Removal Reaction Research Articles

Spectroscopy of Cd98 by two-nucleon removal from In100

Low-lying states of Cd-98 have been populated by the two-nucleon removal reaction (In-100, Cd-98+gamma) and studied using in-beam gamma-ray spectroscopy at the Radioactive Isotope Beam Factory at RIKEN. Two new gamma transitions were identified and assigned as decays from a previously unknown state. This state is suggested to be based on a pi 1g(/9/2)(-1)2p(1/2)(-2) configuration with J(pi) = 5(-). The present observation extends the systematics of the excitation energies of the first 5(-) state in N = 50 isotones toward Sn-100. The determined energy of the 5(- )state in Cd-98 continues a smooth trend along the N = 50 isotones. The systematics are compared with shell-model calculations in different model spaces. Good agreement is achieved when considering a model space consisting of the pi(1f(5/2), 2p(3/2), 2p(1/2), 1g(9/2)) orbitals. The calculations with a smaller model space omitting the orbitals below the Z = 38 subshell could not reproduce the experimental energy difference between the ground and first 5(-) states in N = 50 isotones, because proton excitations across Z = 38 subshell yield a large amount of correlation energy that lowers the ground states. (Less)

The Effect of pH on Removal of Phosphate from Water Using Aluminum Electrodes by Electrocoagulation Method

: In this study, the effect of wastewater pH on phosphate removal by electrocoagulation method using aluminum plate electrodes was investigated. For this purpose, experiments were carried out at initial pH values ranging from 3-10, and the effect of the initial pH of the wastewater on phosphate removal efficiency, energy consumption and reaction rate was analyzed. From the results obtained, it was determined that the initial pHs of the optimum wastewater was 3 and 4. Because at low pH, both phosphate removal efficiency is high and the energy consumption of the system is low. While 97% removal efficiency is reached in 20 minutes at pHi=3, it increases in this period with the increase of the wastewater initial pH. These data show that the removal rate is higher at lower initial pHs. While the 1st degree reaction rate constant at pHi=3 is k1=0.2154 min-1, this value decreases to k1=0.071 min-1 at pHi=10. At pHi=3, the energy consumption of the system has been determined as 0.553 kWh m-3 in 12 minutes of contact time. In addition, in the measurements made during the trials, it was observed that the highest PO4-P removal occurred during the period when the pH of the system was between 5-7.

The Air Over There: Exploring Exoplanet Atmospheres

The atmospheric composition for a rocky exoplanet will depend strongly on the planet’s bulk composition and orbital position. Nontraditional gases may be present in the atmospheres of exceptionally hot planets. Atmospheres of more clement planets will depend on the abundance of volatiles acquired during planet formation and atmospheric removal processes, including escape, condensation, and reaction with the surface. To date, observations of exoplanet atmospheres have focused on giant planets, but future space-and ground-based observatories will revolutionize the precision and spectral resolution with which we can probe an exoplanet’s atmosphere. This article consolidates lessons learned from the study of giant planet atmospheres, and points to the observations and challenges on the horizon for terrestrial planets.

Using a sulfur autotrophic fluidized bed reactor for simultaneous perchlorate and nitrate removal from water: S disproportionation prediction and system optimization.

The sulfur autotrophic reduction (SAR) process is promising in co-reduction of perchlorate and nitrate from aqueous solution. To further understand the reaction process, we developed a sulfur autotrophic fluidized bed reactor where the proceeding extent of sulfur (S) disproportionation was predicted by Response surface methodology (RSM) for the first time. Three fundamental reaction parameters including the hydraulic retention time (HRT), co-existing nitrate concentration ([Formula: see text]) and recirculation ratio (R) were considered for reactor optimization. The results demonstrated that S disproportionation was promoted by long HRT and high R, whereas was inhibited by high [Formula: see text]. Also, the optimal HRT, [Formula: see text] and R were 0.50h, 10.00mg/L and 14, respectively, the bioreactor can achieve high reduction efficiency of perchlorate and nitrate (> 98.45%), and generate less sulfate (236.07mg/L). High-throughput sequencing showed that Chlorobaculum was related to S disproportionation, and Sulfurovum was associated with nitrate/perchlorate reducing. All results indicate that the sulfur autotrophic fluidized bed reactor is a promising candidate for the treatment of perchlorate and nitrate wastewater in future practical applications.

