Journal of Material Cycles and Waste Management - To recycle incineration bottom ash as a raw material in cement production, it is important to reduce the chlorides in the ash. Due to... 相似文献
To prepare a substrate for microbial conversion of xylose into xylitol, the culm of Sasa senanensis was hydrolyzed with dilute sulfuric acid. When the reaction temperature was fixed at 121°C, an optimum yield of xylose was
obtained by treatment with 2% sulfuric acid for 1 h. An increase in the sulfuric acid concentration or a prolonged reaction
time resulted in a decrease in the xylose yield. A fermentable substrate with a relatively high xylose concentration (36.7
g l−1) was obtained by hydrolysis with 2% sulfuric acid with a liquid-to-solid ratio of 5 g g−1. During hydrolysis at elevated temperatures, certain undesired byproducts were also generated, such as degradation products
of solubilized sugars and lignin, which are potential inhibitors of microbial metabolism. These compounds were, however, successfully
removed from the hydrolysate by treatment with activated char. 相似文献
The preparation of carbons in virgin and Ti-modified forms under controlled conditions at low temperature from plantain pseudo-stem (Musa paradisiaca) was achieved. These prepared carbons were characterized for instrumental studies such as BET, FTIR, XRD, SEM with EDS and TGA to understand the chemistry and modification. The determination of IEP and pHZPC established the presence of positive surface sites on the virgin (VMPC) and Ti-modified (TiMPC) carbons to facilitate the sorption of fluoride. The fluoride removal efficiency as a function of time, pH, dose, initial fluoride concentration, temperature, and co-ion intervention was studied. The maximum fluoride removal of about 81.2 and 97.7% was achievable with VMPC and TiMPC, respectively, after 20 min at the pH of 2.04 and continued for the equilibrium of 60 min. Temperature was found to be influential both by way of initial increase followed by a decrease in the fluoride uptake of MPCs. Regeneration was very consistent up to 7 cycles with the residual fluoride concentration below the WHO guide line of 1.5 mg L?1. Highest intervention due to hydrogen carbonate ions was observed during the fluoride removal process. Kinetic (pseudo-first-order, pseudo-second-order, and intra-particle diffusion) and isotherm models (Langmuir, Freundlich, and DKR) were checked for their compliance with the present sorption system. These low temperature synthesized MPCs are found to be effective candidates in the process of fluoride abatement in water.
Sustainable agricultural development is a necessity for sustainable economic growth and social development in Africa. Sustainable
agriculture largely depends on how effective natural and environmental resources are managed and utilized; it also depends
on the security of continuous access to such resources. This research was aimed to look into trends in agricultural productivity,
examine the persistence of the environmental insecurity, analyze the relationship between the two, and explore their links
to the national development policies. The results are discussed in the context of relevance to national development policies
and their implications on the sustainability of agriculture and rural livelihoods security. Literature survey, records collection
from the stakeholders, village level participatory assessments (PAs), observations and questionnaire survey were tools used
for data collection. The study shows significant (P < 0.01) declines in cereal crop yields, cattle milk yield and cattle calving rate, and increasing cattle mortality rate.
Elements of environmental insecurity were found to account for decline in agricultural productivity; significant (P < 0.01) proportion (68%), of 266 households interviewed, reported land resources deterioration, declining soil fertility,
and increasing drought frequencies as the causes of their low productivity. Declined fertilizer consumption and increasing
variability in rainfall amount significantly (P < 0.01) accounted for 59% and 39%, respectively, of the variations observed in total annual production of rice and maize,
which are major cereals in the study area. This study recommends measures to improve soil productivity such as improved fertilizer
application and use of organic manures along with mineral fertilizers for maintaining soil productivity; education of farmers
on sustainable use and management of land resources; and pro-poor rural policies in agricultural development and environmental
governance.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
Sneaking tactic, a male alternative reproductive tactic involving sperm competition, is generally adopted by small individuals
because of its inconspicuousness. However, large size has an advantage when competition occurs between sneakers for fertilization
of eggs. Here, we suggest that both large- and small-size advantages of sneaker males are present within the same species.
Large sneaker males of the dusky frillgoby Bathygobius fuscus showed a high success rate in intruding into spawning nests because of their advantage in competition among sneaker males
in keeping a suitable position to sneak, whereas small sneakers had few chances to sneak. However, small sneaker males were
able to stay in the nests longer than large sneaker males when they succeeded in sneak intrusion. This suggests the possibility
of an increase in their paternity. The findings of these size-specific behavioural advantages may be important in considering
the evolution of size-related reproductive traits. 相似文献
Phenol is degraded by biological treatment, however mineralization requires long time. To decrease the time and operational cost necessary for the mineralization of phenol, an optimum operation condition of the combined biological–photocatalytical treatment was investigated. The mineralization of phenol (50 mg l−1) was conducted in a flow-type biomembrane tank combined with a batch-type TiO2-suspended photocatalytic reactor. Phenol was degraded biologically to the concentration of 6.8 mg l−1, an effective concentration for further photocatalytic treatment. After the biological treatment, the biotreated phenol was treated photocatalytically to complete the mineralization of phenol. The combined treatment shortened the mineralization time compared to the biological treatment and electric cost compared to the photocatalytic treatment only. The combined treatment may be suitable for a short-time mineralization of phenol in wastewater. 相似文献
The carbonization of dehydrated johkasou sludge was examined using batch-type equipment. Based on the temperature changes in the carbonization room and the gas combustion room, the carbonization process was divided into three phases: phase I, drying the sludge; phase II, thermal decomposition of the dried sludge; phase III, after phase II. The times required for phases I and II were strongly correlated with the amounts of water and solid matter, respectively, in dehydrated sludge. The reduction rate of the sludge on completion of phase I was about 90% on average, and the decomposition rate of solid matter increased with time during phase II or phase II plus phase III until it reached about 50%. TOC concentration of the eluate from the carbonized sludge was used as an index to evaluate the progress of the carbonization process, and the highest temperature in the carbonization room was recognized as an important operational factor. The specific surface area and pore volume of carbonized sludge were smaller than those of charcoals and activated carbons by 1–3 orders of magnitude and 1–2 orders of magnitude, respectively. No elution of heavy metals was observed from any of the carbonized sludges examined. The reduced amount of carbon in dehydrated johkasou sludge was estimated to be about 25% of the decomposed organic matter. 相似文献
Polychlorinated biphenyl (PCB) residues from the sodium dispersion (SD) process were employed as the raw materials for the
production of activated carbon using KOH activation. The pore properties, such as the specific surface area and pore size
distribution, were characterized using the Barrett–Joyner–Halenda method and the Horvath–Kawazoe method based on the N2 adsorption isotherm at 77 K. The activated carbon produced showed similar adsorption capacities and specific surface areas
to the commercially available product. The effects of the activation conditions on the porosity of the activated carbon produced
were studied. The most significant factor affecting the specific surface proved to be the activation temperature. The activated
carbon produced from PCB residues from the high-temperature (423–443 K) SD process had a binary pore size distribution well
developed in the 4 nm region and in the micropore region. The pore structure of the carbon produced from PCB residues from
the low-temperature (333–393 K) SD process had a wide range of micropores and mesopores. 相似文献