[Preparation of Modified Watermelon Biochar and Its Adsorption Properties for Pb(â ¡)].

In this study, watermelon rind was used as a raw material to modify watermelon rind biochar (MBC) with ammonium sulphate[(NH4)2S] for adsorption of Pb(Ⅱ) ions. The effects of solution pH, adsorption time, adsorbent addition amount, initial mass concentration of Pb(Ⅱ) ions, and ionic strength on the adsorption of Pb(Ⅱ) ions were investigated. The results show that the saturated adsorption time was 5 h, the optimum pH of the adsorption reaction was 6, and when the initial mass concentration of Pb(Ⅱ) ions were 1000 mg·L-1, and the amount of adsorbent was 2.0 g·L-1. The maximum adsorption amount of MBC to Pb(Ⅱ) ions can reach 97.63 mg·g-1, which is significantly higher than unmodified watermelon husk biochar (BC). The adsorption of Pb(Ⅱ) ions by modified watermelon biochar was in accordance with the Langmuir isotherm adsorption model and the pseudo second-order kinetic model, which proves that adsorption is dominated by monolayer chemical adsorption. The desorption of MBC after adsorption of Pb(Ⅱ) ions was carried out using a sodium hydroxide solution to study the reusability of MBC, and the adsorption amount was still 64.74 mg·g-1 in the sixth cycle. Characterization and analysis of adsorbents by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption, scanning electron microscopy-energy spectroscopy, zeta potential analysis, and X-ray diffraction (XRD) were carried out, which showed that the adsorption mechanism is mainly that MBC oxygen- and MBC sulfur-containing groups adsorb Pb(Ⅱ) through complexation and precipitation. Therefore, ammonium sulfide modified watermelon rind biochar can be used as a highly efficient lead adsorbent.

[Isolation, identification of methyl tert-butyl ether degradation strain and its degradation kinetics].

A methyl tert-butyl ether degradation strain A1 was isolated from the soil under an old Gingko tree. It was identified preliminarily as Comamonas testosterone by 16S rDNA sequence analysis. The main factors including inoculation amount of microbes, pH, temperature and MTBE concentration that may affect the degradation efficiency of MTBE were further studied. The results indicated that the optimum conditions were as following: pH 7.0, temperature 25 degrees C, inoculation amount of microbes was 2 mL (D600 = 2.523 A), initial MTBE concentration 50 mg/L. Under that condition, MTBE can be reduced by 98.89% with seven days (compared with the blank, the volatilization of MTBE was 46.55%). In addition, the biodegradation process of MTBE can be well described by enzymatic reaction of high concentration inhibition, with the maximum substrate utilization rate 0.872 d(-1), Michaelis-Menten constant 7.832 mg x L(-1), inhibitory constant 130.75 mg x L(-1) respectively.

[Degradation of methyl tert-butyl ether (MTBE) by O3/H2O2].

The degradation of methyl tert-butyl ether (MTBE) in water solution has been studied using the combination of ozone/hydrogen peroxide in a bubble column. Effects of air (containing O3) currents, quantities of H2O2, initial concentrations of MTBE, pH values and temperatures on the oxidation of MTBE have been tested, and it is implicated that under the conditions of initial MTBE concentration of 10 mg x L(-1), air current of 0.5 L x min(-1), pH 6.5, 293 K and 2.4 mg x L(-1) H2O2 addition, MTBE can be reduced by 75.5% and the removal rate of COD reaches 68.0% within 30 min. The main of degradation products identified are tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone (AC) and methyl acetate (MA). On the basis of that, the probable mechanism and pathway of the oxidation of MTBE by ozone/hydrogen peroxide have been proposed.