Physical characteristics of sintered fly ash aggregate containing clay binders

A comprehensive research has been conducted to explore the influence of sintering on the properties of fly ash aggregate containing clay binders (bentonite and kaolinite). Fly ash aggregate containing clay binders, have been subjected to various sintering temperatures at different durations of 700?C1400?°C and 15?C120?min, respectively. The variation in aggregate properties, viz strength, water absorption, density and shrinkage during sintering, have been determined and discussed. In addition to these, the uniformity of sintering and rate of water absorption of sintered aggregate were also determined. No significant changes in aggregate properties were observed for aggregate sintered up to 900?°C, due to the insufficient sintering temperature range. However, the aggregate properties substantially enhanced for temperature above 1000?°C, which is attributed to the activation of liquid phase sintering. For temperatures between 1000 and 1300?°C, the aggregate with bentonite shows significant increase in shrinkage (30?%), density (density ratio 0.70), higher ten percent fines value (TPFV) (6.13?tonne), reduction in porosity (35?%), and water absorption of 4?%. However, at 1400?°C, the aggregate properties degraded due to the decomposition of mineral phases in bentonite. For aggregates with kaolinite, highest TPFV of 8.5?tonne with lowest water absorption of 2?% have been observed at 1400?°C. The presence of a higher amount of interconnected pores for aggregates sintered between 700 and 1000?°C leads to a higher rate of water absorption and then reduces to 30?% for temperatures between 1200 and 1300 and 1200 to 1400?°C for bentonite and kaolinite aggregates, respectively. This reduction is due to the reduced interconnected pores. Duration of sintering has no impact on the aggregate properties for temperatures up to 800 and 1000?°C for aggregates with bentonite and kaolinite, respectively. However, between 1000 and 1400?°C, there has been considerable improvement in the aggregate properties for increasing duration up to 60?min. In comparison, during sintering, aggregates with bentonite possessed better properties for temperature less than 1000?°C, whereas aggregates with kaolinite exhibited superior properties between 1100 and 1400?°C.     

Procedures adopted for the laboratory cultivation of Trichodesmium erythraeum

The present paper describes the procedures adopted for axenic or pure cultivation of the marine blue-green alga Trichodesmium erythraeum (Ehr.)¹ in the laboratory. Strains of T. erythraeum were isolated from the nearshore waters of the Bay of Bengal (11°29 N 79°49 E) during the pre-bloom period in March, 1965, at a depth of 9 to 12m. Modified, enriched, Erdschreiber medium was used for laboratory cultivation of T. erythraeum. A differential concentration of streptomycin 6 mg/100 ml, tetracycline 5 mg/100 ml and sulfadiazine 4 mg/100 ml was used to inhibit the microbial growth in cultures. Difficulties experienced in the initial culture stages of T. erythraeum and the necessary specific instructions employed are described in detail.     

Click chemistry approach to conventional vegetable tanning process: accelerated method with improved organoleptic properties

Click chemistry approaches are tailored to generate molecular building blocks quickly and reliably by joining small units together selectively and covalently, stably and irreversibly. The vegetable tannins such as hydrolyzable and condensed tannins are capable to produce rather stable radicals or inhibit the progress of radicals and are prone to oxidations such as photo and auto-oxidation, and their anti-oxidant nature is well known. A lot remains to be done to understand the extent of the variation of leather stability, color variation (lightening and darkening reaction of leather), and poor resistance to water uptake for prolonged periods. In the present study, we have reported click chemistry approaches to accelerated vegetable tanning processes based on periodates catalyzed formation of oxidized hydrolysable and condensed tannins for high exhaustion with improved properties. The distribution of oxidized vegetable tannin, the thermal stability such as shrinkage temperature (T _s) and denaturation temperature (T _d), resistance to collagenolytic activities, and organoleptic properties of tanned leather as well as the evaluations of eco-friendly characteristics were investigated. Scanning electron microscopic analysis indicates the cross section of tightness of the leather. Differential scanning calorimetric analysis shows that the T _d of leather is more than that of vegetable tanned or equal to aldehyde tanned one. The leathers exhibited fullness, softness, good color, and general appearance when compared to non-oxidized vegetable tannin. The developed process benefits from significant reduction in total solids and better biodegradability in the effluent, compared to non-oxidized vegetable tannins.     

