Integrated Circuit of a Chua's System Based on the Integral-Differential Nonlinear Resistance with Multi-Path Voltage-Controlled Oscillator.

In this paper, we present a fully integrated circuit without inductance implementing Chua's chaotic system. The circuit described in this study utilizes the SMIC 180 nm CMOS process and incorporates a multi-path voltage-controlled oscillator (VCO). The integral-differential nonlinear resistance is utilized as a variable impedance component in the circuit, constructed using discrete devices from a microelectronics standpoint. Meanwhile, the utilization of a multi-path voltage-controlled oscillator ensures the provision of an adequate oscillation frequency and a stable waveform for the chaotic circuit. The analysis focuses on the intricate and dynamic behaviors exhibited by the chaotic microelectronic circuit. The experimental findings indicate that the oscillation frequency of the VCO can be adjusted within a range of 198 MHz to 320 MHz by manipulating the applied voltage from 0 V to 1.8 V. The circuit operates within a 1.8 V environment, and exhibits power consumption, gain-bandwidth product (GBW), area, and Lyapunov exponent values of 1.0782 mW, 4.43 GHz, 0.0165 mm2, and 0.6435∼1.0012, respectively. The aforementioned circuit design demonstrates the ability to generate chaotic behavior while also possessing the benefits of low power consumption, high frequency, and a compact size.

Reduction and adsorption of uranium(VI) from aqueous solutions using nanoscale zero-valent manganese.

Nano zero-valent manganese (nZVMn) is theoretically expected to exhibit high reducibility and adsorption capacity, yet its feasibility, performance, and mechanism for reducing and adsorbing hexavalent uranium (U(VI)) from wastewater remain unclear. In this study, nZVMn was prepared via borohydride reduction, and its behaviors about reduction and adsorption of U(VI), as well as the underlying mechanism, were investigated. Results indicated that nZVMn exhibited a maximum U(VI) adsorption capacity of 625.3 mg/g at a pH of 6 and an adsorbent dosage of 1 g/L, and the co-existing ions (K+, Na+, Mg2+, Cd2+, Pb2+, Tl+, Cl-) at studied range had little interference on U(VI) adsorption. Furthermore, nZVMn effectively removed U(VI) from rare-earth ore leachate at a dosage of 1.5 g/L, resulting in a U(VI) concentration of lower than 0.017 mg/L in the effluent. Comparative tests demonstrated the superiority of nZVMn over other manganese oxides (Mn2O3 and Mn3O4). Characterization analyses, including X-ray diffraction and depth profiling X-ray photoelectron spectroscopy, combined with density functional theory calculation revealed that the reaction mechanism of U(VI) using nZVMn involved reduction, surface complexation, hydrolysis precipitation, and electrostatic attraction. This study provides a new alternative for efficient removal of U(VI) from wastewater and improves the understanding of the interaction between nZVMn and U(VI).

Corn stalk pith-based hydrophobic aerogel for efficient oil sorption.

Bio-based aerogel has become an attractive sorbent for spilled oil and organic pollutants because of its light weight, high porosity and strong sorption capacity. However, the current fabrication process is mainly "bottom-up" technology, which is cost-expensive, time-consuming, and energy-intensive. Herein, we report a top-down, green, efficient and selective sorbent prepared from corn stalk pith (CSP) using the deep eutectic solvent (DES) treatment, followed by TEMPO/NaClO/NaClO2 oxidization and microfibrillation, and then hexamethyldisilazane coating. Such chemical treatments selectively removed lignin and hemicellulose, broke the thin cell walls of natural CSP, forming an aligned porous structure with capillary channels. The resultant aerogels had a density of 29.3 mg/g, a porosity of 98.13%, and a water contact angle of 130.5◦, exhibiting excellent oil/organic solvents sorption performance, with a high sorption capacity in the range of 25.4-36.5 g/g, approximately 5-16-fold higher than CSP, and with fast absorption speed and good reusability.

Thallium removal from wastewater using sulfidized zero-valent manganese: Effects of sulfidation method and liquid nitrogen pretreatment.

