Qm Value Research Articles

Study the Use of Activated Carbon and Bone Char on the Performance of Gravity Sand-Bag Water Filter.

In this study, granulated activated charcoal (GAC) and bio charcoal (BC) is used as a filler in P3 biosand bag filter to study their filtration performance against a range of fluoride impurities from 1–1400 mg/L. A set of experiments are done to analyze the filtration efficiency of the sandbag filter against fluoride impurities after incorporating different amounts (e.g., 0.2, 2 kg) and a combination of GAC and BC. A combination of filler GAC and BC (1 kg each) have exhibited excellent results with 100% fluoride removal efficiency against 5 mg/L fluoride impurities for an entire experimental time of 165 min. It is because of the synergetic effect of adsorption caused by the high surface area (739 m2/g) of GAC and hydroxyapatite groups in BC. The data from remediation experiments using individual GAC and BC are fitted into the Langmuir and Freundlich Isotherm Models to check their adsorption mechanism and determine GAC and BC’s maximum adsorption capacity (Qm). The remediation data for both GAC and BC have shown the better fitting to the Langmuir Isotherm Model with a high R2 value of 0.994 and 0.970, respectively, showing the excellent conformity with monolayer adsorption. While the GAC and BC have presented negative Kf values of −1.08 and −0.72, respectively, for Freundlich Model, showing the non-conformity to multilayer adsorption. The Qm values obtained from Langmuir Model for GAC is 6.23 mg/g, and for BC, it is 9.13 mg/g. The pH study on adsorption efficiency of individual GAC and BC against 5 mg/L of fluoride impurities indicates the decrease in removal efficiency with an increase in pH from 3 to 9. For example, BC has shown removal efficiency of 99.8% at pH 3 and 99.5% at pH 9, while GAC has exhibited removal efficiency of 96.1% at pH 3 and 95.9% at pH 9. Importantly, this study presents the significance of the synergetic application of GAC and BC in the filters, where GAC and BC are different in their origin, functionalities, and surface characteristics.

Treatment of real industrial wastewater with high sulfate concentrations using modified Jordanian kaolin sorbent: batch and modelling studies

In the present study, BaCl2 modified Jordanian kaolin sorbent (obtained from Mahis, Jordan) was used to remove sulfate-contaminated industrial wastewater. The kaolin sample was pretreated to enhance its adsorption capacity and then characterized using X-Ray fluorescence (XRF) and Fourier Transform Infrared Spectroscopy (FTIR). Equilibrium isotherms for the adsorption parameters were carried out experimentally, and the adsorption data correlated very well with Freundlich and Temkin and Dubinin-Radushkevich models. Furthermore, the adsorption kinetics followed the pseudo-first-order and intraparticle diffusion models perfectly. The estimated value of the maximum adsorption capacity qm = 85.08 mg/g indicates that kaolin has a very high capacity to adsorb sulfate ions at studied parameters. The estimated value of the mean free energy (4.87 kJ/mol) is very low, confirming physical type adsorption. The study results established that modified Jordanian kaolin could serve as a safe and effective natural adsorbent for sulfate-contaminated industrial wastewater.

Adsorption of antiretroviral drugs, efavirenz and nevirapine from aqueous solution by graphene wool: Kinetic, equilibrium, thermodynamic and computational studies

