Application of a novel polymer cross-linked with magnetite for efficient norfloxacin adsorption at a wide pH range.

Nowadays, NOR-containing wastewater has placed huge pressure on global ecology. In this study, a chemically-modified chitosan-based polymer was cross-linked with magnetite to prepare a novel magnetic composite adsorbent named Fe3O4/CS-P(AM-SSS) for norfloxacin (NOR) removal. The preparation conditions were optimized by single factor experiments and response surface methodology. A series of characterization analyses were carried out on the morphology, structure, and properties of Fe3O4/CS-P(AM-SSS), verifying that Fe3O4/CS-P(AM-SSS) was successfully prepared. Batch adsorption experiments showed that NOR was efficiently removed by Fe3O4/CS-P(AM-SSS), with a broad pH applicability of 3-10, short adsorption equilibrium time of 60 min, maximum adsorption capacity of 268.79 mg/g, and high regeneration rate of 86% after eight adsorption-desorption cycles. Due to the three-dimensional network structure and abundant functional groups provided by modified chitosan polymer, the superior adsorption capability of Fe3O4/CS-P(AM-SSS) was achieved through electrostatic interaction, π-π stacking, hydrophobic interaction, and hydrogen bonding. Adsorption process was exothermic and well fitted by the pseudo-second-order kinetic model and the Langmuir isothermal model. The presence of cations had a slight inhibitory effect on NOR adsorption, while humic acid nearly had no effect. In model swine wastewater, 90.3% NOR was removed by Fe3O4/CS-P(AM-SSS). Therefore, with these superior characteristics, Fe3O4/CS-P(AM-SSS) was expected to be an ideal material for treating NOR-containing wastewater in the future.

Effects of operational sex ratio, mating age, and male mating history on mating and reproductive behavior in Grapholita molesta.

The short-lived polygamous moth Grapholita molesta (Busck) is an important fruit pest worldwide. Trapping males by synthetic female sex pheromones is not an effective reproductive control strategy. It is important to improve this technology by understanding the mating system of G. molesta. This study investigated mating opportunities and fertile egg production by altering the operational sex ratio, mating age, and male mating history in repeated single mating and multiple mating in the two sexes. Our results showed that the mating and reproductive parameters of virgin males were affected by the number and age of virgin females. Males preferred a female number ≤three-fifths of the male number or ≤2-day-old females, while they discriminated against a female number ≥three times of the male number or ≥5-day-old females. On the other hand, the mating and reproductive parameters of virgin females were affected by repeated single mating and especially multiple mating under different male mating histories. Females preferred once-mated males and discriminated against virgin males. These results indicated that mating systems including more and older virgin females for virgin males and different virgin males for virgin females may be suitable for suppressing G. molesta populations. Hence, these results revealed that preventing mating of virgin adults by synthetic female sex pheromones should be most effective in controlling G. molesta.

Effective elimination of Hg(II) from water bodies with acid-modified magnetic biomass spent coffee grounds: conditional optimization and application.

To maximize the efficiency of biomass waste utilization and waste management, a novel acid-modified magnetic biomass spent coffee grounds (NiFe2O4/SCG) was obtained by pyrolysis at 473 K and co-precipitation methods and employed to eliminate bivalent mercury (Hg(II)) in water bodies. The prepared NiFe2O4/SCG adsorbent exhibits remarkable magnetism with a strength of 45.78 emu/g and can easily be separated from water via a magnetic force. The adsorption of Hg(II) over the NiFe2O4/SCG has an optimal conditions of pH = 8, T = 39 ℃, and dosage of 0.055 g/L, and the maximal adsorption capacity for Hg(II) is 167.44 mg/g via Response Surface Methodology optimization. The removal of Hg(II) over NiFe2O4/SCG primarily involves ion exchange, electrostatic attraction, and chelation; conforms to the pseudo-second-order kinetic and Langmuir models; and is an endothermic reaction. Additionally, the magnetic biomass NiFe2O4/SCG has good regeneration capability and stability. The application research reveal that inorganic salt ions, nitrogen fertilizer urea, humus, and other contaminants in different actual water bodies (river water, lake water, and the effluent of sewage treatment plant) have little effect on the adsorption of Hg(II) over the NiFe2O4/SCG. The prepared adsorbent NiFe2O4/SCG has practical application value for removing Hg(II) from water bodies.