Zero-valent manganese (ZVMn) possesses high reducibility in theory, while sulfide exhibits strong affinity towards a variety of heavy metals owing to the low solubility of metal sulfides. Yet the performance and mechanisms on using sulfidized zero-valent manganese (SZVMn) to remove thallium (Tl) from wastewater still remain unclear. In this study, the performance of Tl(I) removal using SZVMn synthesized by borohydrides reduction followed by sulfides modification, with and without liquid nitrogen treatment, was compared and the mechanism behind was investigated. The results show that at a S/Mn molar ratio of 1.0, liquid nitrogen modified SZVMn (LSZVMn) possessed more interior channels and pores than SZVMn, with 65.3% higher specific surface area and 73.7% higher porosity, leading to 6.4-8.1% improvement in adsorption of Tl(I) at pH 4-10. LSZVMn showed effectiveness and robustness in Tl(I) removal in the presence of co-existing ions up to 0.1 M. The adsorption of Tl(I) conformed to the pseudo-1st-order kinetic model, and followed the Langmuir isothermal model, with the maximum Tl adsorption capacity of 264.9 mg·g-1 at 288 K. The mechanism of Tl(I) removal with SZVMn was found to include sulfidation-induced precipitation, manganese reduction, surface complexation, and electrostatic attraction. The liquid nitrogen pretreatment embrittled and cracked the outer shell of S/Mn compounds, resulted in a highly hierarchical structure, enhancing the manganese reduction and improving the Tl(I) removal. Based on the above results, the SZVMn and its liquid nitrogen-modified derivatives are novel and effective environmental materials for Tl(I) removal from wastewater, and the application of SZVMn to the removal of other pollutants merits investigation in future study.

Efficient removal of antimonate and antimonite by a novel lanthanum-manganese binary oxide: Performance and mechanism.

Antimony is a highly toxic pollutant and its removal from water gains increasing attention. To effectively remove both Sb(III) and Sb(V), a novel lanthanum-manganese binary oxide (L1M2BO) adsorbent was synthesized by a simple oxidation coupled with precipitation method. The as-prepared L1M2BO was detailedly characterized by the XRD, SEM, TEM, BET, FTIR and XPS techniques. It is amorphous and irregular in shape, with a particle size of 50-100 nm and a specific surface area of 180.4 m2/g. A remarkable synergistic effect between the lanthanum hydroxide and Mn oxide in improving antimony adsorption is shown. The maximum adsorption capacities of Sb(III) and Sb(V) are 364.6 mg/g and 131.1 mg/g at pH 7.0, respectively, which outcompete most of reported adsorbents. The adsorption behaviors of antimony fitted well the pseudo-second-order kinetic and Freundlich models. The adsorption mechanism of Sb(V) involves mainly the replacement of surface metal hydroxyl and forming inner-sphere complex. While the Sb(III) removal is a more complicated process, containing both Sb(III) adsorption and oxidation to Sb(V). Furthermore, the spent L1M2BO sorbent can be regenerated and reused. The L1M2BO could be used as an attractive adsorbent for antimony removal, owing to its easily fabrication, high effectiveness and reusability.

Oil/water separation using elastic bio-aerogels derived from bagasse: Role of fabrication steps.

Bio-aerogels hold great promise for selective oil separation from water due to their light weight and high sustainability. However, how the fabrication methods impact the elasticity and oil sorption performance of bio-aerogels still needs systematic comparison and in-depth investigation. In this study, the fabrication of hydrophobic bio-aerogels with good elasticity and reusability was optimized using a factorial design based on the dosages of bagasse-derived cellulose nanofiber, sodium alginate, and calcium carbonate. The role of each key fabrication step, including ice-templating, calcium crosslinking, solvent dehydration, freeze-drying, and silanization, played in the material properties was also elucidated. The optimized bio-aerogels had a low density (7.55 mg/cm3), high porosity (99.47%), large specific surface area (39 m2/g), and strong hydrophobicity (water contact angle of 135°). In addition, the bio-aerogels exhibited outstanding selective oil separation ability towards the oil-water mixture, with oil sorption capacity of 89-126 times its weight. The in-situ calcium crosslinking and solvent dehydration were vital to create porosity and preserve the microstructure of the bio-aerogels. The chemical vapor deposition rendered the bio-aerogels hydrophobic and oleophilic, greatly enhancing the separability of oil from the water-oil mixture.

Potential application of Fusarium fungal strains (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) for removal of Tl (I) ions from water.