The increasing concentrations of pharmaceutical and personal care products in water bodies have attracted attention due to the risk of non-target exposures. The application of any graphene-based material for the remediation of antiretroviral drug contamination has not been reported, therefore graphene wool was synthesized by chemical vapour deposition as adsorbent for the removal of efavirenz (EFV) and nevirapine (NVP) from water. Results revealed that adsorption of EFV was best fitted to the intraparticle diffusion model, with multi-linearity (multiple adsorption steps). The pseudo-second-order model best describes GW-NVP interaction. Isotherm parameters revealed that Sips and Freundlich model best fit GW-EFV and GW-NVP interactions, with the least value of SSE < 0.04 and 1.27, respectively. GW demonstrated higher adsorption capacity and adsorption maxima for NVP with Kd and qm values of ∼ 2.54 L/g and ∼ 48.31 mg/g, compared to ∼ 1.48 L/g and ∼ 4.41 mg/g obtained for EFV adsorption. Isotherm parameters suggest that GW adsorbed NVP slightly better with stronger binding strength than EFV, with removal efficiencies of 84% (NVP) and 80% (EFV) under optimum conditions. A heterogeneous adsorption mechanism was suggested for GW-EFV sorption, in contrast to a less heterogeneous and multilayer adsorption mechanism for GW-NVP adsorption. NVP adsorption is a spontaneous exothermic process, while GW-EFV interaction is a spontaneous endothermic process. Experimental results were supported by computational studies, which revealed the influence of strong dispersion interactions and H-bonding at specific pH ranges.

Research on the control law of dust in the main ventilation system in excavated tunnels for cleaner production

This study was based on computational fluid dynamics (CFD) and field measurement verification. First, we researched and analyzed the main ventilation system, when closed or opened, of a tunnel boring machine (TBM), to demonstrate that the main ventilation system had the ability to control dust. Then, summarized the theory of pressure airflow dust control in an excavated tunnel. Next, the airflow volume (QM) of the main ventilation system was modified based on different excavation lengths and by adjusting the values of QM from 5 m3/s to 40 m3/s. We found that when QM = 25–30 m3/s, the dust could be effectively controlled, the dust in the working area was effectively controlled within 45.5–55.6 m, and the dust concentration was reduced to less than 9.59–10.50 mg/m3. The accuracy of the CFD results was verified through field measurement, which also showed that the dust concentration was effectively reduced. In conclusion, that the main ventilation system functioned to both supply oxygen and control dust, helping to protect the health of tunnel workers.

Production of innovative magnetic adsorbent Fe3O4@PEI®Tween 85 and removal of oxytetracycline from aqueous media

ABSTRACT The presence of pharmaceutical in waters has raised the challenge of antimicrobial resistance. This paper presents a study on the adsorption of Oxytetracycline (OTC) from an aqueous using a modified Iron Oxide (Fe3O4) which was modified with Polyethyleneimine (PEI) polymer and coated with Polyoxyethylene Sorbitan Trioleate (Tween 85) surfactant. The adsorption performance was examined the effect of pH, temperature, contact time, adsorbent dosage and drug concentration based on batch experiments. High OTC removal rates of about 98% for the 1:2 with Tween 85 were obtained at pH 4, similar removal efficiency was obtained for the 1:2 Tween 85-free at pH 3. Also, it was seen that the adsorption process was a physical and exothermic process in terms of thermodynamics. The adsorption can be well explained by Freundlich isotherm model. The results demonstrate that the modified magnetic material, with low concentration of 0.025 g, have great potential to capture OTC. Also, qm value (277.8 mg/g) of the adsorbent shows its great potential and the adsorbent reaches its maximum capacity in a short time (~10 minutes).The experimental results reveal that Fe3O4@PEI®Tween 85 would be a promising solution with high removal efficiency and low-cost adsorbent for water matrices protection.

A MEMS Fabrication Process with Thermal-Oxide Releasing Barriers and Polysilicon Sacrificial Layers for AlN Lamb-Wave Resonators to Achieve fs·Qm > 3.42 × 1012.