Photocatalytic activity evaluation of polyvinylpyrrolidone K30 assisted synthesis of 1D oxygen-vacancy-rich Bi5O7BrxI1-x nanorod solid solution.

The unique layered structure of bismuth halide oxide has led to an extensive application in the degradation of refractory antibiotics from water environments. With the aid of regulating the energy band structure of photocatalytic materials and equilibrating the response towards visible light and redox ability, a novel oxygen-vacancy-rich Bi5O7BrxI1-x nanorod solid solution was synthesized by polyvinylpyrrolidone K30 assisted solvothermal method, and its photocatalytic behavior was investigated for the degradation of antibiotic levofloxacin under visible light. The degradation rate of the optimal Bi5O7Br0.5I0.5 to levofloxacin can reach 82.7% within 30 min, which is 9.22 and 4.74 times higher than those of the monomers Bi5O7Br and Bi5O7I. The catalyst of Bi5O7Br0.5I0.5 shows 99.88% antibacterial activity against Escherichia coli. The efficient photocatalytic ability of the Bi5O7Br0.5I0.5 is resulted from the alteration of energy band structure and suppression of charge recombination due to benign changes in the electronic and crystal structures. Furthermore, both various characterizations and Density Functional Theory calculations reveal that a multitude of oxygen vacancies exist in the Bi5O7Br0.5I0.5. The photocatalytic degradation pathways were explored and the toxicity of the intermediates was also appraised. The present work provides a mild and feasible construction of solid solutions and introduction of oxygen vacancies to eliminate environmentally refractory organic pollutants with photocatalytic technology.

Removal of Hg(II) with MgAl-layered double hydroxide functionalized by schiff base ligands: Application and condition optimization.

To effectively remove heavy metal Hg(II) from water bodies, a novel adsorbent of MgAl-layered double hydroxide (LDH) was designed and functionalized with Schiff base. The characterization results of the adsorbent (MgAl-LDH@SiO2-AG) show that the Schiff base polymer was successfully coated onto the outside surface of MgAl-LDH with hexagonal structure. The theoretical maximum adsorption capacity to Hg(II) is 228.46 mg/g at pH 7 and 298 K. The different pH solutions were investigated from pH 2 to 8, and the optimal capacity of MgAl-LDH@SiO2-AG toward Hg(II) achieves 268.7 mg/g at pH = 7.2, T = 36.8 °C, C0 = 32.1 mg/L and dosage = 0.083 g/L. In reality, the adsorbent not only exhibits efficient removal of Hg(II) in various water bodies, including lake water, river water, effluent from sewage treatment plant, but also has an excellent selectivity in electroplating wastewater containing different heavy metal ions. Low contents of TN and TP in real wastewater have less effect on the removal of Hg(II). Moreover, the prepared adsorbent had a good reusability and stability. The reaction mechanism mainly involves chelation with nitrogen/oxygen-containing groups and the predominant participation of nitrogen atoms in the Schiff base functional group. The removal of Hg(II) relies on the pseudo-second-order kinetics and Langmuir model, and is an endothermic and spontaneous chemical reaction. The present work offers a practical method for preparing highly effective adsorptive materials with the LDH composites and for the treatment of heavy metal Hg(II) from water bodies.

High selective removal towards Hg(II) from aqueous solution with magnetic diatomite-based adsorbent functionalized by poly(3-aminothiophenol): conditional optimization, application, and mechanism.

