Adsorption of metal complex dyes from aqueous solutions by pine sawdust

An attempt to alleviate the problem caused by the presence of metal complex dyes, mostly used in textile industries, in the textile effluents was undertaken. The effects of adsorbent particle size, pH, adsorbent dose, contact time and initial dye concentrations on the adsorption of metal complex dyes by pine sawdust was investigated. Acidic pH was favorable for the adsorption of metal complex dyes. A contact time of 120 min was required to reach the equilibrium. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well the Langmuir isotherm. The monolayer adsorption capacities are 280.3 and 398.8 mg dye per g of pine sawdust for Metal Complex Blue and Metal Complex Yellow, respectively. The results indicate that pine sawdust could be employed as low-cost alternative to commercial activated carbon in aqueous solution for the removal of metal complex dyes.     

Kinetic and isothermal studies on liquid-phase adsorption of 2,4-dichlorophenol by palm pith carbon

Adsorption studies were conducted to study the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solution on palm pith carbon under varying experimental conditions such as agitation time, adsorbent dose, pH and temperature. Higher 2,4-DCP was removed with decrease in the initial concentration of 2,4-DCP and increase in amount of adsorbent used. Kinetic study showed that the adsorption of 2,4-DCP on palm pith carbon was a gradual process. Adsorption capacities were 19.16 mg/g for the particle size of 250-500 microm. The equilibrium time was 60 and 80 min for 10 and 20 mg/L and 100 min for both 30 and 40 mg/L phenol concentrations, respectively. Acidic pH was favourable for the adsorption of 2,4-DCP. Studies on pH effect and desorption showed that chemisorption seemed to play a major role in the adsorption process. Thermodynamic study showed that adsorption of 2,4-DCP on palm pith carbon was more favoured. The change in entropy (DeltaS0) and heat of adsorption (DeltaH0) of palm pith carbon was estimated as 30.72 J/mol/k and 7.16 kJ/mol, respectively. The high positive value of change in Gibbs free energy indicated the feasible and spontaneous adsorption of 2,4-DCP on palm pith carbon. The results indicated that palm pith carbon was an attractive candidate for removing phenols from wastewater.     

Experimental and kinetic studies on methylene blue adsorption by coir pith carbon

Varying the parameters such as agitation time, dye concentration, adsorbent dose, pH and temperature carried out the potential feasibility of thermally activated coir pith carbon prepared from coconut husk for removal of methylene blue. Greater percentage of dye was removed with decrease in the initial concentration of dye and increase in amount of adsorbent used. Kinetic study showed that the adsorption of dye on coir pith carbon was a gradual process. Lagergren first-order, second-order, intra particle diffusion model and Bangham were used to fit the experimental data. Equilibrium isotherms were analysed by Langmuir, Freundlich, Dubnin-Radushkevich, and Tempkin isotherm. The adsorption capacity was found to be 5.87 mg/g by Langmuir isotherm for the particle size 250-500 microm. The equilibrium time was found to be 30 and 60 min for 10 and 20 mg/L and 100 min for 30, 40 mg/L dye concentrations, respectively. A maximum removal of 97% was obtained at natural pH 6.9 for an adsorbent dose of 100 mg/50 mL and 100% removal was obtained for an adsorbent dose of 600 mg/50 mL of 10 mg/L dye concentration. The pH effect and desorption studies suggest that chemisorption might be the major mode of the adsorption process. The change in entropy (DeltaS0) and heat of adsorption (DeltaH0) of coir pith carbon was estimated as 117.20 J/mol/K and 30.88 kJ/mol, respectively. The high negative value of change in Gibbs free energy indicates the feasible and spontaneous adsorption of methylene blue on coir pith carbon.     

Removal of disperse dyes from textile wastewater using bio-sludge

Granular activated carbon (GAC) did not show any significant adsorption ability on the disperse dyes, while resting (living) bio-sludge of a domestic wastewater treatment plant showed high adsorption abilities on both disperse dyes and organic matter. The dye adsorption ability of bio-sludge increased by approximately 30% through acclimatization with disperse dyes, and it decreased by autoclaving. The deteriorated bio-sludge could be reused after being washed with 0.1N NaOH solution. Disperse Red 60 was more easily adsorbed onto the bio-sludge than Disperse Blue 60. The Disperse Red 60, COD, and BOD5 adsorption capacities of acclimatized, resting bio-sludge were 40.0+/-0.1, 450+/-12, and 300+/-10mg/g of bio-sludge, respectively. The GAC-SBR system could be applied to treat textile wastewater (TWW) containing disperse dyes with high dye, BOD5, COD, and TKN removal efficiencies of 93.0+/-1.1%, 88.0+/-3.1%, 92.2+/-2.7% and 51.5+/-7.0%, respectively without any excess bio-sludge production under an organic loading of 0.18 kg BOD5/m3-d. Furthermore, the removal efficiencies increased with the addition of glucose into the system. The dye, BOD5, COD, and TKN removal efficiencies of the GAC-SBR system with TWW containing 0.89 g/L glucose were 94.6+/-0.7%, 94.4+/-0.6%, 94.4+/-0.8% and 59.3+/-8.5%, respectively, under an SRT of 67+/-0.4 days.     

