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Novel phosphate-crosslinked β-cyclodextrin polymer was synthesized for highly efficient Pb(ii) removal from acidic wastewater.

Novel superhydrophilic polystyrene phosphate resin was synthesized for efficient and rapid Pb(ii) removal from acidic wastewater.

Removing heavy metal ions from acidic mine wastewater is a big challenge. In this paper, a novel porous thiophosphoryl polyethyleneimine (TPEI) adsorbent was designed for removing Pb(II) and Cr(VI) from acidic wastewater. The optimum adsorption pH value of TPEI for Pb(II) and Cr(VI) is 3 and 2, respectively. At 298 K, the maximum adsorption capacity for Pb(II) and Cr(VI) is 421.9 mg g−1 and 191.04 mg g−1, respectively. The adsorption equilibrium time of Pb(II) and Cr(VI) is 25 min and 10 min, respectively. The adsorption of Pb(II) and Cr(VI) both conform to the pseudo-second-order model and the Langmuir isotherm model. The adsorption mechanism of Pb(II) depends on the chelation interaction, while Cr(VI) depends on the electrostatic interaction. The regeneration test shows that the adsorbent is stable and reusable. This study provides a new strategy for the purification of acidic heavy metal wastewater.

To understand the possible mechanisms of hexavalent chromium (Cr(VI)) adsorption on the surface of modified layered double hydroxides (LDHs), we synthesized ethylenediaminetetraacetic acid intercalated MgAl-LDH (LDH-EDTA) and its magnetic product (Mag-LDH-EDTA), and evaluated their adsorption performance for Cr(VI) by batch equilibrium experiments. The characterization analysis proved that the EDTA was intercalated into MgAl-LDH and the adsorbents had an ordered structure and abundant functional groups. The adsorption mechanisms of Cr(VI) by LDH-EDTA and Mag-LDH-EDTA could be attributed as electrostatic attraction, surface complexation, anion exchange, and reduction reaction speculating from the detailed X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential analysis. The removal ratio remained above 96% and 79% for 50 mg L−1 Cr(VI) using 0.03 g LDH-EDTA and Mag-LDH-EDTA, respectively. The adsorption process was less influenced by the pH value of the aqueous solution. The pseudo-second-order model and the Langmuir equation well fitted to the adsorption kinetic and isotherm data. Thus, the EDTA intercalated LDH materials had potential applications for Cr(VI) removal in real wastewater treatment.

In the present study, a novel magnetic activated sludge (MAS) was successfully synthesized and applied for heavy metal removal. The MAS was characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), zeta potential analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The optimum sorption conditions were identified in view of different adsorbents, adsorbent dosages, pH values and contact times. The batch experiment implied that the pseudo-second-order model was better to describe the adsorption kinetics of Cu(II) and Cd(II) onto the MAS. The adsorption levels of Cu(II) and Cd(II) onto the MAS were in accordance with the Langmuir isotherm with maximum adsorption capacities of 72.1 and 71.3 mg g−1, respectively. According to XPS analysis, the metal sorption process was mainly caused by surface complexation, electrostatic attraction and precipitation. After four desorption cycles using Na2EDTA, the removal efficiencies of Cu(II) and Cd(II) decreased to 88.2% and 87.1%, respectively. The experimental result illustrated that the MAS could be an economical adsorbent for actual heavy metal contaminated wastewater treatment.

Though molybdenum disulfide (MoS2) has attracted widely attention in SO4•– based advanced oxidation process recently, the effect of ball milling on its catalytic efficiency is less studied. In this work, the purchased MoS2 was ball milled and applied as peroxymonosulfate (PMS) activator for degradation of tetracycline (TC). MoS2 materials with different milling time or ball-to-MoS2 mass ratio all exhibited higher degradation efficiency (77.2%–83.6%) compared with pristine MoS2 (68.1%). It was supposed that ball milling could optimize the surface properties of MoS2, especially increased the surface area and the amount of S-vacancies, thus exposed more Mo(IV) sites, which were the main active sites to react with PMS. Besides, the enhanced adsorption capacity and the accelerated generation of reactive species both benefited the catalytic efficiency of ball-milled MoS2. EPR spectra and quenching experiments showed that ball-milled MoS2 could generate more reactive species (SO4•–, •OH, O2•–, and 1O2), which favored TC degradation. The above results implied that ball-milled MoS2 materials are promising in advanced oxidation processes.