The Fenton-like reaction for Arsenic removal from groundwater: Health risk assessment

In this paper, the heterogeneous Fenton like-reaction for Arsenic-contaminated groundwater remediation based on the performance of FeSO4 as an efficient and green catalyst and CaO2 as a source of H2O2 was investigated. To intensify the heterogeneous Fenton process, three oxidants were tested: sodium percarbonate (SPC), sodium persulfate (SPS), and calcium peroxide (CP). The results showed that CP and SPC had a synergetic effect on the rate of Arsenic degradation, while SPS had an antagonistic effect. On the other hand, inorganic ions such as Na+, Mg2+ have a very low impact on the Arsenic removal efficiency, while the anions Cl− and NO3− exhibited significant inhibition of Arsenic degradation. This effect may be imputed to the reaction and conversion of hydroxyl (HO•) radicals to less reactive. Thus, HCO3− and humic acid dramatically raised the degradation rate. Also, the response Surface method based on Box-Behnken design was applied to examine the suitable modeling, and optimized condition of the Fenton like-reaction process, the maximum Arsenic removal efficiency of 94.91% is obtained when [Fe3+]0 = 1.97 mM, [CaO2]0 = 1.74 mM and initial pH = 4.67. The obtained results showed that the Fenton-like reaction is an effective and reliable process for arsenic removal from groundwater with low non-carcinogenic risk (HQ) and carcinogenic risk (CR) values.

The treatment of electroplating wastewater using an integrated approach of interior microelectrolysis and Fenton combined with recycle ferrite

Heavy metal ions in chelated forms have aroused great concerns because of their high solubility, poor biodegradation and extreme stability. In this research, an efficient strategy, interior microelectrolysis-Fenton-recycle ferrite (IM-Fenton-RF), was developed to treat simulated electroplating wastewater containing chelated copper at room temperature. The decomplexation of chelated copper was carried out by both interior microelectrolysis and Fenton reactions. IM process can not only partly degrade the complexes of chelated copper via the microelectrolysis reaction but also it produces Fe2+ ions for the Fenton reaction. After decomplexation, the IM-Fenton effluent directly flowed into the RF reactor for copper ions removal. Under optimum reaction conditions (reflux ratio = 0.37, Fe2+ concentration = 9.20 g/L at pH 10.18), 99.9% copper was removed by the IM-Fenton-RF system. The produced IM-Fenton-RF sludge is based on ferrite precipitate and has several advantages over metal hydroxides sludge. Ferrite sludge is stable owing to the stability of ferrite's crystal structure, while the toxicity characteristic leaching procedure (TCLP) test meets relevant standards. The sedimentation rate and volume of ferrite sludge were 3.86 times faster and 11.0 times lower than those of metal hydroxides sludge. Furthermore, the yielding sludge of ferrite can be recovered and utilized for the synthesis of Fe–C metallic species, the main compound of IM packing for interior microelectrolysis reaction. All these results show that a combination of IM-Fenton and RF is an effective approach to treat wastewater containing chelated copper, showing great potential for industrial applications.