This paper presents a micro-electro-mechanical systems (MEMS) processing technology for Aluminum Nitride (AlN) Lamb-wave resonators (LWRs). Two LWRs with different frequencies of 402.1 MHz and 2.097 GHz by varying the top interdigitated (IDT) periods were designed and fabricated. To avoid the shortcomings of the uncontrollable etching of inactive areas during the releasing process and to improve the fabrication yield, a thermal oxide layer was employed below the platted polysilicon sacrificial layer, which could define the miniaturized release cavities well. In addition, the bottom Mo electrode that was manufactured had a gentle inclination angle, which could contribute to the growth of the high-quality AlN piezoelectric layer above the Mo layer and effectively prevent the device from breaking. The measured results show that the IDT-floating resonators with 12 μm and 2 μm electrode periods exhibit a motional quality factor (Qm) as high as 4382 and 1633. The series resonant frequency (fs)·Qm values can reach as high as 1.76 × 1012 and 3.42 × 1012, respectively. Furthermore, Al is more suitable as the top IDT material of the AlN LWRs than Au, and can contribute to achieving an excellent electrical performances due to the smaller density, smaller thermo-elastic damping (TED), and larger acoustic impedance difference between Al and AlN.

Engineered hard piezoelectric materials of MnO2 doped PZT-PSN ceramics for sensors applications

ABSTRACT In this study, MnO2-doped 0.96Pb(Zr0.515,Ti0.485)O3-0.04Pb(Sb0.5,Nb0.5)O3 (0.96PZT-0.04PSN) hard piezoelectric ceramics were fabricated by employing a conventional mixed-oxide process. Hard piezoelectric materials are suitable for mechanical device applications such as transducers or piezoelectric ultrasonic motors owing to their high mechanical quality factor. To improve the hard piezoelectric properties, MnO2 was selected and doped into 0.96PZT-0.04PSN ceramics in this study. When MnO2 was introduced into piezoelectric lead zirconate titanate (PZT) ceramics, the resistivity and dielectric permittivity decreased, leading to an increase in the mechanical quality factor. MnO2-doped 0.96PZT-0.04PSN ceramics have a lower piezoelectric charge coefficient and dielectric permittivity compared to those of 0.96PZT-0.04PSN ceramics. However, an enhanced mechanical quality factor of 1600 was obtained for the 0.96PZT-0.04PSN ceramics doped with 0.5 wt% of MnO2. In contrast to other hard piezoelectric materials, MnO2 doped 0.96Pb(Zr0.515,Ti0.485)O3-0.04Pb(Sb0.5,Nb0.5)O3 ceramics have a high Qm value while having an appropriate piezoelectric charge coefficient d33 and electromechanical coupling coefficient kp.

Electromechanical properties of barium titanate-polyvinylidene fluoride cement-based composites

In this study, 40–60 vol% barium titanate (BT) piezoelectric ceramic particles, Portland cement, and polyvinylidene fluoride (PVDF, 0–7 vol%) were used to fabricate 0–3 BT cement-based composites. The electromechanical coupling factor (k) and the mechanical quality factor (Qm) of the composites were investigated. Increasing BT and PVDF contents led to a decreased impedance of the composite. Moreover, the impedance peak detected was found to shift to a lower frequency. Broaden impedance peak can be observed when PVDF content increased. The electromechanical coupling factor of thickness mode (kt) and planar mode (kp) increased with increasing BT and PVDF contents. The highest values for kt (16.74%) and kp (16.94%) were found in the composite with 60 vol% BT and 5–7 vol% PVDF. The composite with no PVDF has a higher Qm value than composites with PVDF. The lowest Qm value can be observed at 3 vol% PVDF with all BT content.

Surface improved agro-based material for the effective separation of toxic Ni(II) ions from aquatic environment