The magnetic graphene oxide and MgAl-layered double hydroxide nanocomposite (MGL) was synthesized via a simple one-pot solvothermal method, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and N2 adsorption-desorption. The results proved that the MGL nanocomposite had typical features of graphene oxide and MgAl-layered double hydroxide. Moreover, the MGL had magnetism which related to the fabrication of Fe3O4 during the solvothermal reaction, and could be easily separated from mixture with easy magnetic separation assistance. Subsequently, the MGL was used to evaluate the adsorption efficiency for lead, copper and cadmium in aqueous solutions by batch equilibrium experiments. The MGL showed excellent adsorption ability for Pb2+, Cu2+, and Cd2+. The pseudo-second-order kinetic equation and Langmuir model well fit the adsorption kinetic data and isotherm data, respectively. Furthermore, the adsorption mechanisms of Pb2+, Cu2+ and Cd2+ by MGL were detailed conducted by XRD and XPS analysis, and could be ascribed to the surface complexation, precipitation and isomorphic replacement.

The direct removal of heavy metal ions from acidic wastewater is a hard problem. In this study, a novel superabsorbent, polyvinyl alcohol phosphate ester (PVAP), was designed and prepared to remove Pb(II) from acidic wastewater (pH = 3). The PVAP can absorb water and swell to reach equilibrium within 30 s, which provides the conditions for ultrafast kinetic adsorption. For 100 mg/L Pb(II) solution, the adsorption reaches equilibrium within 5 min, and the removal ratio is more than 99.9% over a wide pH range of 3–6. Adsorption kinetics and isotherm data are consistent with pseudo-second-order and Langmuir model, respectively. The calculated maximum adsorption capacity for Pb(II) is 558.66 mg/g. Thermodynamic results show that the adsorption is spontaneous and exothermic process. The removal ratio for Pb(II) of PVAP still maintains above 99% after ten recycles. The PVAP can also simultaneously remove more than 97% of other heavy metal ions (Cu(II), Cd(II), Zn(II), Co(II), and Ni(II)) from an acidic solution. Moreover, the PVAP can efficiently purify simulated acid mine heavy metal wastewater, and the results meet EPA drinking water standards. The studies of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy prove that the adsorption mechanism involves surface complexation. This new superabsorbent is a promising candidate for acidic heavy metal sewage disposal.

Metal-free polymeric catalyst hold great promise owing to their abundant sources, low-cost fabrication and easy processibility. Melem, an important intermediate during condensation of melamine rings to graphitic carbon nitride (g-C3N4), was synthesized by simple solid phase polymerization process. A novel Melem/Zn0.25Cd0.75S composite was fabricated through a facile one-step hydrothermal method. The as-products were characterized by X-ray diffraction (XRD), UV–vis DRS spectroscopy, fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). The TEM and HRTEM results reveal that Zn0.25Cd0.75S nanoparticles and Melem closely contact with each other to form an intimate interface. The as-prepared composites exhibit significantly enhanced visible light photocatalytic performance for the degradation of Methyl orange (MO) and Bisphenol A (BPA), which could be attributed to the effective photo-induced charges transfer and separation in Melem/Zn0.25Cd0.75S composites. On the basis of radical scavenger experiments, superoxide radicals and holes are suggested to play a critical role in MO degradation over Melem/Zn0.25Cd0.75S heterojunctions. A possible mechanism for charge separation and transfer in the Melem/Zn0.25Cd0.75S composites was proposed to explain the enhanced photocatalytic performance.