Enhancing autotrophic nitrogen removal with a novel dissolved oxygen-differentiated airlift internal circulation reactor: Long-term operational performance and microbial characteristics

Autotrophic nitrogen removal (ANR) processes have not been widely applied in wastewater treatment due to their long start-up time and unstable performance. In this study, a novel dissolved oxygen-differentiated airlift internal circulation reactor was developed to enhance ANR from wastewater. During 200 days of continuous operation, the reactor start-up was achieved within 30 days; a high total nitrogen removal efficiency of 80% was achieved and stably maintained under an aeration rate of 0.90 L/min and hydraulic retention time of 6 h. Additionally, the color of sludge went from a light yellow to dark red, and the amount and size of the micro-granules increased obviously. Medium-sized (1.0–2.5 mm) micro-granules accounted for 72.4% on day 190. The specific anammox activity increased from 0.53 to 1.43 g-N/g-VSS/d, while the SNOA decreased from 0.93 to 0.08 g-N/g-VSS/d. Furthermore, the microbial analysis showed that the Nitrosomonas (4.2%) and Candidatus Brocadia (22.6%) were enriched and formed the micro-granules after the reactor's long-term operation. The results indicate that novel configuration realizes the partitioning of dissolved oxygen (DO), optimizes nitritation and anammox reactions, and accelerates biochemical reactions, thereby enhancing ANR performance. This study provides a practical alternative to enhance ANR performance and a scientific basis for the development and application of novel nitrogen removal reactors.

Efficacy of a novel electrochemical membrane-aerated biofilm reactor for removal of antibiotics from micro-polluted surface water and suppression of antibiotic resistance genes

An electrochemical membrane-aerated biofilm reactor (EMABR) was developed for removing sulfamethoxazole (SMX) and trimethoprim (TMP) from contaminated water. The exertion of electric field greatly enhanced the degradation of SMX and TMP in the EMABR (~60%) compared to membrane-aerated biofilm reactor (MABR, < 10%), due to the synergistic effects of the electro-oxidation (the generation of reactive oxygen species) and biological degradation. Microbial community analyses demonstrated that the EMABR enriched the genus of Xanthobacter, which was potentially capable of degrading aromatic intermediates. Moreover, the EMABR had a lower relative abundance of antibiotic resistance genes (ARGs) (0.23) compared to the MABR (0.56), suggesting the suppression of ARGs in the EMABR. Further, the SMX and TMP degradation pathways were proposed based on the detection of key intermediate products. This study demonstrated the potential of EMABR as an effective technology for removing antibiotics from micro-polluted surface water and suppressing the development of ARGs.

Study on the Mechanism of Selective Catalytic Reduction of NOx by NH3 over Mn-Doped CoCr2O4

In this paper, the first-principles calculation method based on density functional theory is used to calculate the structure of CoCr2O4 and Mn-doped Mn0.1Co0.9Cr2O4 low-refractive-index surface (100) and the adsorption model of NH3 and other molecules. Moreover, the process of the NOx removal reaction with NH3 was studied in detail. The results showed that the adsorption energy of NH3 and the amount of Mulliken charge transfer increased after Mn doping. The projected density of states indicates that the interactions between the adsorbed molecule and the substrate are stronger. It is worth noting that the doped Mn sites are also favorable sites for catalytic reactions. Based on the calculation results, we know that NH3 molecules are easily adsorbed on the surface of the catalyst and then dehydrogenated to produce NH2, NH, and other products. The next major step is the reaction of NH2 with gaseous NO to form an intermediate product of NH2NO, which is then decomposed into N2 and H2O. However, the route of N2O as an intermediate is energetically infeasible. Among them, NH3 dehydrogenation is a rate-determining step, and the activation energy barrier is 1.01 eV. However, under aerobic conditions, the activation energy barrier (0.71 eV) from NH3 to NH2 is significantly reduced. In addition, the adsorbed NO reacts with the active O atoms to generate NO2 on the surface, and NO2 can undergo a “fast selective catalytic reduction” process. To sum up, doping manganese on the surface of the CoCr2O4 catalyst can improve the catalytic activity of denitration, and the Mn0.1Co0.9Cr2O4 catalyst has a good selectivity.