Water pollution caused by heavy metals poses a serious threat to the ecosystem and human health. Among the various treatment techniques for water remediation, adsorption is an efficient method due to its high capacity, low cost, and simplicity. Thallium (Tl) is highly toxic to mammals and its removal from water is gaining increasingly prominent attention. In this study, three fungal strains (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) were tested for removal of Tl (I) from aqueous solutions and showed excellent removal performance. The prepared inactive fungal strains were characterized by XRD, FT-IR, SEM, and XPS analyses. The effects of pH, contact time, biomass dosage, and reaction temperature on the removal efficiency of Tl (I) were systematically investigated. The results indicated that the adsorption isotherm data fit well with the Langmuir model, and the pseudo-second-order model was more consistent with the kinetic data description. The maximum adsorption capacity of the fungal strain (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) for Tl (I) was found to be 94.69 mg/g, 66.97 mg/g, and 52.98 mg/g, respectively. The thermodynamic data showed that the sorption process was spontaneous and endothermic. The present study showed that the inactive fungal strains could be a promising adsorbent material for Tl (I) removal.

Highly efficient removal of thallium(I) by facilely fabricated amorphous titanium dioxide from water and wastewater.

In this study, amorphous hydrous titanium dioxide was synthesized by a facile precipitation method at room temperature, aiming to effectively remove thallium(I) from water. The titanium dioxide prepared using ammonia as precipitant (TiO2I) is more effective for thallium(I) uptake than the one synthesized with sodium hydroxide (TiO2II). The TiO2 obtained particles are amorphous, aggregates of many nanoparticles and irregular in shape. The thallium(I) uptake increases with the rise of solution pH value. Under neutral pH conditions, the maximal thallium(I) adsorption capacities of TiO2I and TiO2II are 302.6 and 230.3 mg/g, respectively, outperforming most of the reported adsorbents. The amorphous TiO2 has high selectivity towards thallium(I) in the presence of multiple cations such as K+, Ca2+, Mg2+, Zn2+ and Ni2+. Moreover, the TiO2I is efficient in removing thallium(I) from real river water and mining wastewater. Additionally, the spent TiO2I can be regenerated using hydrochloric acid solution and reused. The Tl(I) adsorption is achieved via replacing the H+ in hydroxyl group on the surface of TiO2 and forming inner-sphere surface complexes. Owing to its high efficiency, facile synthesis and environmental friendliness, the TiO2I has the potential to be used as an alternative adsorbent to remove Tl(I) from water.

Multi-step purification of electrolytic manganese residue leachate using hydroxide sedimentation, struvite precipitation, chlorination and coagulation: Advanced removal of manganese, ammonium, and phosphate.

Water pollution caused by the release of manganese (Mn2+) and ammonia nitrogen (NH4+-N) from electrolytic manganese residue (EMR) generated from industrial activities poses a serious threat to ecosystems and human health. In this study, an integrated process consisting sequentially of hydroxide sedimentation, struvite precipitation, breakpoint chlorination, and ferric chloride coagulation was optimized to remove Mn2+ and NH4+-N from EMR leachate, and to address the issue of residual orthophosphate caused by struvite precipitation. The precipitates were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analyses. Results show that Mn2+ ions and the resulting chemical oxygen demand (COD) were mainly removed using hydroxide precipitation at a sedimentation pH of 10.2, with poor-crystalline manganese hydroxide as the main precipitate. NH4+-N was primarily removed and recovered using struvite precipitation with well crystalline struvite as the main product, and then further eliminated using breakpoint chlorination. The residual orthophosphate introduced by struvite precipitation is successfully removed with ferric coagulation, and the effluent pH (7.5) is also lowered to discharge limits by means of hydrolysis of ferric coagulant. The concentration of COD, Mn2+, NH4+-N, and orthophosphate concentrations in the final effluent were 30.52 ± 9.38, 0.026 ± 0.013, 0.87 ± 0.01, and 0.06 ± 0.002 mg/L, respectively, meeting all local discharge standards. This combined process has robust pollutant removal efficiency, high resource recovery potential and few environmental constraints; thus, it is recommended as a potential solution for the treatment of Mn2+- and NH4+-N-rich acid mine drainage.

Effective multi-functional biosorbent derived from corn stalk pith for dyes and oils removal.

In this study, malic acid-modified corn stalk pith (MA-CSP) was prepared as an environmentally friendly multi-functional bio-sorbent for adsorbing of dyes and oils. The sorption capacity of the MA-CSP for single and binary dyes is 328.46 mg/g - 566.27 mg/g. In addition, the MA-CSP also had good sorption for lubricating oil, soybean oil, diesel oil, and isopropyl alcohol, which were 37.2 g/g, 44.1 g/g, 33.8 g/g, and 29.3 g/g, respectively. Physical and statistical models were used to analyze the adsorption behavior of methylene blue (MB) and crystal violet (CV). And its sorption behavior for dyes was also affected by the co-existing salts in water. The sorption mechanism of the dye was mainly electrostatic attraction and hydrogen bonding action. The sorption of oil was primarily via the role of van der Waals force and hydrophobic interaction. The MA-CSP, as an eco-friendly, economical and efficient multi-functional sorbent, holds promise for effective dyes and oil removal from contaminated water, and its application in other fields is also highly anticipated.

