La-EDTA coated Fe_3O_4 nanomaterial:Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FT-IR）. Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4, and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.

Ammonia volatilization and availability of Cu,Zn induced by applications of urea with and without coating in soils

Ammonia volatilization and the distribution of Cu and Zn were investigated in two types of soil treated with coated and uncoated urea.The rate of ammonia volatilization in two weeks after fertilizing with coated urea was 8% in soil 1 （soil derived from river alluvial deposits in Dongting Lake Plain） and 5.15% in soil 2 （red soil derived from quaternary red clay）,about half the rates observed when fertilizing with common urea,implying that the hydrolysis speed of the coated urea was lower than for common urea,and that the coated urea can increase nitrogen use efficacy.As for the availability of Cu and Zn,their concentrations decreased in the first week after fertilization,and then increased,which was contrary to the effect of treatment on soil pH.For example,when the pH was 7.99,there was 0.79mg/kg exchangeable Cu and 0.85mg/kg exchangeable Zn in the soil derived from river alluvial deposits in Dongting Lake Plain.However,the concentrations of exchangeable Cu and Zn were generally lower for the common urea treatments than those with the coated urea because the peak pH for the common urea treatment was greater.The concentrations of these elements correlated well with pH in the range 4–8 in second order polynomial fits.

The long-term effectiveness of ferromanganese biochar in soil Cd stabilization and reduction of Cd bioaccumulation in rice

The application of Fe-Mn-modified biochar for the remediation of Cd-contaminated soil over long time periods has been little studied.In this paper,we describe the performance of coconut-shell-derived biochar modified with ferromanganese in relation to soil Cd stabilization and rice Cd bioaccumulation during a 3-year laboratory study.Different application dosages(0.05-0.5 wt%)and different rice varieties(the early and late rice)are also considered.The results show that ferromanganese is mainly loaded in biochar pores as MnFe_(2)O_(4),and that it decreases the specific surface area(SSA)and total pore volume of biochar.Ferromanganese biochar(0.5 wt%)applied to paddy soil is more effective than the same dose of pristine biochar in decreasing the soil-exchangeable Cd fraction(27.42-41.92%vs 22.56-33.85%),predominantly by decreasing soil Eh and increasing root Fe plaques.Ferromanganese biochar application helps to reduce Cd bioaccumulation in rice,especially in the grain(up to 48.6%-61.0%),and grain Cd levels(0.2 mg/kg)are all within the acceptable limit for food security in China.It is shown that ferromanganese modification and application can maintain soil at low redox status,keep root Fe plaques at a high level,and may also increase the stability of pristine biochar.All of these effects contribute to maintaining its high remediation efficiency over a 3-year inoculation period.The results presented in this paper demonstrate the potential appli-cations of ferromanganese biochar in soil remediation and the improvement of food safety.