Jinlong Yan

Degradation of Herbicide Mesotrione in Three Soils with Differing Physicochemical Properties from China.

The movement and fate of herbicides in soils under various environmental factors are important in evaluating their mobility and ecological impact. The effects of sterilization, solarization, and soil physicochemical properties on the degradation of herbicide mesotrione in three soils from China were evaluated using laboratory incubation method, and the degradation kinetics were also simulated using pseudo first-order reaction model. The calculated half-lives () of mesotrione were found to be 3.78- to 5.24-fold increased in sterilized soils than nonsterilized soils, which indicated that the degradation of mesotrione was strongly affected by soil microbial activity. A certain role of promoting degradation effect of natural light was found, and the values appeared to be only 7.90, 15.89, and 25.29 d in the surface of paddy soil, sandy loess, and silt clay loam, respectively. Correlation analysis between the observed first-order reaction rate constant () values and the selected soil properties revealed that the degradation of mesotrione was highly dependent on soil pH value ( > 0.992) and organic matter content ( > 0.932), but less related with clay content (<0.02 mm) with < 0.761 and nonrelated with cation exchange capacity (CEC) ( < 0.164). Data obtained in this study are helpful for further research on the prediction of the movement and fate of mesotrione in soils in limiting its environmental impact.

Effects of chemical oxidation on surface oxygen-containing functional groups and adsorption behavior of biochar

Biochar is a beneficial soil amendment but the changes in its surface properties during the aging process, especially the oxygen-containing functional groups and the associated adsorption behaviors, are not well documented. In this paper, the aged wheat straw biochar was simulated by chemical oxidation with HNO3-H2SO4 and NaOH-H2O2 systems. Characterization results showed that carbon loss and oxygen incorporation ran throughout the aging process. Surface oxygen-containing functional groups were found to be increased in all treated biochars, especially for carboxyl. Much more developed mesopores were observed in aging biochar, specific surface area was increased by 126% for biochar treated with NaOH-H2O2, and 226% for biochar treated with 40% of HNO3-H2SO4. Thermogravimetric analysis showed that the increasing oxygen-containing functional groups led to 14% and 30% mass loss by treating biochar with alkali and acid, respectively. The improved biochar surface through the increase of oxygen-containing functional groups enhanced the cadmium sorption capacity, and the sorption capacity increased by 21.2% in maximum. Roughed surface from oxidation was another reason for increasing cadmium adsorption. Results indicated that the adsorption performance of biochar on pollutant would be changed during aging process along with the changing surface properties.

Heterogeneous photodegradation of mesotrione in nano α-Fe2O3/oxalate system under UV light irradiation

The aim of this study is to investigate the behavior of mesotrione herbicide photodegradation under UV light irradiation with co-existence of iron oxides and oxalic acid. α-Fe2O3 and oxalate can set up a novel photo-Fenton-like system under UV irradiation in nature environment without H2O2 additional. The adsorption capacity of mesotrione was investigated in the dark by batch experiment, and the results were well fitted by Langmuir model. The effects of the iron oxide dosage, initial concentration of oxalic acid (C0ox), mesotrione, and initial pH on the mesotrione photodegradation were investigated. The photoproduction of hydroxyl radicals (˙OH) during the photochemical process was also examined in diverse catalytic systems. The results indicated that mesotrione photodegradation follows pseudo-first-order kinetics. The mesotrione photodegradation moves slowly in the presence of α-Fe2O3 or oxalic acid. Interestingly, we found out that mesotrione photodegradation was distinctly enhanced when α-Fe2O3 and oxalic acid co-existed under UV irradiation. We learned that the combination of α-Fe2O3 and an oxalate system is an excellent agent to accelerate mesotrione herbicide decomposition. Results from this study could be further applied in the natural environment to facilitate environmental protection.

Cobalt nanoparticles embedded in a porous carbon matrix as an efficient catalyst for ammonia decomposition

A metallic Co nanoparticle catalyst embedded in a carbon matrix was synthesized through a facile solvothermal method and subsequent thermal treatment. The synthesized Co–C precursors were calcined in N2 and limited air atmosphere respectively, which were applied for ammonia decomposition. It was found that different thermal treatments have a significant effect on the catalyst microstructure, particle size, components and catalytic performance. Compared to the Co@C-700-N sample obtained in N2 flow, the CoOx@C-700-A catalyst obtained in limited air atmosphere showed better activity with a ∼55% NH3 conversion (500 °C and GHSV = 15 000 h−1). Moreover, the structure sensitivity of NH3 decomposition over Co catalysts is proposed over a series of CoOx@C-A catalysts. With an increase of Co particle size, the catalytic activity showed an obvious decrease.