ZnCl2-Modified Activated Carbon from Biomass Coir Pith for the Removal of 2-Chlorophenol by Adsorption Process

Coir pith, a waste biomass, from coconut coir industry was used to prepare activated carbon with ZnCl₂ and employed for the removal of 2-chlorophenol (2-CP) from aqueous solution and wastewater. Zinc chloride–activated coir pith carbon (ZnCPC) was prepared by mixing coir pith with ZnCl₂ in the ratio 2:1 and carbonized at 700°C for 1 h. ZnCPC was characterized using standard physicochemical methods, Brunaver, Emmett, and Teller (BET) surface area, and scanning electron microscopy (SEM) studies. Batch mode adsorption studies were carried out to evaluate the effect of contact time, initial concentration, adsorbent dose, pH, and temperature. The Langmuir adsorption capacity Q ₀ was found to be 149.3 mg g^?1. Kinetic studies showed that the adsorption obeyed second-order and Bangham's model. Equilibrium adsorption data fit better into Langmuir, Freundlich, and D-R isotherms. pH effect and desorption studies showed that ion-exchange mechanism was involved in the adsorption process. Effect of temperature was not significant. Quantitative removal of 2-CP from synthetic wastewater was also achieved. ZnCPC is economically effective compared to commercial activated carbon, because the raw material is abundantly and freely available and it can be used effectively in the treatment of water contaminated with 2-CP.     

Removal of molybdate from water by adsorption onto ZnCl2 activated coir pith carbon

Removal and recovery of molybdate from aqueous solution was investigated using ZnCl2 activated carbon developed from coir pith. Studies were conducted to delineate the effects of contact time, adsorbent dose, molybdate concentration, pH and temperature. Two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q0) was found to be 18.9 mg molybdate/g of the adsorbent. Adsorption followed second order kinetics. Studies were performed at different pH values to find out the pH at which maximum adsorption occurred. The pH effect and desorption studies showed that ion exchange and chemisorption mechanism were involved in the adsorption process. Thermodynamic parameters such as DeltaG0, DeltaH0 and DeltaS0 for the adsorption were evaluated. Effect of foreign ions on adsorption of molybdate has been examined. The results showed that ZnCl2 activated coir pith carbon was effective for the removal and recovery of molybdate from water.     

Enhanced ethanol production through selective adsorption in bacterial fermentation

To alleviate the ethanol inhibition of Escherichia coli KO11 (ATCC 55124), during fermentation, online ethanol sequestration was achieved using F-600 activated carbon. Two separate schemes were tested, one involving direct addition of activated carbon to the fermentation flask for the purpose of in-situ adsorption and a second involving an externally located activated carbon packed bed. For the in-situ ethanol adsorption experiments, varying amounts of adsorbent were added to the medium at the start of the fermentation. The addition of the activated carbon in the fermentation broth resulted in increased glucose utilization and ethanol production for all flasks containing activated carbon. For the control flasks, approximately 75% of the available substrate was utilized before the fermentation was inhibited. The entire glucose supply of flasks containing activated carbon was depleted. Ethanol production was also increased from 28 g/L for the control containing no activated carbon to nearly 45 g/L (including the ethanol in the adsorbed phase) for the flasks containing activated carbon. The implementation of an externally located packed bed adsorber for the purpose of on-line ethanol removal was tested over a number of adsorption cycles to evaluate the performance of the adsorption bed and the ethanol productivity. Results indicate that maintaining ethanol fermentation medium concentrations below 20 ∼ 30 g/L extends and enhances ethanol productivity. After 3 cycles over a period of 180 h, an additional 80% ethanol was produced when compared to the control experiments, despite the suboptimal acidic pH of the medium.     

