A reply to a discussion by D.J. Cook of the paper a reaction product of lime and silica from rice husk asha star, open

Abstract is not available.

Pozzolanic properties of rice husk ash, burnt clay and red mud

In this paper materials like rice husk ash, burnt clay and red mud are examined for their pozzolanic properties. Rice husk ash, obtained from various sources, is analysed by X-ray diffraction. Compressive strength properties of lime-pozzolana mortars with rice husk ash, burnt clay and red mud as pozzolana are studied. Influence of grinding of rice husk ash and intergrinding with lime are also investigated. Combination pozzolana with partial replacement of burnt clay and red mud by rice husk ash are examined for their pozzolanic properties. Long term strength behaviour of lime-pozzolana mortars is investigated to understand the durability of lime-pozzolana cements.

Reactivity of rice husk ash

Effect of lime:silica ratio on the kinetics of the reaction of silica with saturated lime has been investigated. Below C/S=0.65 the reaction does not proceed to completion and even in the presence of a large excess of silica only 90% lime is consumed. A parameter, lime reactivity index, has been defined to quantity the reactive silica present in rice husk ash. The product of the reaction between rice husk ash and saturated lime is a calcium hydrosilicate, C---S---H(I)**. The fibrilar structure and the hollow tubular morphology of the fibres of C---S---H, have been explained by a growth mechanism, where the driving force is osmotic pressure.

Reaction product of lime and silica from rice husk ash

Rice husk ash (about 95% silica) with known physical and chemical characteristics has been reacted with lime and water. The setting process for a lime-excess and a lime-deficient mixture has been investigated. The product of the reaction has been shown to be a calcium silicate hydrate, C-S-H(I)+ by a combination of thermal analysis, XRD and electron microscopy. Formation of C-S-H(I) accounts for the strength of lime-rice husk ash cement.

Silica from rice husk through thermal decomposition

The thermal decomposition characteristics of rice husk have been investigated by dynamic thermoanalytical techniques: DTA, TG, DTG and isothermal heating. The observed thermal behaviour is explained on the basis of a superposition of the decomposition of cellulose and lignin, which are the major organic constituents of rice husk. Morphological features of silica in husk as well as the ash are examined by scanning electron microscopy. Silica in the residual ash has been characterised by X-ray diffraction and infrared spectroscopy. Controlled thermal decomposition of rice husk has been shown to be a convenient method for the liberation of silica.

Rice husk filtrate as a nutrient medium for the growth of Desulfotomaculum nigrificans: characterisation and sulfate reduction studies

The filtrate obtained by interacting a known amount of rice husk with deionised, Milli-Q water was assessed as a carbon source and nutrient medium for the growth of Desulfotomaculum nigrificans, a typical sulfate-reducing bacterium. The filtrate contained essential growth constituents such as magnesium, potassium, phosphorous apart from calcium, sodium, chloride and sulfate ions. Based on the 1H and 13C NMR characterization studies, the organic composition of the components dissolved from the rice husk, was found to be: (i) 66% lignocellulosic material, (ii) 24% xylose + arabinose and (iii) 10% galactose. The growth studies indicated a 15-fold increase in the bacterial cell number in about 20 days. Nearly 81% and 66% reduction in sulfate concentration could be achieved in about 28 days, from the solutions containing initial sulfate concentrations of 550 mg/l and 1200 mg/l respectively. In both the cases studied, the iron concentration could be reduced by over 85%.

Biosorption of iron(III) from aqueous solutions using the husk of Cicer arientinum

Iron is a major pollutant released as a by-product during several industrial operations especially during acid mining of metal ores. In this paper, the use of Bengal gram husk (husk of channa dal, Cicer arientinum) in the biosorption of Fe(III) from aqueous solutions is discussed. Parameters like agitation time, adsorbent dosage and pH were studied at different Fe(Ill) concentrations. The adsorption data fit well with Langmuir and Freundlich isotherm models. The adsorption capacity (q(max)) calculated from the Langmuir isotherm was 72.16 mg of Fe(III)/g of the biosorbent at an initial pH of 2.5. Desorption Studies were performed at different concentrations of hydrochloric acid showing that quantitative recovery of the metal ion is possible. The infrared spectra of the biomass before and after treatment with Fe(III), revealed that hydroxyl, carboxyl and amide bonds are involved in the uptake of Fe(III) ions.

