B.C. Meikap

Response surface modeling and optimization of chromium(VI) removal from aqueous solution using Tamarind wood activated carbon in batch process

The present paper discusses response surface methodology (RSM) as an efficient approach for predictive model building and optimization of chromium adsorption on developed activated carbon. In this work the application of RSM is presented for optimizing the removal of Cr(VI) ions from aqua solutions using activated carbon as adsorbent. All experiments were performed according to statistical designs in order to develop the predictive regression models used for optimization. The optimization of adsorption of chromium on activated carbon was carried out to ensure a high adsorption efficiency at low adsorbent dose and high initial concentration of Cr(VI). While the goal of adsorption of chromium optimization was to improve adsorption conditions in batch process, i.e., to minimize the adsorbent dose and to increase the initial concentration of Cr(VI). In the adsorption experiments a laboratory developed Tamarind wood activated carbon made of chemical activation (zinc chloride) was used. A 2(4) full factorial central composite design experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R(2)=0.928) and satisfactory prediction second-order regression model was derived. Maximum chromium removal efficiency was predicted and experimentally validated. The optimum adsorbent dose, temperature, initial concentration of Cr(VI) and initial pH of the Cr(VI) solution were found to be 4.3g/l, 32 degrees C, 20.15 mg/l and 5.41 respectively. Under optimal value of process parameters, high removal (>89%) was obtained for Cr(VI).

Optimization of production conditions for activated carbons from Tamarind wood by zinc chloride using response surface methodology.

The low-cost activated carbon was prepared from Tamarind wood an agricultural waste material, by chemical activation with zinc chloride. Activated carbon adsorption is an effective means for reducing organic chemicals, chlorine, heavy metals and unpleasant tastes and odours in effluent or colored substances from gas or liquid streams. Central composite design (CCD) was applied to study the influence of activation temperature, chemical ratio of zinc chloride to Tamarind wood and activation time on the chemical activation process of Tamarind wood. Two quadratic models were developed for yield of activated carbon and adsorption of malachite green oxalate using Design-Expert software. The models were used to calculate the optimum operating conditions for production of activated carbon providing a compromise between yield and adsorption of the process. The yield (45.26 wt.%) and adsorption (99.9%) of the activated carbon produced at these operating conditions showed an excellent agreement with the amounts predicted by the models.

Column performance of granular activated carbon packed bed for Pb(II) removal

The excessive release of lead from lead acid batteries, smelting plant into the environment is a major concern worldwide. Adsorption process is among the most effective techniques for lead removal from wastewater and activated carbon has been widely used as an adsorbent. In this paper an attempt has been made to investigate the adsorption behaviour of Pb(II) from aqueous systems onto granular activated carbon using the batch mode and continuous mode in a packed bed column with more successive service and regeneration. The experiments were performed at constant temperature and dimensions of column and packed bed of granular activated carbon with variation of flows through the bed and concentrations of lead solutions. Breakthrough points were found out for the adsorption of lead on the adsorbent using continuous-flow column operation by varying different operating parameters like hydraulic loading rate from 4 to 16 m(3)/h m(2) and feed concentrates from 20 to 60 mg/l. Granular activated carbon column regeneration using 0.5 M concentration of HNO(3) has been investigated. Results indicate encouraging performance towards removal of Pb(II).

Removal of methylene blue from wastewater using fly ash as an adsorbent by hydrocyclone

The excessive release of color into the environment is a major concern worldwide. Adsorption process is among the most effective techniques for color removal from wastewater and fly ash has been widely used as an adsorbent. Therefore, this study was carried out to understand the adsorption behavior of methylene blue from aqueous systems onto fly ash using the continuous mode. Continuous mode sorption experiments were carried out to remove methylene blue from its aqueous solutions in hydrocyclone equipment. The experiments were performed at constant temperature and dimensions of hydrocyclone with variation of flows through the equipment, concentrations of methylene blue solutions and fly ash concentration, respectively. A maximum removal of 58.24% was observed at adsorbent dosage of 900 mg/l at pH 6.75 for an initial methylene blue concentration of 65 mg/l.

Air Dense Medium Fluidized Bed for Dry Beneficiation of Coal: Technological Challenges for Future

Air dense medium fluidized bed (ADMFB) offers a better alternative approach for dry coal beneficiation. In recent years, there has been a rapid advancement in the understanding of fluidized bed behavior and a great deal of work has been done to make this process competitive with conventional wet beneficiation processes. At the same time, much information is available in the general technical literature concerning various aspects of ADMFB; however, this is often uncoordinated information and widely dispersed. So, it is necessary to provide the adequate information systematically, which offers researchers an effective and easy way to obtain specific details. This review critically evaluates the understanding of different operating parameters that affect the cleaning performance of this equipment. Then, following the discussion of different operating parameters, we describe three recent practical developments in ADMFB: the dual-density fluidized bed, vibrated fluidized bed, and magnetically stabilized fluidized bed. Finally, some challenging issues that need special attention are suggested in the conclusion for further improvement of this process.