Adsorption Behaviour of Pymetrozine by Four Kinds of Biochar from Aqueous Solution

A laboratory experiment was performed to investigate the potential of biochar (BC) as an adsorbent for removing pymetrozine from aqueous solution. The adsorption data were well described by Langmuir isotherm, with maximum pymetrozine adsorption capacities of 13.8, 20.6, 11.0 and 18.8 mg g−1 for bush-, wheat straw-, peanut- and corn-derived BC in a single solution at 25 °C, respectively. The functional groups of BCs were –NH (1628.25 cm−1), –OH (3443.78 cm−1), –PO4 (1089.2 cm−1) and –C–Cl (769.23 cm−1), which were responsible for binding pymetrozine. The adsorption capacity of BC was increased by 7.2–106.4% at different solution pH (1, 3, 5 and 7). The removal efficiency increased with the addition of BCs and over 70% pymetrozine removal was observed upon addition of up to 8 g l−1. The rate of pymetrozine adsorption was fast, with 50–80% of the adsorption occurring in the first 120 minutes, followed by a much slower approach to equilibrium. The ΔG° values decreased (increasingly negative) from −165.3% to 235.9% at 298 K compared with 318 K for the adsorption of pymetrozine onto different BCs in a single solution. The study results indicate that plant residue- or agricultural waste-derived BC can act as an effective surface sorbent, but their ability to treat mixed waste streams needs to be carefully evaluated on an individual basis.

Benzothiazole heterogeneous photodegradation in nano α-Fe2O3/oxalate system under UV light irradiation

The photodegradation of benzothiazole (BTH) in wastewater with the coexistence of iron oxides and oxalic acid under UV light irradiation was investigated. Results revealed that an effective heterogeneous photo-Fenton-like system could be set up for BTH abatement in wastewater under UV irradiation without additional H2O2, and 88.1% BTH was removed with the addition of 2.0 mmol l−1 oxalic acid and 0.2 g l−1 α-Fe2O3 using a 500 W high-pressure mercury lamp (365 nm). The degradation of BTH in the photo-Fenton-like system followed the first-order kinetic model. The photoproduction of hydroxyl radicals (·OH) in different systems was determined by high-performance liquid chromatography. Identification of transformation products by using liquid chromatography coupled with high resolution tandem mass spectrometry provided information about six transformation products formed during the photodegradation of BTH. Further insight was obtained by monitoring concentrations of the sulfate ion (SO42−) and nitrate ion (NO3−), which demonstrated that the intermediate products of BTH could be decomposed ultimately. Based on the results, the potential photodegradation pathway of BTH was also proposed.

Facile Synthesis of Magnetic Nitrogen-Doped Porous Carbon from Bimetallic Metal–Organic Frameworks for Efficient Norfloxacin Removal

Magnetic nitrogen-doped porous carbon (MNPC) has been prepared via self-catalytic pyrolysis of bimetallic metal-organic frameworks (MOFs). The as-obtained MNPC showed favorable features for antibiotics adsorption such as high specific surface area (871 m2 g−1), high pore volume (0.75 cm3 g−1), porous structure, good graphitization degree, and rich N-doping. Moreover, the MNPC has magnetic properties due to the Co species, which is embedded with a high dispersion, so the absorbent can be easily separated. Based on the above excellent characteristics, the MNPC was used as the absorbent for norfloxacin (NOR) removal. The experimental maximum NOR adsorption capacity of MNPC was 55.12 mg g−1 at 298.15 K and a pH of 6.0 with an initial NOR concentration of 50 mg L−1. The data analysis of the kinetics revealed that the experimental data of NOR uptakes versus time agreed with the pseudo-second order model. The isotherm data analysis revealed the favorable application of the Freundlich model. Based on the adsorption results over a wide range of conditions, the dominant adsorption mechanisms were found to be pore-filling, electrostatic interaction, and the H-bond.

Spatial distribution of total halogenated organic compounds (TX), adsorbable organic halogens (AOX), and heavy metals in wetland soil irrigated with pulp and paper wastewater

Abstract Long-term irrigation using wastewater from paper industry may cause seriously problems to the receiving soil. This work surveyed and monitored the soil quality of a wastewater irrigation wetland system in Yancheng City, Jiangsu Province in China in 2014 and 2015. Τhe wetland soil showed different soil properties and TX, AOX, heavy metal contents after long-term wastewater irrigation. Long-term irrigation also accumulated the heavy metals such as Cu, Cd, Zn, and Pb in the wetland soil. Compared to the control, TX in the irrigated soil increased by 47.7–69.8% (2014) and 61.5–83.1% (2015). AOX varied in concentration from 1.7 to 55.0 mg kg−1 (2014) and 11.0 to 53.0 mg kg−1 (2015). The long-term irrigation of wastewater to wetland systems caused the accumulations of heavy metals, TX, and AOX in the soil and the levels of accumulations were related to several factors including soil properties, wastewater quality, and irrigation time.