[Properties of maize stalk biochar produced under different pyrolysis temperatures and its sorption capability to naphthalene].

Biochar was made from maize stalk under three different temperatures of 300, 500 and 700 degreeC. The elemental composition of biochar was measured by elemental analyzer. Scanning electron microscope (SEM) was used to measure the surface morphology. Sorption of naphthalene to biochar was researched by batch sorption experiments. Results showed that, with the increase of temperature, C content increased from 66. 79% to 76. 30% , H and O contents decreased from 4.92% and 19. 25% to 3. 18% and 9.53%, respectively; H/C, O/C, (O + N)/C, aromaticity and hydrophobicity increased, and polarity decreased. SEM results showed that maize stalk biochar was platy particles, and its roughness of surface increased with increasing temperature. The sorption of naphthalene on biochar followed the Lagergren pseudo-second order dynamic sorption model. Initial sorption rate and equilibrium sorption capacity increased as preparation temperatures increased at the same initial concentration of naphthalene. The isotherm sorption behavior can be described by the Freundlich model, which indicated that, as pyrolysis temperature increased, the sorption capacity of biochar increased, and nonlinearity increased first and then decreased. Biochar derived from maize stalk had distinct features when compared with other feedstocks, and its elemental composition, surface features and sorption behaviors were significantly influenced by pyrolysis temperature.

[Absorption of Hg in typical farmland soils in the Linglong gold mining area].

This study focused on the adsorption properties of Hg in 2 typical farmland soils in the Linglong gold mining area in Yantai area of China. The adsorption-desorption of Hg(II) research result showed higher adsorption of Hg in neutral soil with the value of 201.38 microg/g than that in acid soil with the value of 156.9 microg/g. The desorption of Hg in both soils was low with neutral soil showing a higher desorption ratio (13%) than acid soil (12%). Hg(II) adsorption isotherms were well fitted by Langmuir and Freundlich equation in the acid soil, with the correlation coefficient r value of 0.995 6 and 0.982 6, respectively. Langmuir equation can best describe Hg(II) adsorption isotherm in the neutral soil and acid soil, with the r value of 0.995 6 and 0.955 9, respectively. The adsorption was a bi-phasic process which started with a fast-adsorption phase and a slow-adsorption phase. The adsorption amount and rate of Hg in the fast reaction phase were much larger than that in the slow one. The adsorption kinetic can be better fitted by Elovich equation with correlation coefficient of 0.971 4 and 0.967 2, respectively. At pH 3.0 - 5.5, the equilibrium adsorption amount of Hg(II) increased with higher pH, and then decreased when the pH reached 6.5.

Effects of raw materials and bulking agents on the thermophilic composting process.

Three typical biological solid wastes, animal manure, garbage, and sewage sludge, were compared with regard for the composting process and the changes in microbial community structure. The effect of different bulking agents such as rice straw, vermiculite, sawdust, and waste paper were compared in manure compost. The differences in the microbial community were characterized by the quinone profile method. The highest mass reduction was found in garbage composting (56.8%), compared to manure and sludge at 25% and 20.2%, respectively. A quinone content of 305.2 micromol/kg was observed in the late stage of garbage composting, although the diversity index of quinone profile was 9.7, lower than that in manure composting. The predominant quinone species were found to be MK-7, which corresponds to gram positive bacteria with low G+C content such as Bacillus. The predominance of MK-7 was especially found in garbage and sludge composting process, while the increase in quinones with partially saturated long side chain was shown in late composting process of manure, which corresponded to the proliferation of Actinobacteria. The effect of different bulking agents on the composting process was much smaller than the effect of different raw materials. High organic matter content in the raw materials results in a higher microbial biomass and activity, which was connected to the high mass reduction rate.

Effect of temperature on reaction rate and microbial community in composting of cattle manure with rice straw.

The effects of temperature on microbial communities and mass reduction in composting were studied by comparing the mesophilic process with the thermophilic process of cattle manure-rice straw composting for 21 d. The respiratory quinone content (indicator of microbial biomass) continuously increased in the mesophilic process, but in the thermophilic process, it was much higher after 3 d and then decreased to the same level as that in the mesophilic process after 21 d. The diversity of quinones increased continuously in both the mesophilic and thermophilic processes with a higher value in the thermophilic process. The mesophilic microbial community was characterized by the predominance of ubiquinones and menaquinone (MK-8), which correspond to Proteobacteria and fungi. The thermophilic microbial community was characterized by the dominance of MK-7 in the initial period, and increases in the amounts of menaquinones with long and partially-saturated side chains in the later period, corresponding to Firmicutes and Actinobacteria, respectively. DNA fingerprinting by denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal RNA genes also confirmed that diversity of microbial communities increased but differently in the two processes. Our results suggest that mesophilic composting is more effective for mass reduction in cattle manure composting than thermophilic composting because of the higher decomposition activity of the microbial community characterized by the predominance of Proteobacteria and fungi.

Degradation of the seaweed wakame (Undaria pinnatifida) by a composting process with the inoculation of Bacillus sp. HR6.

Disposal of the seaweed wakame (Undaria pinnatifida) by inoculating the halotolerant bacterium Bacillus sp. HR6 was examined in an experimental scale composting system. Strain HR6 was effective in initiating the composting process of wakame, and there was a rapid increase in temperature to over 54.9-55.7 degrees C after 18-20 h. The composting process of wakame could be carried out despite a high NaCl content, 28.2 mg/g, although lower salinity resulted in a shorter lag time and higher weight reduction. In a larger scale composting process with aeration, two peaks of temperature change were found which corresponded well to oxygen consumption and CO2 emission during the process. The pH increased to 8.83 and organic materials were reduced to 93.4% after 72 h. The initial N and C contents were 3.9 and 34.0%, respectively, both of which decreased during the composting process. The changes in the viable cell numbers suggested that strain HR6 predominated before 24 h and other microorganisms including HR6 were present in a mixed state during the later period of composting. The total content of alginate (TA), 32.2% in the initial stage, decreased to 29.2% after 72 h, while water soluble alginate (WSA) increased, indicating that the solubilization and decomposition of alginate had occurred during the composting process.

[Physico-chemical and microbial properties in thermophilic composting processes of different biological solid wastes].

Characterization on the physico-chemical and microbial properties were carried out in thermophilic composting processes of 3 different biological solid wastes: manure, garbage and sludge. pH increased to above 8 and C/N ratio decreased during the process. The effect of different bulking agents on the composting process is smaller compared to different raw materials. Among the 3 different materials, garbage composting shows highest composting activity, and the mass reduction rate is 47.2%-56.8% after 14 days. Quinone content, representative of microbial biomass, increases to 359.7-472.3 mol x kg(-1) at the late composting period. However quinone diversity index only increases to 6.1-6.7, suggesting lower microbial diversity. The composting activity of cattle manure is only high at initial period and then decreases. The quinone content is high at middle period of cattle manure composting with the value of 36.3-117.0 molx kg(-1). DQ is 10.3-12.8 at initial, and increases to 18.1-22.7 during cattle manure composting. The properties of sludge composting fall in the range between cattle manure and garbage. It is suggested that the differences of the composting processes are mainly caused by organic component level in different raw materials. Suggestions on the control of composting process are also proposed based on this study.