Occurrence,toxicity and remediation of polyethylene terephthalate plastics. A review

Environmental Chemistry Letters - Polyethylene terephthalate is a common plastic in many products such as viscose rayon for clothing, and packaging material in the food and beverage industries....     

Modeling of lead and cadmium uptake by plants in the presence of surfactants

The mechanism of simultaneous uptake of Cd(II) and Pb(II) by Indian mustard (Brassica juncea) in presence of Triton X-100 and Tween 80 was investigated. The metal uptake data were analyzed according to the linear as well as the nonlinear Langmuir- and Freundlich-type models. The modeling efficiency (EF) and the root mean square error (RMSE) were used to evaluate the models prediction. Compared to the linear and the Langmuir-type models, the Freundlich-type model marginally exhibits a better fit for the biosorption of solubilized Cd(II) by surfactants as reflected by higher EF and lower RMSE values. The values of observed Pb(II) uptake were in close agreement with the predictions of the Freundlich-type model than for the Langmuir-type model.     

Reuse potential of low-calcium bottom ash as aggregate through pelletization

Coal combustion residues which include fly ash, bottom ash and boiler slag is one of the major pollutants as these residues require large land area for their disposal. Among these residues, utilization of bottom ash in the construction industry is very low. This paper explains the use of bottom ash through pelletization. Raw bottom ash could not be pelletized as such due to its coarseness. Though pulverized bottom ash could be pelletized, the pelletization efficiency was low, and the aggregates were too weak to withstand the handling stresses. To improve the pelletization efficiency, different clay and cementitious binders were used with bottom ash. The influence of different factors and their interaction effects were studied on the duration of pelletization process and the pelletization efficiency through fractional factorial design. Addition of binders facilitated conversion of low-calcium bottom ash into aggregates. To achieve maximum pelletization efficiency, the binder content and moisture requirements vary with type of binder. Addition of Ca(OH)₂ improved the (i) pelletization efficiency, (ii) reduced the duration of pelletization process from an average of 14–7 min, and (iii) reduced the binder dosage for a given pelletization efficiency. For aggregate with clay binders and cementitious binder, Ca(OH)₂ and binder dosage have significant effect in reducing the duration of pelletization process.     

Influence of pelletization process on the properties of fly ash aggregates

A pelletization process is used to manufacture artificial lightweight coarse aggregate using fly ash. Pelletization depends on the size of particles and their distribution, the wettability of particles and moisture content, along with the process related parameters. A review indicates that only limited studies have been reported on the pelletization of fly ash aggregates. The influence of the following parameters has been studied: (i) speed of revolution of pelletizer disc, (ii) angle of pelletizer disc, (iii) moisture content, and (iv) duration of pelletization. Fractional factorial experiments using the concept of Taguchi's orthogonal array is used in this study, which uses an orthogonal array table to arrange multifactor experiments and uses statistical methods to analyze the experimental results. The relative influence of the factors above and their interaction effects on the strength, water absorption and size growth of fly ash aggregates are discussed.     

Experimental study relating to red tide

In laboratory cultures, increased growth of Trichodesmium erythraeum was induced by the addition of gibberellic acid (GA). Addition of 2.0 mg/l GA to basal medium increased the initial concentration of 62 to 68 cells/10 ml to 450 to 950 cells/10 ml in 7 days, while no cell division occurred in control cultures. Addition of inorganic phosphate and nitrate have very little growth promoting effects; during a period of 7 days, the initial concentration of 62 cells/10 ml increased to only 74 to 80 cells/10 ml. These results suggest that red tide outbreaks in tropical oceans may be caused by growth promoting substances.     

CAPITAL COSTS OF RURAL WATER SYSTEMS: AN EMPIRICAL APPROACH1

ABSTRACT: In the last two decades the federal government has provided substantial capital to construct rural water distribution systems. Loans at subsidized interest rates and front-end grants through the Farmers Home Administration have been the main source of this capital. Recent federal policy redirections have reduced substantially the availability of grants and subsidized loans. Because of design and material differences, capital cost estimates from urban systems are not uniformly applicable to rural water services. This study presents an econometric analysis of capital costs, using Illinois rural water system construction contract bids. Cost equations by systems components representing 90 percent of capital costs are estimated. The type of information developed here can be used in initial planning and optimization design models contributing to the efficient provision of rural water services.