A novel diatomite-based (DMT) material was obtained by post-functionalization of DMT/CoFe2O4 with 3-aminothiophenol and applied to remove Hg(II) ions from aqueous solution. The obtained adsorbent of DMT/CoFe2O4-p-ATP was detected by various characterization means. The optimization of response surface methodology reveals that magnetic diatomite-based material of DMT/CoFe2O4-p-ATP has an optimal adsorption capability of 213.2 mg/g towards Hg(II). The removal process of Hg(II) is fitted well to pseudo-second-order and Langmuir models, respectively, indicating that the adsorption process is controlled by monolayer chemisorption. DMT/CoFe2O4-p-ATP exhibits superior affinity towards Hg(II) through electrostatic attraction and surface chelation, compared with other coexisting heavy metal ions. Meanwhile, the prepared adsorbent DMT/CoFe2O4-p-ATP displays excellent recyclability, good magnetic separation performance, and satisfying stability. The as-prepared diatomite-based DMT/CoFe2O4-p-ATP can be a promising adsorbent for mercury ions.

Optimal preparation of a core-shell structural magnetic nanoadsorbent for efficient tetracycline removal.

As emerging contaminants, tetracyclines pose a severe threat to aquatic environments and human health. Therefore, developing efficient approaches to remove tetracyclines from water has attracted a large amount of interest. Herein, a novel core-shell structural magnetic nanoadsorbent (FSMAS) was facilely prepared by graft copolymerization of acrylamide (AM) and sodium p-styrene sulfonate (SSS) monomers on the surface of vinyl-modified Fe3O4@SiO2 (FSM). From single factor experiments, the optimal graft copolymerization conditions were concluded to be the following: initiator concentration = 1.2‰, reaction pH = 9, monomer molar ratio = 7 : 3. The surface morphology, microstructure and physicochemical properties of as-prepared FSMAS were fully evaluated by different characterization techniques, including SEM, TEM, FTIR, XPS, XRD and VSM. The adsorption performance of FSMAS towards tetracycline hydrochloride (TCH) was systematically studied by batch adsorption experiments. Results showed that the adsorption capability of the adsorbent was largely enhanced after graft copolymerization. The removal rate of TCH by FSMAS reached 95% at solution pH = 4.0, almost 10 times higher than FSM. Besides, the adsorption process of TCH by FSMAS was very efficient, 75% of pollutant could be adsorbed after only 10 minutes, attributed to the stretch of polymer chains and the strong affinity provided by abundant functional groups. Furthermore, TCH-loaded FSMAS was easily regenerated with HCl solution, the regeneration rate was higher than 80% after five adsorption-desorption cycles. Superior adsorption capability, fast solid-liquid separation speed and satisfactory reusability demonstrated the great potential of FSMAS in practical tetracycline removal.

Selective adsorption of Hg(ii) with diatomite-based mesoporous materials functionalized by pyrrole-thiophene copolymers: condition optimization, application and mechanism.

A novel diatomite-based mesoporous material of MCM-41/co-(PPy-Tp) was prepared with MCM-41 as carrier and functionalized with the copolymer of pyrrole and thiophene. The physicochemical characteristics of the as-prepared materials were characterized by various characterization means. The removal behaviour of Hg(ii) was adequately investigated via series of single factor experiments and some vital influence factors were optimized via response surface methodology method. The results exhibit that diatomite-based materials MCM-41/co-(PPy-Tp) has an optimal adsorption capability of 537.15 mg g-1 towards Hg(ii) at pH = 7.1. The removal process of Hg(ii) onto MCM-41/co-(PPy-Tp) is controlled by monolayer chemisorption based on the fitting results of pseudo-second-order kinetic and Langmuir models. In addition, the adsorption of Hg(ii) ions onto MCM-41/co-(PPy-Tp) is mainly completed through forming a stable complex with N or S atoms in MCM-41/co-(PPy-Tp) by electrostatic attraction and chelation. The as-developed MCM-41/co-(PPy-Tp) displays excellent recyclability and stabilization, has obviously selective adsorption for Hg(ii) in the treatment of actual electroplating wastewater. Diatomite-based mesoporous material functionalized by the copolymer of pyrrole and thiophene exhibits promising application prospect.

Visible-light-driven 3D Bi5O7I/BiOCl microsphere with enhanced photocatalytic capability: Performance, degradation pathway, antibacterium and mechanism.