In this present study, a novel and low cost surface improved material was prepared from the farm waste material (Borassus flabellifer male inflorescence) and its surface was enhanced by the sulphuric acid treatment to intensify the Ni(II) ions adsorption. The adsorption individualities such as availability of functional groups, essential elements and the exterior side and structural properties of the material were assessed by the FT-IR, EDX, SEM and XRD investigation. The impact of varied adsorption influencing parameters on Ni(II) ions adsorption was studied and optimized as pH - 6.0, biosorbent dosage - 1.5 g/L, contact time - 60 min and temperature - 303 K via batch adsorption examination. Modeling examinations were carried with varied adsorption isotherm (Langmuir, Freundlich, Fritz-Schlunder and Temkin) and kinetic models (Pseudo-first order, Pseudo-second order and Elovich kinetics). Thermodynamic studies were carried out at varied Ni(II) ions concentrations (25 mg/L – 150 mg/L) and temperatures (303 K–333 K) to explain the nature of Ni(II) ions adsorption on Borassus flabellifer male inflorescence. The prepared material has shown the most suitable Ni(II) ions adsorption results for the Langmuir isotherm (R2 = 0.9808) and Pseudo-first order kinetic models (R2 = 0.9735 for 25 mg/L). Thereby, the modeling study revealed that the prepared material has received the Ni(II) ions adsorption capacity (qm) value of 20.31 mg/g and the Ni(II) ions adsorption was physisorption. Thermodynamic results demonstrated that the Ni(II) ions adsorption was immediate, exothermic and favorable at low temperature.

Deferoxamine-Modified Hybrid Materials for Direct Chelation of Fe(III) Ions from Aqueous Solutions and Indication of the Competitiveness of In Vitro Complexing toward a Biological System.

Deferoxamine (DFO) is one of the most potent iron ion complexing agent belonging to a class of trihydroxamic acids. The extremely high stability constant of the DFO–Fe complex (log β = 30.6) prompts the use of deferoxamine as a targeted receptor for scavenging Fe(III) ions. The following study aimed at deferoxamine immobilization on three different supports: poly(methyl vinyl ether-alt-maleic anhydride), silica particles, and magnetite nanoparticles, leading to a class of hybrid materials exhibiting effectiveness in ferric ion adsorption. The formed deferoxamine-loaded hybrid materials were characterized with several analytical techniques. Their adsorptive properties toward Fe(III) ions in aqueous samples, including pH-dependence, isothermal, kinetic, and thermodynamic experiments, were investigated. The materials were described with high values of maximal adsorption capacity qm, which varied between 87.41 and 140.65 mg g–1, indicating the high adsorptive potential of the DFO-functionalized materials. The adsorption processes were also described as intense, endothermic, and spontaneous. Moreover, an exemplary magnetically active deferoxamine-modified material has been proven for competitive in vitro binding of ferric ions from the biological complex protoporphyrin IX–Fe(III), which may lead to a further examination of the materials’ biological or medical applicability.

Effect of Montmorillonite Layer Charge on the Thermal Stability of Bentonite

AbstractThe thermal stability of bentonite is vitally important for its application in the casting field and the layer charge of montmorillonite (Qm) is one of its central crystal-chemical parameters. As the main component of bentonite, the influence of Qm on montmorillonite properties and behavior needs to be considered if bentonite is to be used in high-temperature environments. The objective of the current study was to investigate the relationship between Qm and the thermal stability of Chinese bentonite samples collected from Wuhu, Anhui Province (marked as WH); Xinyang, Henan Province (marked as XY); and Santai, Sichuan Province (marked as ST) below. The values of Qm were obtained using the O (11) method, and the structural properties of the bentonite samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry-differential scanning calorimetry (TG-DSC), and field emission scanning electron microscopy (FESEM). The results showed that, in the samples investigated, Qm was inversely related to the thermal stability of bentonite. The Qm value (electrons per half unit cell, e/huc) was greatest for sample ST (0.725 e/huc), followed by sample XY (0.470 e/huc), and by sample WH (0.354 e/huc). The dehydroxylation temperature changed related to Qm; the sample with the largest Qm value was WH (701°C), followed by sample XY (684°C), and sample ST (630°C). After the samples were calcined at 600°C, sample WH had the best montmorillonite structural integrity with the greatest degree of reusability (78.21%); while the montmorillonite structures of samples XY and ST were destroyed, and their reusabilities were only 9.48 and 6.01%, respectively.

