Activated Rice Husk Research Articles

Durability of gamma irradiated polymer-impregnated blended cement pastes

This study is focusing on durability of the neat blended cement paste as well as those of the polymer-impregnated paste towards seawater and various concentrations of magnesium sulfate solutions up to 6 months of curing. The neat blended cement paste was prepared by a partial substitution of ordinary Portland cement with 5% of active rice husk ash (RHA). These samples were cured under tap water for 7 days. A similar paste was impregnated with unsaturated polyester resin (UPE) followed by gamma rays ranging from 10 to 50 kGy. The obtained data indicated that the polymer-impregnated specimens higher values of compressive strength than those of the neat blended cement paste. In addition, the polymer-impregnated blended cement specimens irradiated at a dose of 30 kGy and neat blended cement specimens were immersed in seawater and different concentrations of magnesium sulfate solutions namely, 1%, 3% and 5% up to 6 months. The results showed that the polymer-impregnated blended cement (OPC–RHA–UPE) paste irradiated at a dose of 30 kGy has a good resistance towards sulfate and seawater attack as compared to the neat blended cement (OPC–RHA) paste. These results were confirmed by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies.

Treatment of landfill leachate in sequencing batch reactor supplemented with activated rice husk as adsorbent

The objective of this study is to evaluate the performance of ethylenediamine-modified rice husk (MRH)-supplemented sequencing batch reactor (SBR) as compared to powdered activated carbon (PAC)-supplemented SBR in the removal of COD and nitrogen from a combined landfill leachate and domestic wastewater. The SBRs were operated with the FILL, REACT, SETTLE, DRAW and IDLE periods in the ratio of 2:12:2:1:7 for a cycle time of 24 h. The performance of the reactors was evaluated by monitoring the effluent quality as well as the concentration profiles of COD, ammonia nitrogen (AN), nitrite nitrogen and nitrate nitrogen during the REACT period of an operating cycle at various mixing ratios of the wastewaters. The results showed that equivalent performance of the MRH- and PAC-supplemented SBRs in terms of the efficiency and rate of COD and AN removal was achieved at a lower loading rate of MRH compared to that of PAC. The better performance of the MRH-supplemented SBR was postulated to be due to the presence of attached-growth biomass which is less inhibited by toxic constituents in leachate than suspended-growth biomass. Overall, MRH shows a good potential of being used as an alternative adsorbent to PAC in leachate treatment.

Análise da durabilidade do concreto de alto desempenho com adição de cinza de casca de arroz e borracha de pneu

Desde a década de 70 o Brasil vem apresentando uma crescente degradação nas suas estruturas de concreto armado. Por esta razão, inúmeras pesquisas relacionadas à durabilidade destas estruturas têm sido realizadas, visando a contribuir com a qualidade e com a redução dos custos com manutenção e reparos. Este trabalho avaliou o comportamento da durabilidade do concreto de alto desempenho com adições, substituindo parte de cimento e agregados presentes no concreto pela cinza da casca de arroz e borracha de pneu respectivamente. Foram realizados ensaios de durabilidade submetendo o concreto a diversos processos de degradação, como a ação da água, temperatura, sais e solução ácida. O estudo indicou que a durabilidade não foi comprometida com adição de sílica ativa ou cinza da casca de arroz, com a adição de borracha de pneu. De fato, a borracha mostrou-se muito eficaz no combate a ação de agentes químicos, a altas temperaturas e à entrada de água. Com a cinza da casca de arroz, apesar do maior diâmetro de suas partículas, conseguiu-se resultados similares em relação à sílica ativa.