Biosorption and Reuse Potential of a Blue Green Alga for the Removal of Hazardous Reactive Dyes from Aqueous Solutions

The adsorption potential of a nonliving alga Nostoc comminutum for the removal of hazardous dyes from aqueous solutions was assessed. The algal biomass in its native form exhibited the highest dye removal efficiency at a pH of 1 and at a contact time of 50 min. The effect of various chemical pretreatments was studied in order to assess the role of surface chemistry and the underlying mechanism. Combined with Fourier transform infrared (FTIR) studies, it was concluded that the carboxylic and amine groups played a dominant role in the dye binding process. pH studies further revealed that besides the electrostatic mechanism, other physical interactions might be operative, which is also revealed from the Dubinin-Radushkevich (D-R) isotherm model. Kinetic studies indicated that the adsorption process followed the second-order kinetics and particle diffusion mechanisms were operative. Thermodynamic studies revealed that the adsorption of two dyes onto the algal biomass was feasible, spontaneous, and exothermic under the studied conditions. Microwave irradiation was proposed as a green method for the regeneration and reuse of the biomass. A 16% loss in the regeneration efficiency of the biosorbent was observed, which reveals its stability and reuse potential. Column experiments with real textile wastewater established the practicality of the developed system. Finally, a comparative study revealed the efficacy of the biosorbent with other previously reported biosorbents for dye removal.     

Use of a microbial sensor: inhibition effect of azo-reactive dyes on activated sludge

This paper summarizes the methodology utilized for measuring the toxic and inhibitory effects of azo-reactive dyes on the activity of activated sludge. The microbial sensor employed in this study consisted of a small-fluidized bed reactor in which the microbial mass was immobilized on spherical (diameter =1-2 mm) reticulated sinter glass carriers. To sustain a highly dense population of aerobic microbes, pure oxygen was supplied via a cylindrical chamber, which comprised part of the sample re-circulation system. The mean hydraulic retention time in the microbial sensor ranged between 30 and 40 min, while temperature was maintained at 30 degrees C and pH at 6.4. Inhibition of microbial activity (toxicity) was determined as the mean percent reduction in carbon dioxide production from microorganisms' respiration. Several azo-reactive dyes demonstrated toxicity when applied at a high concentration (2 g/l), however, a portion of the microbes showed tolerance to the dyes. Moreover, textile wastewater demonstrated very efficient biodegradation.     

Dye adsorption by sewage sludge-based activated carbons in batch and fixed-bed systems

The present research work deals with the production of activated carbons by chemical activation and pyrolysis of sewage sludges. The adsorbent properties of these sewage sludges based activated carbons were studied by liquid-phase adsorption tests. Dyes removal from colored wastewater being a possible application for sludge based adsorbents, methylene blue and saphranine removing from solution was studied. Pure and binary adsorption assays were performed in batch and fixed bed systems. In all cases studied, the adsorbents produced from sewage sludges were able to adsorb both the compounds considered here. Nevertheless, time required for reaching equilibrium, adsorptive capacity and fixed bed characteristic parameters were different for these two compounds. Methylene blue adsorption occurred faster than that of saphranine, and it was preferably adsorbed when treating binary solutions. It could be concluded that the sewage sludge-based activated carbons may be promising for dyes removal from aqueous streams.     

Application of biological activated carbon as a low pH biofilter medium for gas mixture treatment

Packing material is a crucial component of a bioreactor as it is the microbial population's habitat. This study assessed potential improvements to current biofiltration processes by investigating use of a novel support medium. Biological activated carbon (BAC) with microorganisms growing on granular activated carbon can produce a novel medium in which both adsorption and biodegradation contribute to pollutants removal. Investigation of carbon characteristics demonstrated that BAC was an ideal packing medium for biofiltration. The application of the novel packing medium for gas mixture treatment was evaluated in a low pH biofilter. Results demonstrated that BAC biofilter obtained high removal efficiency for both H(2)S and toluene. The removal mechanisms of BAC were investigated after the biofilter operation and it demonstrated that the performance of the BAC system was mainly controlled by the additive contributions of two removal mechanisms - adsorption and biodegradation. This study also indicated the potential for simultaneous treatment of hydrogen sulfide and toluene at low pH condition.     

Mechanistic studies on the binding of Acid Yellow 99 on coir pith

The interaction of Acid Yellow 99 (AY 99) with coir pith has been investigated in aqueous medium to understand the mechanism of adsorption and explore the potentiality of this biomass towards controlling pollution resulting from textile dyes. The obtained results establish that one gram of coir pith can adsorb 442.13 mg of AY 99. The adsorption process is found to be a function of pH of the solution, the optimum pH value being 2.0. The process follows Langmuir-Freundlich dual isotherm model. Scanning electron microscopic analysis demonstrates that on dye adsorption the biomass develops uneven and irregular surface. X-ray diffraction study indicates incorporation of the dye into the micropores and macropores of the adsorbent and thereby enhancing its degree of crystallinity. The results of Fourier transform infrared (FTIR) spectroscopy and chemical modification of the functional groups establish that binding of AY 99 on coir pith occurs through electrostatic and complexation reaction.     