Iron Oxide (Fe3O4)-Supported SiO2 Magnetic Nanocomposites for Efficient Adsorption of Fluoride from Drinking Water: Synthesis, Characterization, and Adsorption Isotherm Analysis

This research work reports the magnetic adsorption of fluoride from drinking water through silica-coated Fe3O4 nanoparticles. Chemical precipitation and wet impregnation methods were employed to synthesize the magnetic nanomaterials. Moreover, the synthesized nanomaterials were characterized for physicochemical properties through scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray powder diffraction. Screening studies were conducted to select the best iron oxide loading (0.0–1.5 wt%) and calcination temperature (300–500 °C). The best selected nanomaterial (0.5Fe-Si-500) showed a homogenous FeO distribution with a 23.79 nm crystallite size. Moreover, the optimized reaction parameters were: 10 min of contact time, 0.03 g L−1 adsorbent dose, and 10 mg L−1 fluoride (F−) concentration. Adsorption data were fitted to the Langmuir and Freundlich isotherm models. The Qm and KF (the maximum adsorption capacities) values were 5.5991 mg g−1 and 1.869 L g−1 respectively. Furthermore, accelerated adsorption with shorter contact times and high adsorption capacity at working pH was among the outcomes of this research work.

Biosorption of Copper (II) Ion from Aqueous Solution Using Algae Biomass Oscillatoria sp

Biosorption is the method of removing heavy metal from the aqueous solution. Oscillatoria sp microalgae were used to adsorb copper ions in this study. The maximum biosorption capacity was obtained 4.9 mg/g at pH of 9 with an efficiency of 99%. The algae dosage in 0.1 g gave the maximum capacity of 12.33 mg/g. The maximum contact time occurred at 60 minutes with an adsorption capacity of 19.87 mg/g. Adsorption Cu2+ by microalgae Oscillatoria sp followed by the Langmuir and Freundlich isotherms. According to the Langmuir models the value of qm is 217.39 mg/g , KL = 8.8 x10-4 L/mg, and R2 = 0.9999. The Freundlich model showed the coefficient correlation R2 = 1, 1/n = 1.0162, and Kf = 5.39. The model of pseudo-second-order with qe = 4.98 mg/g, k2 = 81.38 g mg-1 h-1, and R2 = 1.

Comparison of Heavy Metals Removal from Aqueous Solution by Moringa oleifera Leaves and Seeds

In this work, biomass obtained from seeds (S-MO) and leaves (L-MO) of the Moringa oleifera plant were used as low-cost biosorbents to remove the Pb(II), Cd(II), Co(II), and Ni(II) from aqueous solutions. The biosorption of the heavy metal ions was done using the batch technique. The effects of contact time (30–1440 min), biosorbent dosage (10–50 g/L) (0.1–0.5 g), and initial concentration of metals (10–500 mg/L) on the sorption capacity of metal ions were investigated. The S-MO and L-MO samples’ characterization was performed using pHpzc, X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). It was found that the pHpzc was notably different between the seeds and leave-derived biosorbents. The removal process’s experimental kinetic data for both S-MO and L-MO were best described by the pseudo-second-order model for all metal ions, with R2 above 0.997 in all cases. Langmuir and Freundlich’s models were also used to analyze the isotherms parameters. Based on the Langmuir model, the maximum sorption capacities (Qm) for L-MO were found as follows: L-MO-Pb &gt; L-MO-Cd &gt; L-MO-Co ≥ L-MO-Ni, and for S-MO, the values of Qm values presented the following order: S-MO-Pb &gt; S-MO-Co &gt; S-MO-Cd &gt; S-MO-Ni.