Biosorbent with superhydrophobicity and superoleophilicity for spilled oil removal.

The development of efficient and sustainable sorbents for emergent oil cleanup has attracted tremendous attention. In this study, the feasibility of enzymatic grafting of octadecylamine (ODA) on corn stalk pith (CSP) by laccase-TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) treatment for enhanced oil-water separation was investigated. The dynamic contact angle tests suggest that the modified CSP (LCSP) had higher hydrophobicity (WCA, 157.2˚) and lipophilicity (OCA, 0˚) than the CSP did. In addition, the introduction of ODA onto the surface of modified CSP was verified by a variety of characterization techniques including SEM, FT-IR, and XPS. Compared with the control, laccase-TEMPO treatment of CSP coupled with octadecylamine grafting greatly improved the oil sorption capacity from 13.24 g/g to 44.25 g/g, while substantially reduced the water sorption capacity from 15.52 g/g to 2.76 g/g. LCSP has fast kinetic (sorption equilibrium reached before 60 min) and high fits to the pseudo-second-order kinetic model. The results obtained in this study reveal the feasibility of using Laccase-TEMPO treatment to graft the ODA onto the surface of CSP, thereby enhancing the rate and capacity of oil separation from oily water. The method and sorbent developed in this study hold promise for green, simple and cost-effective oil cleanup during oil spillage emergency events.

Highly efficient removal of thallium(I) from wastewater via hypochlorite catalytic oxidation coupled with adsorption by hydrochar coated nickel ferrite composite.

In this study, tannery wastewater was used as carbon source to hydrothermally synthesize magnetic carbon-coated nickel ferrite composite (NiFe2O4@C), which was employed as a catalyst for thallium (Tl) oxidation by hypochlorite and simultaneously as an adsorbent for Tl removal from wastewater. Compared with NiFe2O4@C adsorption or hypochlorite oxidation alone, the combination of NiFe2O4@C and hypochlorite substantially enhanced the rate and efficiency of Tl(I) removal. In addition, this process was highly effective for Tl(I) removal over a wide pH range (6-12). The maximum Tl(I) removal capacity was 1699 mg/g at pH 10, which is the highest one reported so far. Electron spin resonance spectra suggested the formation of hypochlorite-based free radicals induced by the NiFe2O4@C composite, which enhanced the Tl(I) oxidation and removal. Oxidation-induced surface precipitation and surface complexation were found to be the main Tl(I) removal mechanisms. Consecutive cyclic regeneration tests implied robust regeneration and reuse performance of the composite. Moreover, it was effective for Tl(I) removal from real industrial wastewater. Therefore, the hypochlorite catalytic oxidation coupled with adsorption by the magnetic NiFe2O4@C composite is a promising technique for Tl(I) removal from wastewater. This hybrid process also has great potential for the removal of other pollutants.

Zero-valent iron-manganese bimetallic nanocomposites catalyze hypochlorite for enhanced thallium(I) oxidation and removal from wastewater: Materials characterization, process optimization and removal mechanisms.

Nano zero-valent metals adsorption coupled with advanced oxidation for environmental pollutants removal has been gaining attention recently. In this study, zero-valent iron-manganese (nZVIM) bimetallic nanocomposites were prepared via one-pot borohydride reduction and coupled with hypochlorite (ClO-) oxidation for enhanced thallium (Tl) removal from wastewater. Amorphous nZVIM nanoparticles were successfully synthesized, with a specific surface area of 106.89 m2/g, and a saturation magnetization of 65.16 emu/g. In comparison with the nZVIM adsorption or ClO- oxidation alone, the hybrid nZVIM/ClO- process achieved much faster Tl(I) removal rate over a wide pH range from 6 to 10. Maximum Tl(I) removal capacity was as high as 990.0 mg/g. The oxidation-induced adsorption for Tl(I) removal well followed the pseudo-first kinetic order model. Stable and effective adsorbent regeneration was achieved during the cyclic adsorption-desorption tests. This process also had high resistance to the interference of external cations, can act as an effective pretreatment for Tl(I) removal from the actual saline industrial wastewater. The main mechanisms for Tl(I) removal were found to be oxidation, surface precipitation, pore retention, and surface complexation. The nZVIM coupled with ClO- approach has great potential for Tl(I) removal from wastewater, and its application in other fields is highly anticipated.

