Jiao Qu

Zinc accumulation and synthesis of ZnO nanoparticles using Physalis alkekengi L.

A field survey and greenhouse experiments were conducted using Physalis alkekengi L. to investigate strategies of phytoremediation. In addition, ZnO nanoparticles were synthesized using P. alkekengi. P. alkekengi plants grew healthily at Zn levels from 50 to 5000 mg kg(-1) in soils. The plants incorporated Zn into their aerial parts (with mean dry weight values of 235-10,980 mg kg(-1)) and accumulated biomass (with a mean dry weight of 25.7 g plant(-1)) during 12 weeks. The synthesized ZnO nanoparticles showed a polydisperse behavior and had a mean size of 72.5 nm. The results indicate that P. alkekengi could be used for the remediation of zinc-contaminated soils. Moreover, the synthetic method of synthesizing ZnO nanoparticles from Zn hyperaccumulator plants constitutes a new insight into the recycling of metals in plant sources.

Adsorption and photocatalytic degradation of bisphenol A by low-cost carbon nanotubes synthesized using fallen leaves of poplar

Bisphenol A (BPA) is an endocrine disruptor and the removal of it from contaminated water is a primary environmental issue. Here, carbon nanotubes (CNTs) were synthesized by heating leaves of poplar to 450 °C in air. The outer and inner diameters of CNTs were about 77.5 nm and 40.1 nm, which contained C, O, Na, Zn, Cu, Ca, K, Cl, and S. The effects of adsorption and photocatalysis on BPA (initial concentration was 10 mg L−1) by CNTs (10 mg CNTs were added into 1 L BPA solution) synthesized using leaves of poplar were studied. The results show that without CNTs, the degradation of BPA was about 24.5 ± 4.7% in 180 min with solar light irradiation. The complete equilibration time of adsorption/desorption of BPA onto the surface of CNTs was within 30 min, and approximately 19.7 ± 0.9% BPA was adsorbed by CNTs. Afterwards, the photodegradation efficiency of BPA was increased to 74.8 ± 3.9% with the combination of CNTs and solar light irradiation for 180 min. The photocatalytic property on BPA was caused by CNTs and the metal oxide on the surface of them. The methods have positive effects on solving environmental and ecological problems as well as the problem of high cost for preparation of photocatalyst.

THE EFFECT OF SODIUM HYDROGEN PHOSPHATE/ CITRIC ACID MIXTURES ON PHYTOREMEDIATION BY ALFALFA & METALS AVAILABILITY IN SOIL

The effect of sodium hydrogen phosphate/citric acid mixtures on enhancing phytoremediation of heavy metal-contaminated soil by alfalfa (Medicago sativa L.) and the changes of metal availability in soils were investigated. Alfalfa plants grew healthily in heavy metals-contaminated soils (collected from molybdenum mine) for 30 days. The heavy metal content was determined by ICP-OES. In this paper, it was found that: the phytoextraction efficiency of alfalfa plants was enhanced after the sodium hydrogen phosphate/citric acid mixtures were added into soil. As usual, the phosphorus can promote plants to accumulate more biomass (increasing 0.35%-24.62%) even if the availability of metals to extraction were increased by citric acid in the soil. With the treatment of sodium hydrogen phosphate/citric acid mixtures, the bioconcentration factor (BCF) values of alfalfa plants and the acid soluble fractions of heavy metals in soils were increased. The translocation factor (TF) values of all alfalfas in heavy metals were low, but the TF of As, Cr, Hg, Mo tended to increase with sodium hydrogen phosphate/citric acid mixtures. In other words, both the availability and the biological- validity of heavy metals in soils were increased after sodium hydrogen phosphate/citric acid mixtures were added into soils.

A NEW INSIGHT INTO THE RECYCLING OF HYPERACCUMULATOR: SYNTHESIS OF THE MIXED CU AND ZN OXIDE NANOPARTICLES USING BRASSICA JUNCEA L.

The mixed Cu and Zn oxide (Cu/ZnO) nanoparticles have been synthesized using Brassica juncea L. plants. The synthesized Cu/ZnO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS). It was found that the synthesized Cu/ZnO nanoparticles were corresponding to the Cu0.05Zn0.95O structure. The shapes of the synthesized ZnO nanoparticles were nonuniform, but the CuO nanoparticles showed a spherical shape. The CuO nanoparticles entered in the structures of ZnO nanoparticles. An average size of 97 nm was obtained for Cu0.05Zn0.95O. The Cu0.05Zn0.95O nanoparticles were pure. The method for synthesis of Cu0.05Zn0.95O nanoparticles using Cu hyperaccumulator (B. juncea) plants constitutes a new insight into the recycling of hyperaccumulator and provides a novel route for further development of green nanostructure syntheses.

Distribution of Heavy Metals, Chemical Fractions and Ecological Risks around a Molybdenum Mine in Liaoning Province, China

The total contents of lead, arsenic, mercury, chromium, cadmium, zinc, copper, molybdenum and nickel were determined in soils collected from mining and agricultural areas around the molybdenum mine in Liaoning Province, China. The distribution, chemical fractions and ecological risks of heavy metals in soils were investigated and assessed. It was found that: the degrees of warning for all soils, both mining industry areas and agricultural areas, were serious warning. The results meant that all soils were contaminated seriously by heavy metals. The observed scheme of chemical fractions for heavy metals in soils of different sites was as follows commonly: residual>oxidable> reducible>acid soluble. The sources of heavy metals in top soils around the mine were as follows: dust fall, residue in the open air, higher background in soil-forming process, accompaniment element, automobile exhaust, wear of tires and brakes, release of heavy metals from ore tailing, the application of pesticides and irrigation with wastewater.

Preparation of the CNTs/AG/ITO electrode with high electro-catalytic activity for 2-chlorophenol degradation and the potential risks from intermediates

A novel carbon nanotubes (CNTs)/agarose (AG)/ITO electrode with high electro-catalytic activity was prepared using a simple sol-gel method. Characterization results showed that the prepared CNTs/AG membrane, coated on the ITO conductive glass, was consisted of C and O. The electro-catalytic degradation for 2-chlorophenol (2-CP) and the influence factors were investigated. The results meant that electro-catalytic degradation for 2-CP was highly dependent on pH, bias voltage, and catalyst dosage. At pH 2, 4 V bias voltage, and 5 wt% CNTs dosage, the electro-catalytic efficiency of CNTs/AG/ITO electrode for 2-CP (20 mg/L) achieved 98% within 180 min. Afterwards, the electro-catalytic properties of recycling electrode, roles of the generated reactive oxygen species, and the reaction pathways were also investigated and proposed. In addition, the toxicities of the generated intermediates from the electro-catalytic degradation were calculated by easy methods. The results indicated that the toxicities of some intermediates were higher than the parent pollutant, especially the formation of 2-CP dimer which was seldom reported in the advanced oxidation process. The findings of using AG as the carrier and conductive adhesive for catalytic material and the assessment methods for the possible increasing risks from the intermediates were reported firstly in this paper.