Application of modified green algae Nannochloropsis sp. as adsorbent in the simultaneous adsorption of Methylene Blue and Cu(II) cations in solution

Biomass of algae is a very potent adsorbent for absorbing aqueous waste containing heavy metals and organic dyes. This study purposes to confirm the ability of adsorbents from green algae Nannochloropsis sp. modified with silica (ASN) and followed by coating magnetite particles (ASN-MPs) to absorb simultaneously the mixture of Methylene Blue (ME) and Cu(II) cations in aqueous solution. Simultaneous sorption of ME and Cu(II) cations to ASN and ASN-MPs was carried out by the batch method with the interaction pH condition 7, contact time 90 min, and initial concentrations of ME and Cu(II) cations (0.1–1.0 mM). Based on adsorption data, Cu(II) cations have a greater adsorption rate and capacity (qm) compared to ME at the same contact time and initial concentration. The adsorption capacity (qm) values of the bi-component ME and Cu(II) cation mixture in ASN and ASN-MPs were 1.39 × 10− 1 and 5.32 × 10− 1 mmol g− 1, respectively, with the binary Langmuir adsorption isotherm constant for Cu(II) cations greater than ME. Modified adsorbent from algae Nannochloropsis sp. with silica matrix and magnetite particle coating is an adsorbent that has a high effectiveness in the collective sorption of ME and Cu(II) cations. Therefore, these adsorbents can be used for the adsorption of cation mixtures of heavy metals and organic dyes that are cationic in solution.

3D porous bioadsorbents based on chitosan/alginate/cellulose nanofibers as efficient and recyclable adsorbents of anionic dye

Natural polysaccharides are attractive materials for fabrication of eco-friendly biodsorbents for efficient water remediation. However, scarcity of adsorbents that possess features of high stability and adsorption capacity at various pH conditions, low-cost, eco-friendly, and recycleability at the same time still remains a great challenge. Herein, porous ionically crosslinked biofoams were prepared by freeze-drying of chitosan (CS)/sodium alginate (SA) complex (CSA). FTIR and XRD were used to characterize the structure of the bioadsorbents. SEM observations revealed that adsorbents have a 3D interconnected porous structure, which is a favorable morphology for dye adsorption. Accordingly, CSA and its nanocomposite containing 15 wt% cellulose nanofibers (CSAC15) exhibited a fast and efficient adsorption behavior with qm values of 2015 and 2297 mg/g for adsorption of the Eriochrome black-T (EBT) anionic dye, respectively, which are quite outstanding among the developed EBT adsorbents in the literature so far. The CSAC15 preserved its stability and high adsorption capacity at various pH solutions. The adsorption of EBT onto the bioadsorbents was well-described with the pseudo-second order kinetics and Freundlich isotherm. The proposed CSAC15 bioadsorbent featured repeated dye removal capability after five cycles of adsorption.

Investigation of methylene blue adsorption from aqueous solution onto ZnO nanoparticles: equilibrium and Box-Behnken optimisation design

ABSTRACT Throughout this report, ZnO nanoparticles are synthesised by co-precipitation as a new adsorbent. XRD, FTIR, SEM, PL, and UV-visible spectroscopy characterise the obtained nanoparticles. Characterisation of prepared nanoparticles provided evidence of the impact of duration of calcination on particle size and morphology. The new adsorbent was used to remove cationic dye (methylene blue (MB)) from aqueous solutions by batch adsorption technique. The effect of pH, adsorbent dosage, ion strength, contact time, and the temperature was investigated. The pHPZC was approximately pH 7.2. The results revealed that an amount of 0.1 g/L ZnO-NPs showed maximum removal efficiency of each dye (50 ppm) at pH 8.5. The adsorption process of the MB followed the Langmuir model with a correlating constant (R2) higher than 0.99 and with a maximum capacity (qm) value of 62.5 mg/g. The pseudo-second-order (R2 > 0.9986) model was most appropriate in the description of the adsorption process. Thermodynamic parameters ΔS0(0.0001 J/mol K), ΔH0 (– 3,692 kJ/mol), and ΔG0(between − 4.143 to and – 4.189 kJ/mol) were investigated at four temperatures (25, 35, 45, and 55°C). The uptake process of the MB occurs spontaneously following an exothermic process and shows that the adsorption follows the physisorption mechanism. It would appear that hydrogen bonding was included in the potential mechanism governing MB adsorption on the ZnO nanoparticles at pH 8.5. In order to optimise various process parameters, e.g. pH solution (X1: 4–11), adsorbing dose (X2: 0,01–0,1 g/L), [MB] Concentration dye (X3: 50–300 mg/L), and contact time (X4: 20–120 min), Box–Behnken, design (BBD) in response surface methodology (RSM) was used. The experimental results were based on a second-order polynomial equation. Overall, the adjusted coefficient of determination (R2) value of 0.99 indicated that the used model was quite suitable and the selected RSM was successful in optimising the decolarizations conditions of MB.