Bioregeneration of activated carbon and activated rice husk loaded with phenolic compounds: Kinetic modeling

A kinetic model consisting of first-order desorption and biodegradation processes was developed to describe the bioregeneration of phenol- and p-nitrophenol-loaded powdered activated carbon (PAC) and pyrolyzed rice husk (PRH), respectively. Different dosages of PAC and PRH were loaded with phenol or p-nitrophenol by contacting with the respective phenolic compound at various concentrations. The kinetic model was used to fit the phenol or p-nitrophenol concentration data in the bulk solution during the bioregeneration process to determine the rate constants of desorption, k d , and biodegradation, k. The results showed that the kinetic model fitted relatively well ( R 2 > 0.9) to the experimental data for the phenol- and p-nitrophenol-loaded PAC as well as p-nitrophenol-loaded PRH. Comparison of the values of k d and k shows that k is much greater than k d . This indicates clearly that the desorption process is the rate-determining step in bioregeneration and k d can be used to characterize the rate of bioregeneration. The trend of the variation of the k d values with the dosages of PAC or PRH used suggests that higher rate of bioregeneration can be achieved under non-excess adsorbent dosage condition.

An economically viable method for the removal of selected divalent metal ions from aqueous solutions using activated rice husk

Biosorption of divalent metal ions, i.e. Pb(II), Cd(II), Zn(II) and Cu(II) onto rice husk activated (RHA) is investigated over pH range (1–10) via batch adsorption technique. The chemical and thermal activation of rice husk with 0.1 M HNO 3 and 1 M K 2CO 3 at 473 K enhanced the removal efficiency of RHA (35 ± 2.1–99 ± 0.5%, 33 ± 1.2–97 ± 0.6%, 32 ± 1.3–96 ± 0.8% and 28 ± 1.8–95 ± 0.9% before and after treatment, respectively). The surface area analysis of RHA by BET (Brunauer, Emmett and Teller) nitrogen adsorption method provided pore area and average pore diameter to be 542 ± 2.3 m 2 g −1 and 1076 ± 5.6 nm respectively. SEM and FTIR analyses of RHA were carried out to determine the surface morphology and functional groups involved in metal binding mechanism, respectively. The adsorption equilibrium was well described by Freundlich, Langmuir and Dubinin–Radushkevish (D–R) isotherm models by employing (4.8–48, 8.9–89, 15.3–153 and 15.7–157) × 10 −5 M solution concentrations of sorbates, respectively, at equilibrium time of 20 min at pH 6 and onto 0.2 g of sorbent. The kinetics of mass transfer and intra-particle diffusion for metal ions sorption onto RHA were studied with Lagergren and Morris–Weber kinetic models. The numerical values of thermodynamic parameters indicated the exothermic nature, spontaneity and feasibility of the sorption process. The desorption study of metal components from RHA surface was carried out with 0.1 M HCl. The sorption mechanism developed illustrates the strong interactions of sorbates with the active sites of the sorbent coupled with efficient and environmentally clean exploitation of rice waste product.

Quantification of bioregeneration of activated carbon and activated rice husk loaded with phenolic compounds

The bioregeneration efficiencies of powdered activated carbon (PAC) and pyrolyzed rice husk loaded with phenol and p-nitrophenol were quantified by oxygen uptake measurements using the respirometry technique in two approaches: (i) simultaneous adsorption and biodegradation and (ii) sequential adsorption and biodegradation. It was found that the applicability of the simultaneous adsorption and biodegradation approach was constrained by the requirement of adsorption preceding biodegradation in order to determine the initial adsorbent loading accurately. The sequential adsorption and biodegradation approach provides a good estimate of the upper limit of the bioregeneration efficiency for the loaded adsorbent in the simultaneous adsorption and biodegradation processes. The results showed that the mean bioregeneration efficiencies for PAC loaded with phenol and p-nitrophenol, respectively, obtained using the two approaches were in good agreement.