Combining plug-in devices for reconfigurable removal of trichloroethylene and heavy metal ion in aqueous solution: Application and biosafety of iron-iron sulfide and its composites

The development of artificial intelligent (AI) planning for smart water treatment and the exploration of digitizable continuous-flow fabrication platform comprising electrically operable reactions for reconfigurable contaminant removal are two important challenges in future water purification technology. Most research and development efforts as well as the investment in water purifying materials have been focusing on the dimensions, compositions, or architectures containing highly adsorptive and catalytic components for effective combinatorial contaminant removal. However, limited attempts have been made to secure a digital system for adjusting the supply of existing adsorbents and chemicals to respond to transient or nonuniform distribution of contaminant load. To utilize AI planning in a more practical manner, developing a plug-in platform is necessary for reconfigurable fabrication that enables in situ supply of different water purifying materials. Therefore, a platform suitable for handling different material architectures was constructed by selecting different operation modes of plug-in reactionware (spark ablation, droplet generation, and photon supply) to modulate the architectures of water purifying materials. First, iron-iron sulfide (Fe–FeS) was fabricated using Fe nanoparticles and thiol vapors under photoirradiation, followed by combining the resulting Fe–FeS with metal (cobalt, nickel, or palladium) nanoparticles or graphene nanosheets to enhance the trichloroethylene (from 0.135 to 0.221 h−1 in removal kinetics) or heavy metal ion (from 299 to 592 mg g−1 in adsorption capacity) removal. Finally, in vitro toxicological analyses were conducted to determine biosafety of the resulting materials. The results of cell viability and reactive oxygen species profiles indicated that further investigation is required to realize the safe-by-design concept.

Efficient mercury removal in chlorine-free flue gas by doping Cl into Cu2O nanocrystals

The low content of hydrogen chloride (HCl) in flue gas is difficult to meet the request of Hg0 removal. Here, a small amount of Cl was doped into the crystal lattice of Cu2O nanocrystals (Cl-Cu2O), presenting excellent Hg0 removal efficiency in chlorine-free coal combustion flue gas. SEM, XRD, BET, and XPS characterizations revealed well crystal morphology and structure of Cl-Cu2O catalyst. Besides, Cl-Cu2O had smaller sizes and higher BET surface area compared with Cu2O. Hg0 removal behaviors were studied using a lab-scale fixed-bed reactor. After doping Cl, Hg0 removal efficiency was improved obviously and could reach nearly 100% above 150 ℃, indicating chlorine incorporated into the catalyst lattice had a better role for Hg0 removal. Besides, gas composition effect on Hg0 removal was analyzed. Cl-Cu2O had high sulfur resistance capacity, and Hg0 removal efficiency can still reach above 90% even at 2000 ppm SO2. O2 played a critical role in the Hg0 removal reaction. Furthermore, a plausible mechanism for Hg0 removal was analyzed. Doping Cl into the lattice of Cu2O nanocrystals was beneficial for the activation of molecular oxygen, and generated reactive oxygen species can further activate Cl to participate in the Hg0 removal reaction.

Detailed study of the eikonal reaction theory for the breakup of one-neutron halo nuclei

Background: One-neutron removal reactions are used to study the single-particle structure of unstable nuclei, and in particular the exotic halo nuclei. The Eikonal Reaction Theory (ERT) has been developed by Yahiro, Ogata and Minomo in Prog. Theor. Phys. 126, 167 (2011) to include dynamical effects, which are missing in the usual eikonal description of these reactions. Encouraging results have been obtained for total breakup cross sections in comparison to more elaborate reaction models. Purpose: We extend these comparisons to more differential breakup cross sections expressed as functions of the relative energy or parallel momentum between the core and halo neutron. Method: ERT predictions of these cross sections are compared to state-of-the-art calculations. Results: The hypotheses upon which the ERT is based are confirmed and their range of validity is made clearer. The actual ordering of the evolution operators {affects ERT differential} cross sections and a specific choice leads to excellent agreement with the reference calculation. Dynamical effects in the treatment of the neutron-target interaction can be significant in the parallel-momentum observable. Conclusions: The role of the different interactions in the dynamics of breakup reactions of one-neutron halo nuclei are better understood and improvements to the ERT are suggested.