On a contextual model refuting Bell's theorem

Bell's theorem is refuted by presenting a counterexample that correctly predicts the expectation values of QM. As Bell only ruled out non-contextual models, a contextual model with hidden variables can refute his theorem. Such a model, which is able to explain the spin measurement results with entangled photons or electrons, is presented herein. It is not ruled out by the Kochen-Specker theorem. A physical justification for the contextual behaviour of entangled systems is provided. Consequences for the feasibility of quantum computers are discussed.

Rapid and selective magnetic separation of uranium in seawater and groundwater using novel phosphoramidate functionalized citrate-Fe3O4@Ag nanoparticles

One-pot magnetic separation of uranium (U) in seawater and groundwater samples has been made possible by synthesizing phosphoramidate functionalized Ag coated citrate-Fe3O4 nanoparticles (NPs). The magnetic saturation value of these functionalized NPs is 27.1 emu g−1. The synergistic extraction mechanism of U(VI) ion by the surface-modified phosphoramidate and citrate molecules make these NPs highly selective towards U(VI). The adsorption kinetics follows a pseudo-second-order model and the adsorption isotherm fits successfully to the Langmuir adsorption model. The functionalized NPs show quantitative extraction efficiency in the pH range of 6.5–8 with a maximum loading capacity (Qm) of 108.7 mg g−1. The equilibration time required by these functionalized NPs to attain the Qm value is 120 s. The recycling of these NPs can be done up to 5–6 times with 1.0 mol L−1 of Na2CO3 or NH4OH for quantitative extraction of U(VI). These functionalized NPs show high resilience towards large number of naturally abundant metal ions.

Comparative research on selective adsorption of Pb(II) by biosorbents prepared by two kinds of modifying waste biomass: Highly-efficient performance, application and mechanism

In this study, we used xanthate to modify two waste biomass materials (corn cob and chestnut shell) and prepared them as biosorbents in one step for effectively removing Pb(II) from aqueous solutions containing only Pb(II) or Pb(II), Cu(II) and Cd(II). The two biosorbents were characterized by SEM, EDS, FTIR and Zeta potential analysis, and the results of the characterization were used to explore the adsorption mechanism of Pb(II) on biosorbents. We compare the Pb(II) removal ability of the two biosorbents and the investigated factors that affect Pb(II) removal. The results show that the adsorption capacity of xanthate modified corn cob (X–CC) and xanthate modified chestnut shell (X–CS) for Pb(II) is related to pH, reaction time, temperature and initial concentrations of both adsorbent and adsorbate. The adsorption of Pb(II) on X–CC and X–CS follows Langmuir isotherm equation and quasi-secondary kinetic equation, and their fitted qm values are 166.39 and 124.84 mg g−1, respectively. The analysis shows that the biosorbent has high selectivity to Pb(II) rather than Cu(II) and Cd(II), and still maintains a high removal rate of Pb(II) in actual wastewater. The biosorbents remove metal ions mainly through ion exchange reaction and the functional group in the material complexes with the metal to form micro-precipitation. The high adsorption capacity in aqueous solution and low costs in the manufacturing process of the present biosorbents ensure that they have great potential in practical applications for treating heavy-metal contaminated surface water.