The development of probes for selective detection of mercury ions (Hg2+) is an important mission to accomplish because of the toxicity and ubiquity of Hg2+. Herein, we designed and synthesized a novel fluorescent probe O-(N-butyl-1,8-naphthalimide)-4-yl-O-phenyl carbonothioate (CBONT) for selective and sensitive detection of Hg2+ by turn-on fluorescence spectroscopy. Probe CBONT exhibited a fast response for Hg2+ with excellent sensitivity (limit of detection = 1.9 nM, 3σ/slope), and it might be attributed to the adoption of a new recognition receptor of carbonothioate moiety. Additionally, probe CBONT could serve as a “naked-eye” indicator for Hg2+. Finally, probe CBONT could be successfully applied to detect the concentrations of Hg2+ in real water samples. Our proposed recognition receptor would open up new, exciting opportunities for designing highly selective and ultrasensitive fluorescent probes for the determination of Hg2+ in real water samples.

The amino-functionalized magnetite/kaolin clay (MKC) was synthesized via a simple solvothermal method and used to remove Pb2+, Cu2+, and Cd2+ from aqueous solutions. In comparison, the kaolin clay (KC) and MKC were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning and transmission electron microscopy with energy dispersive spectrometry. The results indicated amino-functionalized MKC was formed with Fe3O4 particles adhering to the surface by interactions with negatively charged KC. The optimal experimental conditions were evaluated, and the adsorption performance of MKC for Pb2+, Cu2+, and Cd2+ was far better than that of KC. This was mainly caused by adding an amino group, in which the amino group displayed complexing ability toward metal ions. In kinetic data representation, the pseudo-first-order, pseudo-second-order, and Elovich models were employed, and the second one gave the better fitting. Langmuir, Freundlich, and Dubinin–Radushkevich models were chosen for ...

We present magnetic diatomite and illite clay nanocomposites by loading Fe3O4 nanoparticles onto the raw diatomite or illite clay surfaces via a simple one-pot solvothermal method. The magnetic clays have ordered structure, rich functional groups and strong magnetism as verified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning and transmission electron microscope (SEM, TEM), and vibrating sample magnetometer (VSM). Subsequently, the magnetic diatomite (MDC) and illite clay (MIC) were used as adsorbents for fast and efficient removal of phosphate from aqueous solution by batch equilibrium experiments. The adsorption kinetic, isothermal and mechanistic properties were studied. The results demonstrated that the phosphate adsorption onto MDC and MIC was pH-dependent, completed within 30 min and possessed higher capacities than the raw clays. The adsorption kinetic and isotherm data followed the pseudo-second-order equation and the Langmuir model, respectively. The adsorption mechanisms of phosphate were ascribed to the electrostatic attraction and ligand exchange. Furthermore, the MDC and MIC endowed a superior selectivity, regeneration, reusability and can be quickly and easily separated using a magnet before and after the adsorption process.

The development of simple techniques for monitoring hypochlorous acid (HOCl) in living cells is urgently needed to disclose the important roles of HOCl in biological systems. Although a number of fluorescent probes have been exploited to detect HOCl, most of them are easily influenced by other competing reactive oxygen species (ROS) and reactive nitrogen species (RNS), and disturbed by many factors including variabilities in excitation, probe distribution and environmental conditions due to the recognition of HOCl based on the fluorescence changes in single wavelength. Herein, in this work, we present a simple fluorescent probe AETU-HOCl containing a new recognition group (2-amino-ethyl)-thiourea (AETU) for the ratiometric detection of HOCl in living cells. Probe AETU-HOCl exhibits outstanding selectivity for HOCl over other ROS/RNS at higher concentrations (0.5 mM, 100 equiv.). More importantly, the rapid response (1 min) and high sensitivity (a detection limit of 3.9 nM) allow it to successfully visualize the intracellular HOCl levels by the ratiometric imaging. The present study would offer a simple, ratiometric, rapid, and ultrasensitive assay for the accurate determination of HOCl in the biological systems.