It is well known that both of the separation efficiency of photogenerated carriers and the response capability to visible light remarkably affect the photocatalytic performance. In the present work, a 3D microsphere of Bi5O7I/BiOCl heterojunction catalyst was synthetised. The synergy of Bi5O7I and BiOCl not only significantly enhances the transfer rate and separation efficiency of carriers, but also heightens light absorption capacity. As-prepared Bi5O7I/BiOCl (40 wt% BiOCl) has a higher degradation efficiency on doxycycline hydrochloride (DC) (90 min, 83.0%) and super high inhibition rate (90 min, 99.92%) on Escherichia coli under visible light, compared to the two monomers. Pollutants DC is finally decomposed into CO2, H2O and small molecule intermediates by generated h+, •OH and •O2-. The effects of reactive radicals follow the order of •OH radicals > h+ radicals ≫ •O2- and e- radicals. The possible structures of intermediates and four possible degradation pathways involved were also discussed. In addition, As-synthetised Bi5O7I/BiOCl has preferable reusability and excellent chemical stability. Biological toxicity experiments also verify that Bi5O7I/BiOCl is a green and environmentally friendly composite material. This strategy provides a green, low-toxic way for the application of traditional type II heterojunction in the fields of environmental remediation and photocatalysis.

The Evaluation of Construction Dust Diffusion and Sedimentation Using Wind Tunnel Experiment.

A large quantity of particulate matter is generated during construction of civil engineering projects, which has a negative effect on the atmosphere and environment. In order to explore the concentration, distribution and diffusion of particulate matters generated from construction dust with different moisture contents, a wind tunnel experiment was conducted, and the effects of wind speed and moisture content on the inhibition rate, drifting distance and suppression percentage of particulate matters were investigated. The results show that the peak concentration decreases with the increase in moisture content, compared with dry dust; the peak concentrations for 1%, 2% and 3% moisture content are reduced by 37.07%, 39.53% and 65.38%, respectively. The average concentrations in the cross-section decrease with the increase in the moisture content, resulting in an increasing tendency of the particle inhibition rate. The forecast drifting distance decreases with the increase in the moisture content; when the suspension percentage is 1%, the forecast drifting distances of dry dust, 1%, 2% and 3% moisture content are 641.58, 116.08, 19.33 and 3.82 km, respectively, for a 5 m/s wind speed. Considering that an increase in wind velocity will not only decrease the inhibition rate but also increase the drifting distance, the dust suppression method by increasing the moisture content in low and medium wind velocities is applicable. When the limit value of the particle suppression rate within a distance of 50 m is larger than 70%, construction activities are prohibited at any wind velocity for dry and 1% moisture content, and at wind velocities larger than 2 m/s and 4 m/s for 2% and 3% moisture content, respectively.

Significance of RuO2 modified SCR catalyst for elemental mercury oxidation in coal-fired flue gas.

Catalytic conversion of elemental mercury (Hg(0)) to its oxidized form has been considered as an effective way to enhance mercury removal from coal-fired power plants. In order to make good use of the existing selective catalytic reduction of NO(x) (SCR) catalysts as a cobenefit of Hg(0) conversion at lower level HCl in flue gas, various catalysts supported on titanium dioxide (TiO(2)) and commercial SCR catalysts were investigated at various cases. Among the tested catalysts, ruthenium oxides (RuO(2)) not only showed rather high catalytic activity on Hg(0) oxidation by itself, but also appeared to be well cooperative with the commercial SCR catalyst for Hg(0) conversion. In addition, the modified SCR catalyst with RuO(2) displayed an excellent tolerance to SO(2) and ammonia without any distinct negative effects on NO(x) reduction and SO(2) conversion. The demanded HCl concentration for Hg(0) oxidation can be reduced dramatically, and Hg(0) oxidation efficiency over RuO(2) doped SCR catalyst was over 90% even at about 5 ppm HCl in the simulated gases. Ru modified SCR catalyst shows a promising prospect for the cobenefit of mercury emission control.