Bleaching of Mustard Oil with Some Alternative Bleaching Agents and Acid Activated Clay

An attempt was made to study the bleaching ability of some alternative adsorbents like rice husk ash (HC), acid activated rice husk ash (AC), rice husk silica (S), and Al(OH)(3) gel to replace commercial Acid Activated Clay (AAC, like Tonsil Earth: TE) for bleaching of mustard oil. Quantities of AAC used were varied from 0.5 to 2.0 % (w/w). It was used as such and along with commercial activated carbon (0.25-0.75 %, w/w), and laboratory prepared Al(OH)(3) gel, rice husk ash and silica isolated from husk. The results show that quantity of AAC to be used can be reduced to 1.00 to 1.25% (w/w) by using a combination of AAC along with rice husk ash; Al(OH)(3) gel; rice husk silica either by wet bleaching or by conventional bleaching method.

Synthesis and characterization of rice husk silica, silica-carbon composite and H3PO4 activated silica

This paper discusses synthesis and characterization of (i) rice husk based nanosilica, (ii) nanosilica carbon composite granules and (iii) phosphoric acid activated ash silica. These have been produced by burning husk in air, charring husk in hydrogen and activating husk silica with H3PO4 respectively. X-ray diffraction studies of these products reveal increasing peak width (amorphosity) with decreasing burning temperature. The activated rice husk silica transforms to crystalline product when burnt above 1000 ºC. The variation of surface area and pore volume with burning temperature show different behavior for air fired and hydrogen charred products. Activation energy associated with change in surface area for air fired and hydrogen charred samples have also been studied. Rate of variation in surface area with temperature indicate different trend. The validations of these products have been evaluated by decolorizing capacity of standard molasses and iodine solution. The adsorptive powers of these products have been found to be highest for activated silica and lowest for hydrogenated ash.

Performance of a modified multi-stage bubble column reactor for lead(II) and biological oxygen demand removal from wastewater using activated rice husk

The excessive release of wastewater into the environment is a major concern worldwide. Adsorption is the one of the most effective technique for treatment of wastewater. In this work activated carbon prepared from rice husk has been used as an adsorbent. In the present investigation a three phase modified multi-stage bubble column reactor (MMBCR) has been designed to remove lead and biochemical oxygen demand (BOD) from wastewater by means of its adsorption onto the surface of activated rice husk. The multi-staging has been achieved by hydrodynamically induced continuous bubble generation, breakup and regeneration. Under optimum conditions, maximum lead and BOD reduction achieved using activated rice husk was 77.15% and 19.05%, respectively. Results showed MMBCR offered appreciated potential benefits for lead removal from wastewater and BOD removal, even this extent of removal is encouraging and the MMBCR can be used a pretreatment unit before subjecting the wastewater to biological treatment.

Investigation on the sorption of aluminium in drinking water by low-cost adsorbents

Aluminium is one of the trace inorganic metals present in drinking water. High aluminium concentrations (3.6 to 6 mg/l) may precipitate as aluminium hydroxide affecting aquatic life. Aluminium is also a suspected agent of neurological disorders such as Alzheimer’s disease and senile dementia. The present investigation aims at the sorption of aluminium from drinking water using a low-cost adsorbent. Rice husk char and activated rice husk char were prepared and characterised for various physicochemical properties. The performance of rice husk char (RHC) was compared with other low-cost adsorbents for their aluminium removal capacity. The effect of pH, initial concentration, contact time and temperature was studied for adsorption of aluminium from water under batch conditions. The maximum adsorption capacity was observed with rice husk char at an optimal pH of 4.2. The adsorption of aluminium follows the Freundlich adsorption isotherm. The rate of aluminium adsorption was successfully described by a first-order kinetic model. The thermodynamic study revealed that aluminium adsorption is an exothermic process and the adsorption decreases with an increase in temperature.