Modeling of a novel multi-stage bubble column scrubber for flue gas desulfurization

Abstract Desulfurization of flue gases from various chemical industries in a techno-econo-enviro manner is a demanding technology. The concentrations of sulfur dioxide in and around these plants overshoot the danger point. In the present investigation, an attempt has been made for wet flue gas desulfurization using water as the absorbing medium in a newly developed scrubber. Prediction of SO 2 removal efficiency is very important for selection of pollution control equipment. The present paper reports on both the modeling and detailed experimental investigations on the scrubbing of SO 2 in the modified multi-stage bubble column scrubber (MMSBCS) using water. Experimental results show that almost 100% removal efficiency of SO 2 , can be achieved in the present system without additives or pre-treatment. A comparison has been made between the predicted and experimental percentage removal efficiency of SO 2 . Experimental results are in excellent agreement with the predicted values from the model.

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.

Fly-ash removal efficiency in a modified multi-stage bubble column scrubber

Bubble columns are being widely used in chemical process industries for its various advantages and simplicity. A pilot plant novel multi-stage bubble column wet scrubber has been conceived, designed and fabricated. This novel scrubber has been used as dust collecting wet scrubber in presence of other gaseous and vapor pollutants. This paper reports on the detailed experimental investigations carried out on the scrubbing of fly-ash in this novel wet scrubber using water as the scrubbing medium. It has been found that the present system yielded very high efficiency for the scrubbing of fly-ash. In most cases, the fly-ash removal efficiency is more than 95% and many cases approaches 99.5%. A correlation has been developed for prediction of particulate (fly-ash) removal efficiency. The scale-up of this pilot plant in Indian thermal power plant shows excellent performance and meets the stringent pollution control standards. Attempt has also been made to install the above wet scrubber in Indian Thermal Power Plants and Ceramic Industries to combat particulate pollution control and found excellent performance.

Statistical modelling and optimization of hydrolysis of urea to generate ammonia for flue gas conditioning

The present study is concerned with the technique of producing a relatively small quantity of ammonia which can be used safely in a coal-fired thermal power plant to improve the efficiency of electrostatic precipitator by removing the suspended particulate material mostly fly ash, from the flue gas. In this work hydrolysis of urea has been conducted in a batch reactor at atmospheric pressure to study the different reaction variables such as reaction temperature, initial concentration and stirring speed on the conversion by using design expert software. A 2(3) full factorial central composite design (CCD) has been employed and a quadratic model equation has been developed. The study reveals that conversion increases exponentially with an increase in temperature, stirring speed and feed concentration. However the stirring speed has the greatest effect on the conversion with concentration and temperature exerting least and moderate effect respectively. The values of equilibrium conversion obtained through the developed models are found to agree well with their corresponding experimental counterparts with a satisfactory correlation coefficient of 93%. The developed quadratic model was optimized using quadratic programming to maximize conversion of urea within experimental range studied. The optimum production condition has been found to be at the temperature of 130 degrees C, feed concentration of 4.16 mol/l and stirring speed of 400 rpm and the corresponding conversion, 63.242%.

Kinetic studies on hydrolysis of urea in a semi-batch reactor at atmospheric pressure for safe use of ammonia in a power plant for flue gas conditioning

With growing industrialization in power sector, air is being polluted with a host of substances-most conspicuously with suspended particulate matter emanating from coal-fired thermal power plants. Flue gas conditioning, especially in such power plants, requires in situ generation of ammonia. In the present paper, experiments for kinetic study of hydrolysis of urea have been conducted using a borosil glass reactor, first without stirring followed by with stirring. The study reveals that conversion increases exponentially with an increase in temperature and feed concentration. Furthermore, the effect of stirring speed, temperature and concentration on conversion has been studied. Using collision theory, temperature dependency of forward rate constant has been developed from which activation energy of the reaction and the frequency factors have been calculated. It has been observed that the forward rate constant increases with an increase in temperature. The activation energy and frequency factor with stirring has been found to be 59.85 kJ/mol and 3.9 x 10(6)min(-1) respectively with correlation co-efficient and standard deviation being 0.98% and +/-0.1% in that order.