Gaseous elemental mercury capture from flue gas using magnetic nanosized (Fe3-xMnx)1-δO4.

A series of nanosized (Fe3-xMnx)1-δO4 (x = 0, 0.2, 0.5, and 0.8) were synthesized for elemental mercury capture from the flue gas. Cation vacancies on (Fe3-xMnx)1-δO4 can provide the active sites for elemental mercury adsorption, and Mn(4+) cations on (Fe3-xMnx)1-δO4 may be the oxidizing agents for elemental mercury oxidization. With the increase of Mn content in the spinel structure, the percents of Mn(4+) cations and cation vacancies on the surface increased. As a result, elemental mercury capture by (Fe3-xMnx)1-δO4 was obviously promoted with the increase of Mn content. (Fe2.2Mn0.8)1-δO4 showed an excellent capacity for elemental mercury capture (>1.5 mg g(-1) at 100-300 °C) in the presence of SO2 and HCl. Furthermore, (Fe2.2Mn0.8)1-δO4 with the saturation magnetization of 45.6 emu g(-1) can be separated from the fly ash using magnetic separation, leaving the fly ash essentially free of sorbent and adsorbed Hg. Therefore, nanosized (Fe2.2Mn0.8)1-δO4 may be a promising sorbent for the control of elemental mercury emission.

Conversion of elemental mercury with a novel membrane delivery catalytic oxidation system (MDCOs).

In order to overcome the shortcomings of the traditional catalytic oxidation (TCO) mode for the conversion of the trace level of elemental mercury (Hg(0)) in flue gas, we put forward a novel and unique assembly that integrated membrane delivery with catalytic oxidation systems (MDCOs), which combined the controlled delivery of oxidants with the catalytic oxidation of Hg(0). The results show that the demanded HCl for Hg(0) conversion in the MDCOs was less than 5% of that in the TCO mode, and over 90% of Hg(0) removal efficiency can be obtained in the MDCOs with less than 0.5 mg m(-3) of HCl escaped. Meanwhile, the inhibition of SO(2) to Hg(0) catalytic conversion in the MDCOs was also less significant than in the TCO. The MDCOs have high retainability for HCl, which is quite favorable to Hg(0) conversion and HCl utilization. The reaction mechanism on mercury conversion in the MDCOs is discussed. The MDCOs appear to be a promising method for emission control of elemental mercury.

Synthesis of Magnetic Short-Channel Mesoporous Silica SBA-15 Modified with a Polypyrrole/Polyaniline Copolymer for the Removal of Mercury Ions from Aqueous Solution.

A novel magnetic short-channel mesoporous silica SBA-15 composite adsorbent was prepared by the copolymerization of pyrrole and aniline. The prepared novel nanoadsorbent polypyrrole-polyaniline/CoFe2O4-SBA-15 (PPy-PANI/M-SBA-15) has a significant adsorption effect on heavy metal mercury ions. The batch adsorption experiment was carried out to study the effects of various parameters including solution pH, initial concentration (C 0), adsorbent dose (dosage), temperature (T), and contact time on the adsorption effect. The analysis results of the response surface method (RSM) and central composite design (CCD) show that the importance for adsorption factors is pH > C 0 > T > dosage, and the maximum capacity of PPy-PANI/M-SBA-15 is 346.2 mg/g under the optimal conditions of pH = 6.7, T = 310 K, C 0 = 29.5 mg/L, and a dosage of 0.044 g/L. The pseudo-second-order kinetic model and the Langmuir isotherm model simulate the adsorption behavior of mercury ions. In addition, thermodynamic parameters indicate self-heating and reversible adsorption processes. A covalent bond is formed between the nitrogen-containing functional group and the mercury ions. Excellent magnetic properties and high reproducibility indicate that PPy-PANI/M-SBA-15 has excellent recyclability and environmentally friendly properties and can become a potential heavy metal ion adsorbent in practical applications.

Importance of Preovipositional Period of an Oligophagous Moth in Predicting Host Suitability.

