, SEM and FTIR measurements and the interaction between GO and CS was analyzed. The GO/CS sponge with CS content of 9% had adsorption capacity of 275.5 mg/g for methylene blue (MB), a model dye molecule. Both electrostatic attraction and hydrophobic interactions are responsible for MB adsorption by GO/CS sponges. The GO/CS sponge could be regenerated for repeated use using 0.5 M NaOH solution as desorption reagent. Our fixed-bed column studies illustrate that the GO/CS sponge performed well as a filtering material for removing MB from water.

Palladium(II) sorption of a diethylphosphate-modified thiacalix[6]arene immobilized on amberlite resin

p-Diethylphosphonomethylthiacalix[6]arene (1) was impregnated on Amberlite XAD-7 resin (1-XAD), and the sorption kinetics of 1-XAD towards Pd(II) ions in HCl media were investigated. The maximum Pd(II) sorption capacity (SC) of 1-XAD was 18.7mgg−1 after a contact time of 24h in a 200mgL−1 Pd(II) solution. Batch sorption studies were then conducted to optimize a range of equilibration conditions, such as contact time, Pd(II) concentration, and temperature. The sorption process was then explained in the context of Freundlich and Langmuir isotherm models, thermodynamic parameters ∆G°, ∆H°, and ∆S°, and sorption kinetics were calculated to understand the nature of the sorption. Pd(II) sorption with 1-XAD was found to be spontaneous and endothermic nature. Pd(II) sorption kinetics follows a pseudo-second-order model. In addition, the SC of 1-XAD was investigated using the leach liquors of automotive catalysts containing Al, Ba, Ce, La, Pd, Pt, and Rh ions. The resin developed herein exhibited high selectivity towards Pd(II) ions, with a SC value of 4.12mgg−1 being obtained from leach liquors of automotive catalysts. Finally, Pd(II) desorption from Pd(II)-sorbed 1-XAD was achieved using a thiourea solution as the desorption reagent, and the resin was reused effectively over 5cycles. Pd(II) separation using the 1-XAD as a adsorbent is eco-friendly method as compared with conventional solvent extraction. The 1-XAD is highly useful for selective recovery of Pd(II) from leach liquors of automotive catalysts and secondary resources.