Yanling Qiu

Simultaneous adsorption of lead and cadmium on MnO2-loaded resin

MnO2-loaded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb2+ and Cd2+ were simultaneously removed at pH range 5-6. Except for HPO4(2-), the high concentration coexistent ions such as Na+, K+, Cl-, NO3-, SO4(2-) and HCO3-, showed no significant effect on the removal efficiency of both Pb2+ and Cd2+ under the experimental conditions. The coexistence of Mg2+, Ca2+ caused the reduction of Cd2+ removal, but not for Pb2+. The adsorption equilibrium for Pb2+ and Cd2+ could be excellently described by the Langmuir isotherm model with R2 > 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb2+ and 21.45 mg/g for Cd2+. The adsorption processes followed the pseudo first-order kinetics model. MnO2-loaded D301 resin has been shown to have a potential to be used as an effective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.

Adsorption of arsenate on Cu/Mg/Fe/La layered double hydroxide from aqueous solutions.

A novel layered double hydroxide containing lanthanum (Cu/Mg/Fe/La-LDH) has been synthesized and used for the removal of arsenate from aqueous solutions. The purpose of incorporation of La3+ into LDHs was tried to enhance the uptake efficiency of arsenate and broaden the application field of LDHs functional materials. Effects of various physico-chemical factors such as solution pH, adsorbent dosage, contact time and initial arsenate concentrations on the adsorption of arsenate onto Cu/Mg/Fe/La-LDH were investigated. Results showed that the removal efficiency of arsenate increased with the increment of the lanthanum content in Cu/Mg/Fe/La-LDH adsorbents, and the optimized lanthanum content was 20% of the total trivalent metals composition (Fe3+ and La3+). The adsorption isotherms can be well described by Langmuir equation, and the adsorption kinetics of arsenate followed the pseudo-second-order kinetic model. Coexistent ions such as HPO4(2-), CO3(2-), SO4(2-), Cl- and NO3- exhibited obvious competition with arsenate for the adsorption on Cu/Mg/Fe/La-LDH. The solution pH significantly affected the removal efficiency, which was closely related to the change of arsenate species distribution under different pH conditions. The predominant adsorption mechanism can be mainly attributed to the processes including ion exchange and layer ligand exchange.

Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite.

Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more efficient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The effects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible affinity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption efficiency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g.

Extraction of copper from sewage sludge using biodegradable chelant EDDS

[S,S]-Ethylenediaminedisuccinic acid (EDDS), a biodegradable chelant, was used to separate the heavy metals from the sewage sludge based on chemical extraction technology. Under various conditions, the extraction experiments were carried out for the sewage sludge from Shanghai Taopu Municipal Wastewater Plant, China. The influences of pH and the concentration of EDDS on the extraction efficiency for copper (Cu) were discussed. The results showed that EDDS had higher extraction efficiency for Cu from the sewage sludge than other heavy metals. The system pH and the concentration of EDDS had a significant effect on the extraction efficiency. The extraction efficiency of Cu increased gradually with the increase of system pH and reached a higher efficiency within pH range of 3-10. The extraction efficiency maintained at approximately 70% when the pH > or = 4.5 and the molar ratio of EDDS to total heavy metals was 10:1. From the fractional analysis of the heavy metals in sewage sludge before and after the extraction, it was found that the extracted Cu mainly came from the following four fractions, i.e. water soluble, acid-soluble, reducible, and oxidizable fractions.

Extensive organohalogen contamination in wildlife from a site in the Yangtze River Delta.

The environmental and human health concerns for organohalogen contaminants (OHCs) extend beyond the 23 persistent organic pollutants (POPs) regulated by the Stockholm Convention. The current, intense industrial production and use of chemicals in China and their bioaccumulation makes Chinese wildlife highly suitable for the assessment of legacy, novel and emerging environmental pollutants. In the present study, six species of amphibians, fish and birds were sampled from paddy fields in the Yangtze River Delta (YRD) were screened for OHCs. Some extensive contamination was found, both regarding number and concentrations of the analytes, among the species assessed. High concentrations of chlorinated paraffins were found in the snake, Short-tailed mamushi (range of 200-340 μg g(-)(1)lw), Peregrine falcon (8-59 μg g(-1)lw) and Asiatic toad (97 μg g(-)(1)lw). Novel contaminants and patterns were observed; octaCBs to decaCB made up 20% of the total polychlorinated biphenyls (PCBs) content in the samples and new OHCs, substituted with 5-8 chlorines, were found but are not yet structurally confirmed. In addition, Dechlorane 602 (DDC-DBF) and numerous other OHCs (DDTs, hexachlorocyclohexanes (HCHs), polybrominated diphenyl ethers (PBDEs), hexbromocyclododecane (HBCDD), chlordane, heptachlor, endosulfan and Mirex) were found in all species analyzed. These data show extensive chemical contamination of wildlife in the YRD with a suite of OHCs with both known and unknown toxicities, calling for further in-depth studies.