For oligophagous insects, larval performance is very important to evaluate host suitability in host use. However, key indices among all performance traits including survival, development, and fecundity of the adult insect to predict host suitability are not clear. To investigate the key performance indices, we observed the performance of an oligophagous moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a pest mainly damaging rosaceous plants, on three apple varieties, three peach varieties, and three pear varieties in the laboratory by placing its eggs on fruits. The moth's fitness was evaluated by the intrinsic rate of increase at fruit variety- and species-level variability. Our results showed that the preovipositional period of female moths and longevity of male moths were the indices primarily predicting intrinsic rates of increase for fruit variety and for fruit species. However, the preovipositional period of female moths was different at species-level variability but not at variety-level variability, whereas the longevity of male moths was not different at variety- or species-level variability. These results revealed that preovipositional period of female moths was a key predictor for host suitability in G. molesta. This study highlighted that gravid females may be a principal indicator in host resource optimization for oligophagous insects.

Demography of Cacopsylla chinensis (Hemiptera: Psyllidae) Reared on Four Cultivars of Pyrus bretschneideri (Rosales: Rosaceae) and P. communis Pears With Estimations of Confidence Intervals of Specific Life Table Statistics.

The psyllid Cacopsylla chinensis (Yang & Li) (Hemiptera: Psyllidae) is a serious pest of pears in China. To determine and contrast the fitness of the psyllid on two endemic cultivars of Pyrus bretschneideri (i.e., BHXS and BSL) and two introduced cultivars of Pyrus communis (i.e., CB and CRB), we analyzed data on the development, survival, and fecundity from C. chinensis individuals reared on the four cultivars. The age-stage, two-sex life table theory was used in order to enable the inclusion of males in the analysis as well as a means of identifying the variation in developmental durations among individuals. Results indicated that C. chinensis can successfully develop and reproduce on all four pear cultivars. However, based on the lower preadult survival rate, longer preadult duration, longer total preoviposition period (TPOP), and lower fecundity that occurred on both cultivars of P. communis, these two cultivars are less favorable hosts for C. chinensis than the P. bretschneideri cultivars. The lower intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) on CB and CRB pears showed these two introduced cultivars are more resistant to C. chinensis than the endemic BHXS and BSL pears. These resistant cultivars would be appropriate candidates for managing C. chinensis. We used the bootstrap technique to estimate the uncertainty of the population parameters (r, λ, R0, etc.), while also demonstrating that it can be used for estimating the 0.025 and 0.975 percentile confidence intervals of the age of survival rate.

Behavioral effects of different attractants on adult male and female oriental fruit moths, Grapholita molesta.

BACKGROUND: Grapholita molesta (Busck) is a fruit pest worldwide. While sex pheromones-based technology for male attraction has made great progress in the monitoring or mass trapping of G. molesta, the attraction of males alone is not an effective reproductive control strategy. The integration of sex pheromones with female attractants, which have been reported to attract adult females and males, is therefore necessary. To determine a suitable dual-sex attractant for trapping G. molesta, combinations of four attractants [sex pheromones (ph), host-plant volatiles (pp), sugar-acetic acid-ethanol-water solutions (ss), and food lures (fl)] were screened using electroantennograms, wind tunnel experiments, and field trial tests. Various mediums and antioxidants were then added to the selected attractants combination (AC) and examined in the field. RESULTS: The responses of G. molesta to attractants differed significantly between the sexes. Increases in male activation behavior and trapping were motivated by ph, while pp and particularly ss increased adult antennae perception. In response to fl alone or together with ph, more male or female individuals were trapped. This indicates that ph, as a sex lure, and fl, as a host lure, may complete male and female attraction. Consequently, this combination is suggested. In the field trials, the additions of 10 µL of honey and 35% (184.3 µg) of 2,6-di-tert-butyl-4-methylphenol [BTH] (preservatives) to the AC (ph + fl) resulted in moth captures equal to that of a commercial sex pheromones lure. CONCLUSION: A dual-sex attractant composed of ph, fl, honey, and BTH is recommended for trapping G. molesta in the field. © 2020 Society of Chemical Industry.