Removal of Trivalent Arsenic (As(III)) from Contaminated Water by Calcium Chloride (CaCl2)-Impregnated Rice Husk Carbon

This paper deals with the arsenic removal ability of activated carbons produced from calcium chloride (CaCl2)-impregnated rice husks (RH). The optimum concentration of Ca2+ ions in calcium chloride solution (CCS) for impregnation was determined to be 2%, which produced ARHC(Ca-2.0). The maximum specific uptake (18.2 ± 0.05 μg/g) was obtained using ARHC(Ca-2.0) at an initial arsenic concentration of 1000 ppb. It was observed that the percentage removal and specific uptake of trivalent arsenic (As(III)) by ARHC(Ca-2.0) were ∼480% and ∼550% higher than that of activated rice husk carbon without impregnation (ARHC(Ca-0)), for an arsenic solution with an initial concentration of 100 ppb. However, using ARHC(Ca-2.0) as an adsorbent, when the initial arsenic concentration was increased from 100 ppb to 1000 ppb, the specific uptake was increased by ∼769% and the percentage removal was decreased by ∼13%. The spent adsorbent gave ∼80% desorption of the adsorbed As(III) in 5 N H2SO4. The fitness of the isotherm equa...

Adsorption of Safranin-T from wastewater using waste materials— activated carbon and activated rice husks

Textile effluents are major industrial polluters because of high color content, about 15% unfixed dyes and salts. The present paper is aimed to investigate and develop cheap adsorption methods for color removal from wastewater using waste materials activated carbon and activated rice husk—as adsorbents. The method was employed for the removal of Safranin-T and the influence of various factors such as adsorbent dose, adsorbate concentration, particle size, temperature, contact time, and pH was studied. The adsorption of the dye over both the adsorbents was found to follow Langmuir and Freundlich adsorption isotherm models. Based on these models, different useful thermodynamic parameters have been evaluated for both the adsorption processes. The adsorption of Safranin-T over activated carbon and activated rice husks follows first-order kinetics and the rate constants for the adsorption processes decrease with increase in temperature.

Concrete with highly active rice husk ash

The overall aim was to investigate the effect of highly active rice husk ash (RHA) produced by an industrial furnace on some properties of concrete. The strength, pore volume and pore distribution of concrete and the Ca(OH)2 content in concrete were investigated by JIS A 1108 (Method of test for compressive strength of concrete), a mercury instrument porosimeter, and the thermogravimetric analysis, respectively. The results show that, with RHA replacement of cement, the compressive strength of concrete is increased evidently; the average pore radius of concrete is greatly decreased, especially the portion of the pores greater than 20 nm in radius is decreased while the amount of smaller pores is increased, and the more the RHA replacement, the less the amount of Ca (OH)2 in concrete. The latter two results are the main reasons for the strength enhancement of concrete.

Adsorption of Cr(VI) From Aqueous and Electroplating Wastewater

The aim of this work was to investigate the use of activated rice husk carbon prepared by thermal activation and activated alumina in the removal of Cr(VI) from aqueous solution and electroplating wastewater through column studies. The optimum solution pH was found to be 2 for activated rice husk carbon and 4 for activated alumina in the batch process. This was further applied to the aqueous solution to optimise the column bed height, diameter and flow rate of solute. These optimised conditions were applied to the electroplating wastewater. It was observed that activated rice husk is an efficient adsorbent and comparable to commercially available activated alumina. The percent Cr(VI) removal from wastewater was 73.3% with activated rice husk and 75.3% with activated alumina after 1 h continuous flow at the rate of 5 ml min-1 from 7.5 cm bed height of adsorbent in a column having diameter 2.5 cm. A long contact time of the samples with adsorbents resulted in desorption of Cr(VI) from the adsorbent surfaces. However, the adsorption rate increased with the more available adsorbent surface sites when column bed height and diameter were greater. There was a decrease in Cr(VI) removal compared to aqueous sample due to the presence of other metal ions in the wastewater sample.

Heavy metals and adsorbents effects on activated sludge microorganisms.

The sorption of Cu(II) and Cd(II) from synthetic solution by powdered activated carbon (PAC), biomass, rice husk (RH) and activated rice husk (ARH) were investigate under batch conditions. After activated by concentrated nitric acid for 15 hours at 60-65 degrees C, the adsorption capacity for RH was increased. The adsorbents arranged in the increasing order of adsorption capacities to the Langmuir Q degree parameter were biomass > PAC > ARH > RH. The addition of adsorbents in base mix solution had increased the specific oxygen uptake rate (SOUR) activated sludge microorganisms with and without the presence of metals. The increased of SOUR were due to the ability of PAC and RH in reducing the inhibitory effect of metals on microorganisms and provide a reaction site between activated sludge microorganisms and substrates.