Effect of ferric and bromide ions on the formation and speciation of disinfection byproducts during chlorination.

The effects of ferric ion, pH, and bromide on the formation and distribution of disinfection byproducts (DBPs) during chlorination were studied. Two raw water samples from Huangpu River and Yangtze River, two typical drinking water sources of Shanghai, were used for the investigation. Compared with the samples from Huangpu River, the raw water samples from Yangtze River had lower content of total organic carbon (TOC) and ferric ions, but higher bromide concentrations. Under controlled chlorination conditions, four trihalomethanes (THMs), nine haloacetic acids (HAAs), total organic halogen (TOX) and its halogen species fractions, including total organic chlorine (TOC1) and total organic bromide (TOBr), were determined. The results showed that co-existent ferric and bromide ions significantly promoted the formation of total THMs and HAAs for both raw water samples. Higher concentration of bromide ions significantly changed the speciation of the formed THMs and HAAs. There was an obvious shift to brominated species, which might result in a more adverse influence on the safety of drinking water. The results also indicated that high levels of bromide ions in raw water samples produced higher percentages of unknown TOBr.

Extraction of cadmium from sewage sludge using polyepoxysuccinic acid.

Abstract Polyepoxysuccinic acid (PESA), as an environmental benign biodegradable chelant, was used to remove heavy metals from the sewage sludge of Shanghai Taopu Wastewater Treatment Plant. The extraction of cadmium (Cd) from sewage sludge using aqueous solution of PESA was studied. It was found that PESA was capable of extracting Cd from the sludge, and the extraction efficiency was dependent on both pH and the concentration of the chelating reagent. The extraction efficiency decreased gradually with increasing of pH, whereas the dependency on pH decreased as the concentration of PESA increased. In the case of the high PESA to total metal ratio, e.g., 10:1, the extraction efficiency reached above 70% within the pH range from 1 to 7. The highest extraction efficiency obtained in the experiment was 78%. By comparing the contents of the heavy metals in sewage sludge before and after the extraction, it was found that the extracted Cd came mainly from the four fractions: acid-soluble, reducible, oxidizable, and water-soluble fractions.

Seasonal variation effects on the formation of trihalomethane during chlorination of water from Yangtze River and associated cancer risk assessment.

For the system of water samples collected from Yangtze River, the effects of seasonal variation and Fe(III) concentrations on the formation and distribution of trihalomethanes (THMs) during chlorination have been investigated. The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA. The results indicated that the average concentration of THMs (100.81 microg/L) in spring was significantly higher than that in other seasons, which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater. The total cancer risk in spring reached 8.23 x 10(-5) and 8.86 x 10(-5) for males and females, respectively, which were about two times of those in summer under the experimental conditions. Furthermore, it was found that the presence of Fe(III) resulted in the increased level of THMs and greater cancer risk from exposure to humans. Under weak basic conditions, about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe(III) compared with the situation without Fe(III). More attention should be given to the effect of the coexistence of Fe(III) and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention, especially in the coastland and estuaries.

Adsorption of Lead and Cadmium on Ca-Deficient Hydroxyapatite

A Ca-deficient hydroxyapatite(d-HAp) has been used to remove lead and cadmium from their mixed ions solution. The effect of pH, coexistent calcium and magnesium ions, and humic acid on the adsorption efficiency were investigated. The results showed that this d-HAp adsorbed both Cd2+ and Pb2+ efficiently within a wide pH range. The existence of humic acid reduced the removal efficiency of Cd2+ and Pb2+. The addition of Ca2+ and Mg2+ with a concentration of 500 mg/L only slightly reduced the removal efficiency. The adsorption kinetics was described by pseudo-second-order reaction model and the adsorption isotherm followed the Langmuir model.

Removal of lead from aqueous solution by hydroxyapatite/ manganese dioxide composite

A novel composite adsorbent, hydroxyapatite/ manganese dioxide (HAp/MnO2), has been developed for the purpose of removing lead ions from aqueous solutions. The combination of HAp with MnO2 is meant to increase its adsorption capacity. Various factors that may affect the adsorption efficiency, including solution pH, coexistent substances such as humic acid and competing cations (Ca2+, Mg2+), initial solute concentration, and the duration of the reaction, have been investigated. Using this composite adsorbent, solution pH and coexistent calcium or magnesium cations were found to have no significant influence on the removal of lead ions under the experimental conditions. The adsorption equilibrium was described well by the Langmuir isotherm model, and the calculated maximum adsorption capacity was 769 mg·g−1. The sorption processes obeyed the pseudo-second-order kinetics model. The experimental results indicate that HAp/MnO2 composite may be an effective adsorbent for the removal of lead ions from aqueous solutions.