Adsorption and Photocatalytic Activity of Nano-magnetic Materials Fe3O4@C@TiO2-AgBr-Ag for Rhodamine B

Background: TiO2 nanoparticles possess adsorption capacity and photocatalytic activity, and are thus fitted for removal of dyes from water. However, TiO2 nanoparticles are difficult to separate from the bulk solution due to high loss. Moreover, TiO2 can only use light with a wavelength of less than 387.5 nm, so the utilization efficiency of solar energy is very low. The present work prepared Fe3O4@C@TiO2-AgBr-Ag composites to overcome the shortcomings of TiO2. Objective: Adsorptive and photocatalytic performance of nano-magnetic materials Fe3O4@C@TiO2- AgBr-Ag. Methods: Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag magnetic nanocomposites were prepared by the sol-gel method. Their structure was characterized. Performances of Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag for removing Rh B were thoroughly investigated and compared. Langmuir– Hinshelwood kinetic model was applied to analyze the heterogeneous processes of adsorption and photodegradation. Results: Removal experiments were carried out with Rhodamine B as the subject. The effects of contacting time, pH, subject concentration, and doses of photocatalyst on the removal performance were studied. The removal of Rh B by Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag involved both adsorption and photodegradation, and the photocatalytic activity of Fe3O4@C@TiO2-AgBr-Ag was much higher than that of Fe3O4@C@TiO2. The optimum removal conditions were determined. Under the optimal conditions, the removal rate of Rhodamine B with Fe3O4@C@TiO2 was 77.8%, and the removal rate of Rhodamine B with Fe3O4@C@TiO2- AgBr-Ag was 87.3%. Conclusion: The coupling of the nanostructured metal Ag to the outer surface of TiO2 could effectively increase photocatalytic efficiency under visible light. The photocatalysts could be separated from bulk solutions by using a magnet and be easily recycled. The removal reaction kinetics fitted with the first-order model.

Simultaneous removal of elemental mercury and NO from flue gas by the CeO2/TiO2 catalysts and the mechanism investigation

AbstractMercury pollution has become one of the high‐profile environmental problems in the world. A series of CeyTi catalyst were synthesized by sol–gel method, and the process of simultaneous conversion of NO and removal of mercury (Hg0) in the flue gas was studied. BET, SEM, and XRD were used to systematically detect the physicochemical properties of the catalysts, which show that excessive Ce loading would make its specific surface area reduce. The NO conversion efficiency would increase with the increase of the Ce loading. The optimal Ce/Ti mass ratio was 0.3. A part of the adsorbed NO would be oxidized by the active oxygen species on the catalyst surface to produce a certain amount of nitrogen‐containing substances, such as NO+, NO3−, or NO2. The produced substances could promote the adsorption and oxidation of Hg0. The NO conversion was very dependent on the oxygen in the flue gas. The activity of the Ce0.3Ti catalyst was promoted in the presence of O2. SO2 and H2O would inhibit the reaction of NO conversion and Hg0 removal. The mechanisms of the catalytic system have been proved via the Mars‐Maessen mechanism.

Application of TiO2/ZnFe2O4/glycine nanocatalyst to the treatment of methyl orange dye from aqueous solution: Impacts of dissolved mineral salts on dye removal efficiency

