The interaction between a cationic dye Methylene Blue(MB) and an anionic surfactant sodium dodecyl sulfate(SDS) with the presence of Cd2+ was investigated spectrophotometrically in a certain concentration range.The spectrophotometric measurements of dye-metal ion-surfactant system were carried out.The results indicated that the SDS concentration had a significant influence on the dye spectrum,while the addition of Cd2+ hardly caused change of the maximum value of absorbance.According to this observation,we concluded that electrostatic and hydrophobic interaction between dye and surfactant occurred up to a certain level,and the homo-ions Cd2+ almost exerted no effect on the dye-surfactant complexation,establishing a theoretical foundation for simultaneous removal of organic dye and heavy metal using foam fractionation.Meanwhile,the effects of their interaction on foam performance were investigated.The results showed that the addition of Cd2+ favored the tendency to ameliorate foam properties just contrary to MB.The feasibility of foam separation for dye and heavy metal removal from simulated wastewater was also confirmed using a continuous foam fractionator.In the simultaneous removal process,with the initial SDS concentration ranging from 0.5 to 5.0mmol/L,the maximum removal efficiencies of MB and Cd2+ were obtained as 99.69% and 99.61%,respectively.The enrichment ratios were reduced from24.34 to 7.65 for MB and from22.01 to 3.35 for Cd2+.
The transformation behaviors of Pb fractions during composting of Pb-polluted waste without inoculants and with the inoculants of Phanerochaete chrysosporium were studied.Results show that the active Pb ions with high toxicity and transferability are transformed into the inactive Pb with low toxicity and transferability,confirming that Pb ions can be efficiently immobilized during composting without or with the inoculants.The soluble-exchangeable Pb in composting without inoculants reaches 49.0 mg/kg at day 60,while that with the inoculants is reduced to 0 mg/kg dry mass compost.The higher contents of organic-bound Pb (59.0 mg/kg)and residual Pb(69.2 mg/kg)with low toxicity are found after 60-day composting with inoculants,compared with those without inoculants.The above data indicate the better immobilization effect of Pb and the greater alleviation of Pb hazards in composting with the inoculants of Phanerochaete chrysosporium than without inoculants,which may be due to the more microbial biomass and the higher pH value in composting of Pb-polluted waste with inoculants.
The white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium), was inoculated during different phases of agricultural waste composting, and its effect on the fluorescence spectroscopy characteristics of humic acid (HA) was studied. The results show that the emission spectra have a sharp peak at 400 nm and a broad shoulder with the maximum centered at 460 nm. The excitation spectra have two peaks and exhibit red shift (shift to longer wavelengths) at 470 nm. The synchronous scan spectra present a number of peaks and shoulders, and the peaks at shorter wavelengths disappear gradually and form a shoulder. At the final stage of composting, the fluorescence spectra have similar shapes, but the fluorescence intensities decrease. P. chrysosporium increases the degree of aromatization and polymerization of HA when it is inoculated during the second fermentation phase, while it does not produce an obvious change on the humification degree of HA when it is inoculated during the first fermentation phase. Compared with the fluorescence spectroscopy characteristics of HA from soil, the structure of HA from compost is simpler and the activity is higher.