Magnetic modified vermiculite was prepared by a simple one-pot solvothermal method to remove lead from aqueous solution. The physiochemical properties of vermiculite and magnetic vermiculite were analyzed by X-ray diffraction (XRD), surface-enhanced Raman scattering (SERS), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), specific surface area determination, and magnetic property and zeta potential measurement. The results proved that the vermiculite was successfully functionalized by nanoparticles of Fe3O4. The magnetic vermiculite had superparamagnetic property and higher specific surface areas (52.6 cm3 g−1). Batch adsorption experiments of Pb(II) by vermiculite and magnetic vermiculite were carried out. The results indicated that the adsorption isotherm and kinetic data followed the Langmuir model and the pseudo-second-order equation, respectively. The adsorption process of vermiculite and magnetic vermiculite was fast and the maximum adsorption capacities were 37.0 mg g−1 and 70.4 mg g−1, respectively. In addition, the magnetic vermiculite can be fleetly and easily separated using a magnet after adsorption. It has good potential for cost-effective treatment of lead-contaminated wastewater.

EDTA functionalized magnetic graphene oxide (EDTA-mGO), a good adsorbent for Pb(II), Hg(II) and Cu(II), was synthesized in the present work. It was characterized by SEM, FTIR, BET, XRD, XPS, TGA and zeta potential analysis. Contact time, adsorbent dose, pH and initial concentration were optimized to improve the removal efficiency. Most importantly, EDTA-mGO displayed better adsorption performance than EDTA-GO, EDTA-Fe3O4 and mGO. The adsorption of Pb(II), Hg(II) and Cu(II) mainly depend on the metal chelation of EDTA and the electrostatic attractions of abundant functional groups on GO surface. Besides, good magnetic performance of EDTA-mGO makes it easy to achieve the solid–liquid separation. The magnetic separation process only took 25 s. The adsorption kinetic data described well with the pseudo-second-order model and the equilibrium data fitted well to Freundlich and Temkin isotherms. The maximum adsorption capacity was 508.4 mg g−1 for Pb(II), 268.4 mg g−1 for Hg(II) and 301.2 mg g−1 for Cu(II) from Langmuir isotherm. Thermodynamic studies (ΔG 0, ΔS > 0) implied an endothermic and spontaneous adsorption process in nature. Furthermore, the excellent reproducibility indicated that EDTA-mGO has a promising application in water treatment.

To reuse the spent magnetic MgAl-layered double hydroxide after humic acid adsorption, this work provided a simple calcination method to prepare the magnetic layered double oxide/carbon (Mag-LDO/C) nanocomposite. The characterization results indicated the Mag-LDO/C was a carbonaceous composite with a large number of functional groups and superparamagnetic property. Then the adsorption performance of Mag-LDO/C for heavy metals was studied by batch experiments. The Mag-LDO/C exhibited excellent removal efficiencies for Cd(II), Pb(II), and Cu(II) with maximum adsorption capacities of 386.1, 359.7, and 192.7 mg/g, respectively. The batch sorption data were studied by the pseudo-second-order kinetic equation and the Langmuir isothermal model, and they matched well. According to the zeta potentials, X-ray diffraction patterns, and X-ray photoelectron spectra of Mag-LDO/C after heavy metals adsorption, the interaction mechanisms were ascribed to the precipitation, surface complexation, and electrostatic attraction. After reaction, the solid-liquid separation of Mag-LDO/C could quickly achieve using a magnet. Additionally, the Mag-LDH/C exhibited excellent adsorption capacities in various simulated wastewater and well sorption recyclability, proving the valuable applications of Mag-LDO/C synthesized from spent adsorbent for metal ions removal in actual water environment.