Effects of adsorbents and copper(II) on activated sludge microorganisms and sequencing batch reactor treatment process

Wastewater treatment systems employing simultaneous adsorption and biodegradation processes have proven to be effective in treating toxic pollutants present in industrial wastewater. The objective of this study is to evaluate the effect of Cu(II) and the efficacy of the powdered activated carbon (PAC) and activated rice husk (ARH) in reducing the toxic effect of Cu(II) on the activated sludge microorganisms. The ARH was prepared by treatment with concentrated nitric acid for 15 h at 60–65 °C. The sequencing batch reactor (SBR) systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the ratio of 0.5:3.5:1:0.75:0.25 for a cycle time of 6 h. The Cu(II) and COD removal efficiency were 90 and 85%, respectively, in the SBR system containing 10 mg/l Cu(II) with the addition of 143 mg/l PAC or 1.0 g PAC per cycle. In the case of 715 mg/l ARH or 5.0 g ARH per cycle addition, the Cu(II) and COD removal efficiency were 85 and 92%, respectively. ARH can be used as an alternate adsorbent to PAC in the simultaneous adsorption and biodegradation wastewater treatment process for the removal of Cu(II). The specific oxygen uptake rate (SOUR) and kinetic studies show that the addition of PAC and ARH reduce the toxic effect of Cu(II) on the activated sludge microorganisms.

Adsorption of Cr(VI) on activated rice husk carbon and activated alumina

The possible use of activated rice husk and activated alumina as the adsorbents of Cr(VI) from synthetic solutions and the effect of operating parameters were investigated. The activated rice husk carbon was prepared thermally in two sizes 0.3 and 1.0 mm. The maximum removal of Cr(VI) occurred at pH 2 by activated rice husk and at pH 4 by activated alumina. The amounts of Cr(VI) adsorbed increased with increase in dose of both adsorbents and their contact time. The Freundlich isotherm was applied.

Treatment of phenolic wastewater using agricultural wastes as an adsorbent in a sequencing batch reactor

The objective of this study is to investigate the potential of the activated rice husk to be used as an alternative adsorbent to powdered activated carbon (PAC) in the simultaneous adsorption and biodegradation processes under sequencing batch reactor (SBR) operation to treat synthetic wastewater containing phenol, p-methylphenol, p-ethylphenol and p-isopropylphenol. The rice husk (PRH) was activated by pyrolysis at 600 degrees C for 5 hours in a nitrogen atmosphere. Using the Langmuir model, the limiting adsorption capacities of PRH for the phenols were found to vary from 0.015-0.05 of those of PAC. The SBR reactors with and without adsorbent addition were operated with fill, react, settle, draw and idle periods in the ratio of 4:6:1:0.76:0.25 for a cycle time of 12 hours. For phenolic wastewater containing, 1,200 mg/L phenol, 1,200 mg/L p-methylphenol, 800 mg/L p-ethylphenol and 660 mg/L p-isopropylphenol, it was found that the biodegradation process alone was unable to produce effluent of quality which would satisfy the discharge standards of COD < or = 100 mg/L and phenol concentration < or = 1 mg/L. The addition of PAC in the ratio of PAC/phenolic compound at 0.095 g/g for phenol, 0.119 g/g for p-methylpheol, 0.179 g/g for p-ethylphenol and 0.220 g/g for p-isopropylphenol, can improve the effluent quality to satisfy the discharge standards. Equivalent treatment performance was achieved with the use of PRH at dosages of 2-3 times higher than those of PAC for all the phenolic wastewater studied. The increased adsorption capacity of PRH shown in the treatment indicates bioregeneration of the adsorbed surface during the treatment process.