Carbon quantum dots derived from the extracellular polymeric substance of anaerobic ammonium oxidation granular sludge for detection of trace Mn(vii) and Cr(vi).

Carbon quantum dots (CQDs) were synthesized via a hydrothermal method, in which extracellular polymeric substance (EPS) from anaerobic ammonium oxidation (anammox) granular sludge was used as a carbon precursor, while citric acid and ethylenediamine were applied as auxiliary carbon source and passivation agent, respectively. The synthesized CQDs, with orderly spherical shape and mean size of 7.15 nm, emitted blue fluorescent light under UV radiation of 365 nm. The CQDs had a high fluorescence yield (40.84%), with good water solubility and excellent spectroscopic properties. In addition, the CQDs exhibited selective, sensitive and distinctive fluorescence quenching behaviors for Cr(vi) and Mn(vii) in a PBS buffer solution (NaH2PO4-Na2HPO4) of pH 7, with a detection limit of 5.8 nM for Cr(vi) and 2.3 nM for Mn(vii). Owing to the nitrogen components from the EPS of anammox granules, the CQDs were well nitrogen-doped, promoting electron-transfer and leading to reduction between the CQDs and Mn(vii)/Cr(vi). These results indicate that CQD-based chemical sensing is a simple and efficient means for the fluorescence detection of Mn(vii) and Cr(vi).

Enhanced thallium(I) removal from wastewater using hypochlorite oxidation coupled with magnetite-based biochar adsorption.

The development of efficient and regenerable adsorbent coupled with advanced oxidation for enhanced thallium (Tl) removal has been a recent focus on wastewater treatment. In this study, a magnetite-based biochar derived from watermelon rinds was synthesized and used as a sustainable adsorbent and catalyst for hypochlorite oxidation and removal of Tl(I) from wastewater. The addition of hypochlorite substantially enhanced the Tl(I) removal under normal pH range (6-9). Maximum Tl adsorption capacity of 1123 mg/g was achieved, which is 12.3% higher than the highest value previously reported. The magnetic biochar can be regenerated using 0.1 mol/L HNO3 solution for elution in only 5 min, with a Tl desorption efficiency of 78.9%. The Tl removal efficiency was constantly higher than 98.5% during five consecutive recycle tests, indicating the effective reuse performance of the adsorbent. Oxidation, surface precipitation, pore retention and surface complexation were the main mechanisms for Tl(I) removal. The re-dissolution of Tl compounds and ion exchange of Tl cations with proton were the main mechanisms for adsorbent regeneration. Given the fast oxidation rate, high adsorption capacity, steady reusability and facile separability, this magnetic biochar-hypochlorite technique is a promising means for Tl(I) removal from wastewater. The catalytic hypochlorite oxidation induced by the magnetic biochar has also great potential to the effective removal of other pollutants.

Synthesis of manganese dioxide with different morphologies for thallium removal from wastewater.

Manganese dioxide (MnO2) with different morphologies (tube-, wire-, rod-, and flower-like) was synthesized via hydrothermal method and then applied for thallium (Tl) removal from wastewater. During material synthesis, short reaction time (6 h) and low temperature (110 °C) were prone to form polycrystalline flower-like birnessite type MnO2, while long reaction time (24 h) and high temperature (240 °C) were inclined to produce polycrystalline wire-like birnessite type MnO2. Moderate reaction time (12 h) with low temperature at 120 °C/140 °C led to formation of mono-crystalline rod- and tube-like α-MnO2, respectively. Wire-like MnO2 was the most effective adsorbent for Tl(I) removal from both the synthetic and industrial wastewaters. The MnO2 of four morphologies exhibited similarly high Tl(III) removal owing to the precipitation of Tl(III) as Tl2O3. Effective Tl(I)/Tl(III) removal (99%) was achieved with wire-like MnO2 at an initial pH of 6 and an adsorbent dosage of 0.25 g/L. The Tl(I)/Tl(III) adsorption can be described with the pseudo-second-order kinetic. The Tl(I) removal was best fitted with the Freundlich model, with a maximum adsorption capacity of 450 mg/g. While the Tl(III) removal was best fitted with the Langmuir model, with an extremely high capacity of 6250 mg/g. Based on the results from XRD, SEM-EDS, FT-IR, and XPS analyses, the mechanisms of Tl removal using wire-like MnO2 are primarily surface complexation and oxidative precipitation. Overall, wire-like MnO2 is a highly effective adsorbent for Tl removal from both synthetic and actual wastewaters.