Mercury (Hg) and its derivatives pose a serious threat to the environment and human health because of their durability, easy transference, and high biological accumulation. Thus, the development of methods for selective and sensitive determination of Hg2+ is very important to understand its distribution and implement more detailed toxicological studies. Herein, we report a simple 4-hydroxynaphthalimide-derived fluorescent probe (1) for the detection of both inorganic and organic mercury species in aqueous solution. Probe 1 could quantificationally detect mercury species by fluorescence spectroscopy with high selectivity and sensitivity. Importantly, probe 1 could serve as a “naked-eye” indicator for mercury species and exhibited a large fluorescent enhancement with the help of hydrogen peroxide (H2O2). Additionally, the mechanism of the reaction between probe 1 and mercury species was confirmed using 1H NMR and ESI-MS. And, analytical applications of probe 1 to the river water samples further demonstrated...

Platinum–lead (PtPb) hollow nanoparticles were used as signal tags for the first time to fabricate an electrochemical immunosensor, which was then used as the first electrochemical immunosensor to detect dimethyl phthalate (DMP). Pt nanoparticles possess good biocompatibility, highly efficient catalytic properties and good electrical conductivity. Pb was introduced to produce electrochemical signals, reduce the dosage of the noble metal and save costs. An AuPt–graphene sheet (AuPt–GS) was used to immobilize the DMP antibodies (Anti-DMP) due to its excellent conductivity and large surface area. A novel competitive immunoassay was proposed, using PtPb nanoparticles covalently conjugated with bovine serum albumin (BSA)–DMP for the sensitive detection of DMP concentrations. The quantitative detection was based on the competitive binding of DMP antibodies with PtPb-tagged DMP or free DMP. The electrochemical signal decreased with increasing concentration of the free DMP as the amount of PtPb–BSA–DMP tags decreased at the immunosensor. Electron microscopy, energy dispersive spectrometry, X-ray powder diffraction and a series of electrochemical techniques were used to characterize the nanoparticles. Differential pulse voltammetry was used to monitor the electrochemical response. The immunosensor exhibited a linear response from 1 to 1000 ng mL−1 DMP with a detection limit of 0.33 ng mL−1. The excellent performance of the PtPb nanoparticles showed promising applications as a sensor platform.

In this paper, carboxymethyl functionalized chitosan was used for the synthesis of a magnetic polysaccharide–graphene oxide composite (SCGO). Compared with the magnetic chitosan–graphene oxide composite reported before, adsorption capacity in this research had improved significantly. The calculated maximum adsorption capacity values for methylene blue (MB) and malachite green (MG) were 358.4 mg g−1 and 289.1 mg g−1, respectively. The morphology, chemical properties and physical structure of SCGO were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The influence factors which included pH, adsorbent dose, ionic strength and contact time on the adsorption properties of MB and MG onto SCGO were investigated. The adsorption kinetics of MB and MG on SCGO were well-described by pseudo-second order kinetic models. The experimental data of the isotherm followed the Temkin isotherm model and the Langmuir model, respectively. Thermodynamic analysis was also performed to calculate the changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS). The results obtained from this research suggested that SCGO was a potential adsorbent for effective removal of methylene blue and malachite green.

Calcined ZnAl- and Fe3O4/ZnAl–layered double hydroxides (ZnAl–CLDH and Fe3O4/ZnAl–CLDH) were used as adsorbents to evaluate the uptake properties for Cr(VI) removal from aqueous solution by batch equilibrium experiments. The XRD, FTIR and TEM results showed that the calcined ZnAl–LDH and Fe3O4/ZnAl–LDH recovered layered structures according to the memory effect of hydrotalcite. Optimized conditions of Cr(VI) adsorption were obtained: 2.0 g L−1 adsorbent, initial solution pH of 3.0 and contact time of 60 min. The kinetic data was described better by a pseudo-second-order kinetic equation. The adsorption isotherms had a good fit with Langmuir and Freundlich models. Thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous in nature. The adsorption mechanisms involved the reconstruction of LDHs, surface complexation, anion exchange and physical adsorption. The higher adsorption capacities of the calcined products suggested that the ZnAl–CLDH and Fe3O4/ZnAl–CLDH were potential adsorbents for Cr(VI) removal from water and wastewater. Moreover, the magnetic Fe3O4/ZnAl–CLDH can be easily separated using a magnet after the adsorption process.