This study aimed to remove one of the frequently used dyes in textile industries, Methyl Orange, from pollutant water with TiO2/ZnFe2O4/Glycine nanocatalyst under UV irradiation. The TiO2/Glycine/ZnFe2O4 nanocatalyst was synthesized through the sol-gel method and characterized by XRD, XRF, FT-IR, UV-Visible DRS, BET, FE-SEM, and EDX analyses. Process factors, including initial dye concentration (10-30 ppm), nanocatalyst dosage (0.5-1.5 g/L), initial pH solution (3-11), and irradiation time (30-150 min), were investigated by central composite design. The removal efficiency of Methyl Orange was 80% under optimal conditions (dye concentration: 20 ppm, nanocatalyst dosage: 1 g/L, irradiation time: 120 min, and pH=6.5). The effects of mineral salts such as NaHCO3, NaCl, Na2SO4, KCl, MgSO4, and CaCl2 with the concentrations of 50-800 ppm on the dye removal efficiency were examined under the optimal conditions. Low concentrations of NaCl, KCl, and CaCl2 had adverse effects on MO removal efficiency, while the dye removal efficiency raised at their high levels (RNaCl.800=74.52%). An increase in concentrations of MgSO4 and Na2SO4 led to deactivation effects on the dye removal efficiency and reaction rate constant (MgSO4 deactivation: 36%). There was an upward trend in the pollutant removal efficiency and reaction rate constant using NaHCO3 (RNaHCO3.800=82.4% and kNaHCO3.800=20.84 day-1).

Visible light excited graphitic carbon nitride for efficient degradation of thiamethoxam: Removal efficiency, factors effect and reaction mechanism study

In this decade, photocatalytic degradation of organic contaminants has attracted great attentions. In this study, we used graphic carbon nitride (g-C3N4) nanosheets as the photocatalyst for the degradation of thiamethoxam (THM). The properties of g-C3N4 nanosheets have been fully characterized by the analysis techniques. The experiments results shown that under the optimum condition, 91.3% of THM degradation efficiency can be reached in the presence of g-C3N4 nanosheets within 60 min under visible light irradiation. Take the realistic application into consideration and to fully investigate the reaction process, the influence of reaction parameters, including the dosage of g-C3N4 nanosheets, initial THM concentration, and initial solution pH value, co-existence ions, humic acid (HA) and fulvic acid (FA) have been systematically studied and discussed. Results demonstrated that weak acidity and neutral condition is benefit for THM decomposition, and Ca2+ and Mg2+ present enhanced inhibition effect than Na+ for THM removal. Meanwhile, PO43- and CO32- show strong inhibition effect, but HA and FA performed weak inhibitory effect. The trapping experiments and electron spin resonance (ESR) measurement demonstrated that superoxide radical (•O2-), hydroxyl radical (•OH) and holes (h+) are all generated during the reaction process. There are all participated in the THM decomposition process and •O2- plays the major role on it. The results obtained in this study indicated that metal free g-C3N4 present great photocatalytic activity and stability for THM removal and owns great potential in the application of actual agricultural environment.

Evaluation of anaerobic and anoxic reactors installed in serial to treat fish tank effluent

Effluent from a fish tank with Nile tilapia (Oreochromis niloticus) was treated in a system of two parallel fixed-bed anaerobic reactors followed by a suspended stirred, anoxic reactor for solids, organic matter and nitrogen removal. Microbial community structure was compared between the reactors and an enriched anammox culture originated from anaerobic sludge by using the PCR (Polymerase Chain Reaction) and DGGE (Denaturing Gradient Gel Electrophoresis) techniques. DGGE analysis revealed three large microbial clusters, namely, the biomass in the inoculum, the biomass growing in the reactors, and the enriched anammox culture. The similarity between the microbial community recovered from the anaerobic reactors and the anammox community was considered low (32.7%), suggesting differentiation of the bacterial community as a function of the selection of specific anammox groups. The last step in the anoxic reactor had worsened the effluent quality. The potential of organic matter and ammonia removal in a single anaerobic reactor was demonstrated.

Preparation and Evaluation of Iron-Based Catalysts from Corncob for NO Reduction

ABSTRACT This paper presents a one-step method that significantly simplifies the biomass carbonization preparation with Fe0 as active catalyst. The catalyst activity was compared to that of the catalyst prepared by a two-step method using a fixed-bed reactor for NO removal. The effects of temperature on catalyst preparation and that of SO2 on catalyst activity were also studied. The active species and surface structures of the catalysts were determined using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis-mass spectrometry (TGA-MS), and CO temperature-programmed reduction (CO-TPR), respectively. Fe0 and Fe3C were the active catalytic species during NO removal. The catalysts prepared by the one-step method had a higher NO removal ability than that of the catalyst prepared by the two-step method. This was attributed to the small particle sizes of Fe0 and Fe3C as well as their high selectivity and anti-sintering characteristics. The catalyst prepared at 800°C exhibited the highest catalytic activity because of the special morphology. Catalyst deactivation was caused by oxidation of low-valence iron to Fe3O4 by NO, which was accompanied by agglomeration and sintering. Low SO2 concentrations affected the catalyst activity during NO removal.