Mechanism of uranium release from uranium mill tailings under long-term exposure to simulated acid rain: Geochemical evidence and environmental implication.

To date, there is not sufficient knowledge to fully understand the occurrence, transport and fate of residual uranium (U) from uranium mill tailings (UMT). Herein this study investigated different U release behaviors from natural UMT (without grinding) under four simulated acid rain (pH = 2.0-5.0) compared with controlled scenario (pH = 6.0) for 25 weeks. The results showed that the most notable U release was observed from UMTpH2.0, followed by UMTpH3.0 whereas a nonlinear relationship between pH and U release was observed from UMTpH4.0-6.0. The divergence of U release behaviors was attributed to the presence of minerals such as calcite and clinochlore. Autunite, a secondary mineral formed after leaching, might regulate U release in UMTpH3.0-6.0. Fick theory model revealed the shift of U release mechanism from surface dissolution to diffusion transport for UMTpH2.0, UMTpH3.0 and UMTpH5.0 at varied stage, whereas UMTpH4.0 and UMTpH6.0 displayed univocal dissolution and diffusion mechanism, respectively. This study highlights the necessity of performing long-term leaching tests to detect the "shift event" of leaching kinetics and to better understand the mechanism of U release influenced by mineralogy of the natural UMT under simulated acid rain conditions, which is conducive to developing UMT management strategies to minimize the risk of U release and exposure.

Removal of thallium from aqueous solutions using Fe-Mn binary oxides.

In this study, Fe-Mn binary oxides, which harbor the strong oxidative power of manganese dioxide and the high adsorption capacity of iron oxides, were synthesized for Tl(I) removal using a concurrent chemical oxidation and precipitation method. The adsorption of Tl onto the Fe-Mn adsorbent was fast, effective, and selective, with equilibrium sorption reaching over 95% under a broad operating pH (3-12), and high ionic strength (0.1-0.5mol/L). The adsorption can be well fitted with both Langmuir and Freundlich isotherms, and the kinetics can be well described by the pseudo-second-order model. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra suggest that surface complexation, oxidation and precipitation were the main mechanisms for the removal of Tl. This study shows that the Fe-Mn binary oxides could be a promising adsorbent for Tl removal.

Historical trends and ecological risks of polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs) in a mangrove in South China.

While the production of polybrominated diphenyl ethers (PBDEs) was gradually phased out in the last decade, they may still pose hidden danger to the environment due to their toxicity and persistence. On the other hand, alternative halogenated flame retardants (AHFRs) have been increasingly used as substitutes for PBDEs and may further worsen environmental health. To determine the environmental impact of PBDEs and AHFRs, we examined the historical trends and ecological risks of PBDEs and AHFRs in a typical industrialized city in South China by measuring their concentrations in mangrove sediment. Results showed that the concentrations of PBDEs increased abruptly from 1997 to 2009 due to the use of commercial deca-BDE mixture, but were stabilized in recent years. The concentrations of AHFRs, mainly contributed by decabromodiphenyl ethane (DBDPE), kept increasing from 1997 onwards. Based on the temporal trends, DBDPE is predicted to be predominant over BDE 209 in future. Despite the observed similar concentration between BDE 209 and DBDPE, the former posed a high ecological risk, while the ecological risk of the latter was negligible. Therefore, more attention is required to manage the contamination of BDE 209 in the environment.

Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins.

Simultaneous removal of thallium (Tl) and chloride from a highly saline industrial wastewater was investigated using modified anion ion exchange resins. The removal of thallium was mainly driven by the exchange of Tl-chlorocomplex (TlCl4-) formed in the oxidation of thallous (Tl (I)) to thallic ion (Tl (III)) by hydrogen peroxide (H2O2) under saline conditions. Over 97% of thallium and chloride removal was achieved using the modified resins, with a wide optimal conditions found to be H2O2 dosage 1.0-25.0mL/L, pH 1.6-4.3, and flow rate 0.5-4.7mL/L. The modified resins had an exchange capacity of 4.771mg Tl/g dry resins for thallium and 1800mg Cl/g dry resins for chloride. Stable regeneration could be achieved with the modified resins: over 97% of thallium and 90% of chloride can be eluted using Na2SO3 solution and alternating hot (60°C) H2SO4 and cold (25°C) water, and over 98% removal of thallium and chloride was achieved after five consecutive regeneration cycles.