Herein, coralloid Cu2S nanoparticles were prepared through a facile etching method and used as labels for the first time to fabricate an electrochemical immunosensor. A novel competitive immunoassay was then proposed using Cu2S covalent conjugation with bovine serum albumin (BSA)–estradiol (E2) for the sensitive detection of trace E2 concentrations. Without using enzyme-label and acid dissolution, the Cu2S can generate excellent electrochemical signals. The quantitative detection was based on the competitive binding of the E2 antibody with Cu2S-labeled E2 or free E2. The redox signal decreased with increasing concentration of the free E2 as the amount of Cu2S–BSA–E2 labels decreased at the immunosensor probe. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to characterize the immunosensor. Square wave voltammetry was used to monitor the electrochemical response. The immunosensor exhibited a wide linear response from 25 to 7500 pg mL−1 with a detection limit of 7.5 pg mL−1. The proposed method showed good precision, broad linear range, and acceptable stability and could be used for the detection of E2 in real samples, which showed promising application in field research.

Magnetic material as adsorbent can provide effective remove and quickly separate of pollutant in wastewater treatment. A magnetic Fe 3 O 4 /MgAl-layered double hydroxide (LDH) composite was prepared by low saturation coprecipitation in the dispersed Fe 3 O 4 suspension. The characterization of XRD, TEM and FTIR revealed that the Fe 3 O 4 /MgAl-LDH composite was combined with Fe 3 O 4 and MgAl-LDH. This provided the composite of magnetic property which improved the separation of solid from aqueous solution. The adsorption of reactive red (RR), congo red (CR) and acid red 1 (AR1) by magnetic Fe 3 O 4 /MgAl-LDH composite depended upon the adsorbent dosage, contact time, initial concentration and temperature. The adsorption of the three red dyes reached equilibrium at 30 min and followed the pseudo-second-order kinetic equation. The equilibrium adsorption isotherm data well fitted the Langmuir model for RR, Freundlich model for CR and AR1. Thermodynamic results demonstrated that the adsorption processes were spontaneous, endothermic for RR and CR or exothermic for AR1. The adsorption capacities changed insignificantly between solution pH 2–10 and the maximum were 97, 253 and 92 mg/g for RR, CR and AR1, respectively. Moreover, the solid composite can be quickly separated from the aqueous solution by an external magnet before and after adsorption process. This indicated that the magnetic Fe 3 O 4 /MgAl-LDH composite was an effective adsorbent for red dyes removal with quick separation.

Currently, growing attention has been paid to the sensitive determination and removal of Cu2+ because excessive levels of Cu2+ could do harm to organisms. Herein, a novel diethanolamine-modified magnetic fluorescent Fe3O4@ZnS nanoparticle (MFNP) for simultaneous detection and removal of Cu2+ was designed and synthesized through dithiocarbamate linkage strategy. The characterization of MFNP was confirmed by transmission electron microscope (TEM), infrared (IR) and emission spectra. The results showed that MFNP could quantificationally detect Cu2+ with high sensitivity and selectivity under a broad pH range (pH 4.5-9). The removal of Cu2+ was achieved by the aggregation-induced sedimentation (AIS) strategy and by external magnetic field.

