ABSTRACT
The modified fly ash (MFA) was prepared through roasting the mixture of fly ash and NaOH/Ca(OH)2 at 250 â for 1.5 h. The physicochemical properties of MFA were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), surface area analyze (BET), and Fourier transform infrared spectroscopy (FTIR) techniques. Results from BET analysis showed that the BET of MFA was enlarged by 20.6 times compared with FA. Results from SEM analysis showed that the glass phase was dissolved, with a rough surface and porous structure. Results from FTIR analysis demonstrated that -OH played an important role in Cd2+ adsorption. Results from the static adsorption experiment revealed that the removal efficiency of Cd2+ reached 97.3% when 0.2 g MFA was applied while the concentration of Cd2+ was 100 mg·L-1, the solution pH was 7.0, the adsorption temperature was 25 â and the adsorption time was 90 min. In addition, the coexisting cations (K+, Na+, Mg2+, and Ca2+) might inhibit Cd2+ adsorption. Among all the cations, Ca2+ showed a most significant inhibitory effect on the removal of Cd2+. Langmuir isotherm and the pseudo-second-order kinetic models could well describe the adsorption behavior of Cd2+ on MFA, with the maximum adsorption capacity of 55.77 mg·g-1. Meanwhile, thermodynamic studies showed that Cd2+ adsorption onto MFA was spontaneous and endothermic process. MFA had better adsorption capacity than FA and had certain application pro-spects in wastewater treatment.
Subject(s)
Cadmium/chemistry , Waste Disposal, Fluid/methods , Wastewater , Water Pollutants, Chemical/chemistry , Adsorption , Coal Ash , Hydrogen-Ion Concentration , Kinetics , Spectroscopy, Fourier Transform InfraredABSTRACT
The genetic and eco-toxic effects of Cd (0-10 mg x kg(-1)) were studied with Vicia faba (broad bean) as the test species using meadow brown soil in pot experiments by means of several indexes, such as Vicia faba root tip micronucleus frequency (MCN), mitosis index (MI), and chromosomal aberrations frequency (CAF), antioxidant enzymes superoxide dismutases (SOD), peroxidases (POD), catalase (CAT) and phytohormone abscisic acid (ABA), gibberellic acid (GA3) and zeatin and zeatin riboside (Z&ZR). Results indicated the significant positive dose-response correlations were found between Cd2+ concentrations and the tested indexes (MI, MCN and CAF). Among of them, MCN is the most sensitive, and the MCN frequencies were 1.43-3.22 times higher in Cd treatment soils than that of in the controls. SOD and POD in seedling leaves of broad bean were response to the Cd stress, showing a trend of increase with Cd concentrations initially and then decreased. The CAT response to Cd in soils was opposite to that of SOD and POD. In addition, there were stimulation and inhabitation effects between Cd and ABA, GA3 and Z&ZR in lower and higher Cd concentrations. The highest contents of phytohormone (ABA, GA3 and Z&ZR) were found when Cd was at 2.5 mg x kg(-1), which was 6.6%, 4.0% and 12.6% higher than that in the control, respectively. Our study indicated that all indexes were response to the Cd stress in soils, but the sensitivity of each index was different from each other. All these indexes combined should be more efficiency in the diagnosis of geno-, and eco-toxicity of cadmium in soils.