Studies on removal of metal ions and sulphate reduction using rice husk and Desulfotomaculum nigrificans with reference to remediation of acid mine drainage

The utility of rice husk as an adsorbent for metal ions such as iron, zinc and copper from acid mine water was assessed. The adsorption isotherms exhibited Langmuirian behavior and were endothermic in nature. The free energy values for adsorption of the chosen metal ions onto rice husk were found to be highly negative attesting to favorable interaction. Over 99% Fe3+, 98% of Fe2+ and Zn2+ and 95% Cu2+ uptake was achieved from acid mine water, with a concomitant increase in the pH value by two units using rice husk. The remediation studies carried out on acid mine water and simulated acid mine water pretreated with rice husk indicated successful growth of Desulfotomaculum nigrificans (D. nigrificans). The amount of sulphate bioreduction in acid mine water at an initial pH of 5.3 was enhanced by D. nigrificans from 21% to 40% in the presence of rice husk filtrate supplemented with carbon and nitrogen. In simulated acid mine water with fortified husk filtrate, the sulphate reduction was even more extensive, with an enhancement to 73%. Concurrently, almost 90% Fe2+, 89% Zn2+ and 75% Cu2+ bioremoval was attained from simulated acid mine water. Metal adsorption by rice husk was confirmed in desorption experiments in which almost complete removal of metal ions from the rice husk was achieved after two elutions using 1 M HCl. The possible mechanisms of metal ion adsorption onto rice husk and sulphate reduction using D. nigrificans are discussed.

Removal of hexavalent chromium using coffee husk

The potential to remove chromium(VI) from aqueous solutions through biosorption using coffee husk was investigated. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(VI) were studied. The data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity was found to be 44.95 mg/g. The Freundlich constants K-f and n were 1.027 mg/g (litre/mg)(n)] and 1.493, respectively. Desorption studies indicated the removal of 60% of the hexavalent chromium. Infrared spectral studies revealed the presence of functional groups, such as hydroxyl and carboxyl groups, on the surface of the biomass, which facilitates biosorption of Cr(VI).

Reactivity Of Silica From Rice Husk With Lime

The paper correlates the reactivity of rice husk ash with its physicochemical properties such as crystallinity, surface area, microstructure, particle size distribution, porosity and solubility. These properties, in tum, are dependent on the time-temperature conditions under which the ash is prepared. It is found that the reactivity of the ash cannot be quantified by any one of these parameters alone, though they all indicate it qualitatively. Therefore, a method for quantifying this property was developed, by which the Reactivity Index is obtained. There is only a gradual change in the reactivity index of RHA with ashing temperature, as in many other properties, like surface area, porosity and total volume of gas absorbed by unit mass of the silica ash. This reactive index is found to be useful in determining the optimum ash/lime ratios required to give the best performance for RHA-lime composites.

Rice-Husk-Ash Cement - A Review

The use of silica from rice-husk for the production of various materials, including rice-husk ash-lime binder, has gained significance. In this context, the decomposition of husk, the properties of the silica ash, including its crystallization and the ash-lime reaction, are reviewed. The mechanism of ash-lime reaction is controlled mostly by the development of osmotic pressure. For lime-deficient ash-lime mixtures the reaction is complete in the initial few days and therefore no strength development is observed for such mortars in the later ages. The use of optimum ash/lime ratio is recommended for obtaining consistently good performance for the mortar. A method for the determination of this ratio is also discussed.

CLXXX. Vegetable Proteins. I. The Proteins of Dolichos Lab Lab

The field bean (Dolichos lab lab ; Tamil name, Mochai ; Kanarese, Avarai) is a legume which is widely cultivated in South India often as a mixed crop with cereals. The kernel of the seed enters into the diet of may South Indian households, and in the Mysore State the seed are used as a delicacy when they are green for over four months in the year. The haulm, husk and pods are commonly used a fodder. As the kernel which is widely used as an article of food and considered to be very nutritious, contains about 24% of protein hitherto uninvestigated and as the quality of protein plays an important role in nutrition, the present work was undertaken.