Remarkable improvement of Ti incorporation on Hg0 capture from smelting flue gas by sulfurated γ-Fe2O3: Performance and mechanism.

Except for the dangerous Boliden-Norzink technology, recovering gaseous Hg0 as liquid Hg0 using recyclable sorbents was an achievable method to control Hg0 emissions from smelting flue gas. In this study, Ti was incorporated into sulfurated γ-Fe2O3 to improve its performance for capturing Hg0 from smelting flue gas, and the mechanism of Ti incorporation on Hg0 adsorption onto sulfurated γ-Fe2O3 was investigated by comparing the kinetic parameters. The kinetic analysis showed that the Hg0 adsorption rate primarily depended on the amounts of surface adsorption sites for the physical adsorption of Hg0 and surface S22- for Hg0 oxidation. Since the amounts of both adsorption sites and S22- on sulfurated γ-Fe2O3 increased remarkably after Ti incorporation, Hg0 adsorption onto sulfurated γ-Fe2O3 was notably improved by 190-350%. The capacity of sulfurated Fe-Ti spinel for Hg0 capture could reach 48.6 mg g-1 and its average adsorption rate could reach 43.3 µg g-1 min-1 in 3 h. Meanwhile, the used sulfurated Fe-Ti spinel could be easily regenerated without any apparent degradation. Thus, sulfurated Fe-Ti spinel offered a significant advantage in recovering Hg0 from smelting flue gas.

Removal of Hg2+ with Polypyrrole-Functionalized Fe3O4/Kaolin: Synthesis, Performance and Optimization with Response Surface Methodology.

PPy-Fe3O4/Kaolin was prepared with polypyrrole functionalized magnetic Kaolin by a simple, green, and low cost method to improve the agglomeration and low adsorption capacity of Kaolin. PPy-Fe3O4/Kaolin was employed to remove Hg2+ and the results were characterized by various methods. Relevant factors, including solution pH, dosage of adsorbent, concentration (C0), and temperature (T), were optimized by Response Surface Methodology (RSM) and Central Composite Designs (CCD). The optimal results show that the importance for adsorption factors is pH > T > C0 > dosage, and the optimal adsorption conditions of PPy-Fe3O4/Kaolin are pH = 7.2, T = 315 K, C0 = 50 mg/L, dosage of 0.05 g/L, and the capacity is 317.1 mg/g. The adsorption process conforms to the pseudo-second-order and Langmuir models. Dubinin-Radushkevich model shows that adsorption process is spontaneous and endothermic. Moreover, the adsorption of mercury by PPy-Fe3O4/Kaolin was achieved mainly through electrostatic attraction, pore diffusion, and chelation between amino functional groups and Hg2+. PPy-Fe3O4/Kaolin has excellent reproducibility, dispersity, and chemical stability, and it is easy to be separated from solution through an external magnetic field. The experiments show that PPy-Fe3O4/Kaolin is an efficient and economical adsorbent towards mercury.

Removal of Mercury (II) by EDTA-Functionalized Magnetic CoFe2O4@SiO2 Nanomaterial with Core-Shell Structure.

In order to reduce the difficulty and risk of operation, decrease the preparation time and improve the adsorption performance of magnetic nano-silicon adsorbent with core-shell structure, a carboxylated CoFe2O4@SiO2 was prepared by EDTA-functionalized method using a safe, mild and simple hydrothermal method. The results show that the prepared material of CoFe2O4@SiO2-EDTA has a maximum adsorption capacity of 103.3 mg/g for mercury ions (Hg(II)) at pH = 7. The adsorption process of Hg(II) is a chemical reaction involving chelation and single-layer adsorption, and follows the pseudo-second-order kinetic and Langmuir adsorption isotherm models. Moreover, the removal of Hg(II) is a spontaneous and exothermic reaction. The material characterization, before and after adsorption, shows that CoFe2O4@SiO2-EDTA has excellent recyclability, hydrothermal stability and fully biodegradable properties. To summarize, it is a potential adsorption material for removing heavy metals from aqueous solutions in practical applications.