The objective of this study was to evaluate the conversion of full nitritation to partial nitrification processes by altering the influent ammonium concentration in a sequencing batch reactor at ambient temperature. After 150 days’ operation, full nitritation and partial nitrification processes were successfully achieved when the influent NH 4 + – N concentrations up to 400 and 720 mg/L, respectively. Meanwhile, sludge volumetric index (SVI) gradually decreased from 127.4 to 63.4 mL/g, while the average size of sludge improved from 29.5 to 195.6 μm by the strategy of reducing settling time. Ammonium-oxidizing bacteria (AOB) were the dominant nitrifying bacteria according to the fluorescence in situ hybridization (FISH) analysis. Free ammonia (FA) and free nitrous acid (FNA) were the potential compounds for inhibiting the activity of nitrite-oxidizing bacteria (NOB). The obtained results may help to promote the development of new biological nitrogen removal processes in engineering, especially in relation to nitrogen-rich wastewaters.

A facile and template free in situ precipitation method was developed for the synthesis of a g-C3N4/Zn0.25Cd0.75S photocatalyst. The obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible diffuse reflection spectroscopy (DRS). The DRS results showed that with the increase of the g-C3N4 content, the light absorption edge for g-C3N4/Zn0.25Cd0.75S was blue shifted in the visible light region. The TEM images showed that the Zn0.25Cd0.75S particles had been finely distributed on the surfaces of the g-C3N4 sheets. The HRTEM images showing clear lattice fringes proved the formation of a heterojunction structure at the interfaces of g-C3N4 and Zn0.25Cd0.75S. In the photocatalytic degradation of dyes, the g-C3N4/Zn0.25Cd0.75S composite exhibited significantly enhanced activities, and the optimal g-C3N4 content was 20 wt%. A controlled experiment showed that the high charge separation efficiency of the photo-generated electron–hole pairs and the suitable energy band structures result in the high performance of g-C3N4/Zn0.25Cd0.75S under visible light irradiation. The g-C3N4/Zn0.25Cd0.75S sample also possessed a superior activity in the photocatalytic reduction of Cr(VI) in neutral solution. The photoelectrochemical measurements confirmed that the interface charge separation efficiency was greatly improved by coupling g-C3N4 with Zn0.25Cd0.75S. A terephthalic acid photoluminescence probing technique has been performed to detect the generation of ˙OH in the reaction system.

In this paper, amino functionalized graphenes (NH2-G) were synthesized for the efficient removal of an acid dye, Metanil Yellow (MY). The morphology, physical structure and chemical properties of the NH2-G were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and N2 adsorption–desorption isotherms, respectively. Batch experiments were conducted on the adsorption of MY by the prepared modified graphenes to investigate the effect of several parameters such as pH, dye concentration, adsorption time and temperature. Optimal conditions for the adsorption system were as follows: pH of 7, 0.4 g L−1 adsorbent and contact time of 120 min with the maximum adsorption capacity of 71.62 mg g−1. The adsorption mechanism was investigated by (on the basis of) adsorption isotherms, adsorption kinetic and adsorption thermodynamics. MY adsorption by NH2-G was better fitted by both Langmuir isotherm among five different equilibrium models and pseudo-second-order kinetic model. Furthermore, the thermodynamic experiments results with the values of activation parameters such as free energy (ΔG, −4.729 to −5.592 kJ mol−1), enthalpy (ΔH, 8.120 kJ mol−1) and entropy (ΔS, 43.08 J mol−1 K−1) illustrated that the adsorption process of MY onto NH2-G was endothermic and spontaneous in nature. The results obtained in this study suggest that NH2-G is an excellent adsorbent for effective removal of Metanil Yellow from water.

A novel 1,8-naphthalimide-functionalized Fe 3 O 4 @SiO 2 core/shell magnetic fluorescent nanoparticles ( MFNPs ) for simultaneous detection and adsorption of Hg 2+ was designed and synthesized. A series of adsorption studies were carried out with various Hg 2+ concentrations, temperature, time and pH. The maximum adsorption capacity is higher than 30 mg/g over a broad temperature (0 °C, 25 °C, and 50 °C) and pH (4–10). The results showed that MFNPs possesses an excellent reusability and the high adsorption specificity toward Hg 2+ . The detection limit for Hg 2+ is 3.4 nM. In addition, owing to the aggregation of MFNPs occurring in the Hg 2+ aqueous solution, the adsorbent was separated easily by the settlement or the external magnetic field, which facilitated the removal of Hg 2+ .