Cu–Fe embedded cross-linked 3D hydrogel for enhanced reductive removal of Cr(VI): Characterization, performance, and mechanisms

Porous hydrogel, as a high-efficiency adsorbent for heavy metals, suffers the drawbacks of the use of expensive and toxic reagents during the process of preparation, further limiting its application ranges. Besides, the heavy metals couldn't be transformed into nontoxic species, which leads to the environmental pollution risk. Herein, a three-dimensionally (3D) structured Cu–Fe embedded cross-linked cellulose hydrogel (nFeCu-CH) was innovatively fabricated by a novel self-assembly and in-situ reduction method, which exhibited exceptionally enhanced adsorption-reduction property towards Cr(VI) wastewater. The results of degradation experiment exhibited that the removal reaction followed Langmuir-Hinshelwood first order kinetic model and the degradation rate constant decreased with solution pH and initial Cr(VI) concentration, while increased with nFeCu-CH dosage and temperature. Regeneration studies demonstrated that more than 88% of Cr(VI) was removed by nFeCu-CH even after five times of cycling. nFeCu-CH exhibited excellent reductive activity, which had a close connection with the superiority of 3D crosslinked architectures and bimetallic synergistic effect. And 97.1% of Cr(VI) could be removed when nFeCu-CH dosage was 9.5 g/L, pH was 5, initial concentration of Cr(VI) was 20 mg/L and temperature was 303 K. Combined with cellulose hydrogel not only could provide additional active sites, but also could restrain the crystallite growth and agglomeration of nano-metallic particles, leading to the promotion of Cr(VI) removal. In addition, coating with Cu facilitated the generation and transformation of electrons according to the continuous redox cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I), leading to the further improvement of the reductivity of nFeCu-CH. Multiple interaction mechanisms including adsorption, reduction and co-precipitation between nFeCu-CH and Cr(VI) were realized. The current work suggested that nFeCu-CH with highly reactive sites, excellent stability and recyclability was considered as an potential material for remediation of Cr(VI) contaminated wastewater.

Compositional effects of clay-fly ash geopolymers on the sorption process of lead and zinc.

Because long-term leachate penetration through a hydraulic barrier is unavoidable, active-passive liners are widely used to mitigate the migration of potential contaminants. Geopolymerization represents a viable method for metals removal, which simultaneously improves the properties of local clay to compensate for the lack of suitable soil in the design of active-passive liners. This study investigated how clay-fly ash geopolymers enhance the sorption of divalent lead [Pb(II)] and divalent zinc [Zn(II)] from leachate compared with an untreated clay. Two clay-fly ash geopolymers were synthesized from the mixtures containing 50 and 60% fly ash to the total solid mass and then activated by 10M NaOH solutions. The influence of Na/fly ash ratios and activator content was also examined. The results indicate that a fly ash-based geopolymer could be a simple solution to increase the sorption capacity of local clay. A lower ratio of Na/fly ash and activator content, resulting in a higher porosity, led to a better performance for metal removal. According to the results of sorption isotherms and batch experiments, Pb(II) and Zn(II) exhibit different sorption behaviors affected by the compositions of synthesized clay-fly ash geopolymers, which could be adjusted to reach a proper sorption capacity. The results of the kinetic study also show that the heterogeneous matrix of the clay-fly ash geopolymers with different porosities led to mutual cooperation between reaction and diffusion-controlled steps for metal removal.