© 2015 Elsevier B.V. Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g-1 for Pb(II) and 740.7 mg g-1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (ΔG0, ΔS>0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and electrostatic attraction dominated the adsorption of Pb(II) and π-π stacking interactions and electrostatic attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.

Amine-functionalized mesoporous Fe3O4 nanoparticles (AF-Fe3O4) were developed for the highly efficient removal of toxic heavy metal ions from water. AF-Fe3O4 were prepared by a new cost-effective and environmentally friendly procedure. The maximum amino-group grafted onto AF-Fe3O4 is 0.1790 μg/mg by ninhydrin test. AF-Fe3O4 can be simply recovered from water with magnetic separations at low magnetic field within 1 min. Each adsorption of 50 mL 5 mg/L of Pb(II), Cd(II), and Cu(II) onto 10 mg of AF-Fe3O4 reached equilibrium within 120 min at pH 7.0. It agreed well to the Langmuir adsorption model with maximum adsorption capacities for Pb(II), Cd(II), and Cu(II) from 369.0 to 523.6 mg/g, which is larger than some other reports. The adsorption rates of Pb(II), Cd(II), and Cu(II) on AF-Fe3O4 fit pseudo-second order kinetic models (R2 > 0.99). Thermodynamic studies illustrated the adsorption process was endothermic and spontaneous. AF-Fe3O4 was able to remove over 98% of Cu(II), Cd(II) and Pb(II) in 50 mL of solution containing 5 mg/L metal ions at optimized conditions.

Field experiments were conducted to explore the effects of different sewage sludge amendment strategies on the accumulation and translocation of polybrominated diphenyl ethers (PBDEs) in soil-wheat systems. Two types of application methods (single or annual application) and four annual application rates (5, 10, 20, and 40 t ha(-1) year(-1)) were investigated. BDE 209 was detected in all of the sewage sludge amended soils and different parts of wheat plants collected from the contaminated soils. However, the other seven PBDE congeners (BDE 28, BDE 47, BDE 99, BDE 100, BDE 153, BDE 154, and BDE 183) were not detected or were only observed at very low levels. A single application of sewage sludge in large quantities would likely increase accumulation of BDE 209 in soil and its subsequent uptake and translocation by wheat. The concentrations of BDE 209 in soils, wheat roots and straws increased with the increasing sewage sludge application rate. There is a negative correlation between the root accumulation factors (the ratios of concentrations in wheat roots to those in soils) and soil total organic carbon (R(2)=0.84,P0.05), demonstrating that the bioavailability of BDE 209 was controlled by the soil total organic carbon. BDE 209 concentrations in the grains from the sewage sludge amended soils were not significantly different from those of the control soils, suggesting that atmospheric deposition was the main source of BDE 209 detected in the grains.

Recently, much attention has been paid to the selective detection and removal of Cu2+ because an excess of Cu2+ can harm the environment and living systems. Herein, we developed a novel water-soluble di-2-picolylamine/proline co-modified Fe3O4@ZnS magnetic fluorescent nanoparticle (MFNP-Cu) for the selective detection and removal of Cu2+ through a dithiocarbamate linkage strategy. The characterization of MFNP-Cu was confirmed by x-ray diffraction (XRD), transmission electron microscope (TEM), magnetization hysteresis loops, infrared (IR) and emission spectra. The results showed that MFNP-Cu could quantifiably detect Cu2+ with high sensitivity and selectivity over a broad pH range (pH 4.1-9). The maximum adsorption capacity of MFNP-Cu was calculated to be about 517.9 mg g(-1), which is higher than previously reported. This excellent property was investigated by kinetics equilibrium and thermodynamic studies. Moreover, the removal properties of MFNP-Cu toward Cu2+ from contaminated water samples was achieved by an external magnetic field.