Dye removal from aqueous solution by adsorption on treated sawdust

Formaldehyde treated and sulphuric acid treated saw dusts were used to adsorb malachite green at varying dye concentration, adsorbent dose, pH and agitation time. Similar experiments were conducted with laboratory grade activated carbon to compare the results. The adsorption efficiency of sulphuric acid treated sawdust (SD) was higher than formaldehyde treated SD. The adsorption followed first order rate expression and Lagergren equation. An initial pH in the range of 6-9 was favorable for the dye removal by both the adsorbents. Dilute solutions were effectively decolorized by the adsorbents. It is proposed that in batch or stirred tank reactors, both adsorbents can be an attractive option for dye adsorption.     

Continuous adsorption and recovery of Cr(VI) in different types of reactors

This study reports the results of experiments on continuous adsorption and desorption of Cr(VI) ions by a chemically modified and polysulfone-immobilized biomass of the fungus Rhizopus nigricans. A fixed quantity of polymer-entrapped biomass beads corresponding to 2 g of dry biomass powder was employed in packed bed, fluidized bed, and stirred tank reactor for monitoring the continuous removal and recovery of Cr(VI) ions from aqueous solution and synthetic chrome plating effluent. Parameters such as flow rate (5, 10 and 15 mL/min), inlet concentration of Cr(VI) ions (50, 100, 150 and 250 mg/L) and the depth of biosorbent packing (22.8, 11.2 and 4.9 cm) were evaluated for the packed bed reactor. The breakthrough time and the adsorption rates in the packed bed column were found to decrease with increasing flow rate and higher Cr inlet concentrations and to increase with higher depths of sorbent packing. To have a comparative analysis of Cr adsorption efficiency in different types of reactors, the fluidized bed reactor and stirred tank reactor were operated using the same quantities of biosorbent material. For the fluidized bed reactor, Cr(VI) solution of 100 mg/L was pumped at 5 mL/min and fluidized by compressed air at a flow rate of 0.5 kg/cm.(2) The stirred tank reactor had a working volume of 200 mL capacity and the inlet/outlet flow rate was 5 mL/min. The maximum removal efficiency (mg Cr/g biomass) was obtained for the stirred tank reactor (159.26), followed by the fluidized reactor (153.04) and packed bed reactor (123.33). In comparison to the adsorption rate from pure chromate solution, approximately 16% reduction was monitored for synthetic chrome plating effluent in the packed bed. Continuous desorption of bound Cr ions from the reactors was effective with 0.01 N Na(2)CO(3) and nearly 80-94% recoveries have been obtained for all the reactors.     

Adsorption of chromium from aqueous solution on treated sawdust

The adsorption of Cr(VI) from aqueous solutions on formaldehyde treated sawdust (SD) and sulphuric acid treated sawdust carbon (SDC) of Indian Rosewood, a timber industry waste, was studied at varying Cr(VI) concentrations, adsorbent dose, pH and agitation time. Similar experiments were conducted with commercially available coconut based activated carbon to compare the results. The Cr(VI) adsorption efficiency on SDC was higher than SD. The adsorption followed first order rate expression and Lagergren equation. An initial pH of 3.0 was most favorable for Cr(VI) removal by both the adsorbents. Maximum Cr(VI) was sequestered from the solution within 60 min after the beginning for every experiment. It is proposed that SDC and SD can be potential adsorbents for Cr(VI) removal from dilute solutions.     

Significance of exploiting non-living biomaterials for the biosorption of wastewater pollutants

Industrial effluents from various sectors have become a matter of major environmental concern. The treatment of wastewater in recent year plays a significant role in order to remove the pollutants and to safeguard the water resource. The conventional wastewater treatment is considered costlier and associated with problem of sludge generation. Biosorption methods are considered as the potential solution due to their economical efficiency, good adsorption capacity and eco-friendliness. In this review, an extensive list of biosorbents from algae, bacteria, fungi and agricultural byproducts have been compiled. The suitability of biosorbents towards the eradication of heavy metals, textile dyes and phenolic compounds were highlighted. It is evident from the literature survey of recently published research articles that the biosorbents have demonstrated outstanding removal potential towards the wastewater pollutants. Therefore, biosorbents from the source of dead microbial and agricultural byproduct can be viable alternatives to activated carbon for the wastewater treatment.     

Activated carbons from waste biomass by sulfuric acid activation and their use on methylene blue adsorption

Preparation of the activated carbons from sunflower oil cake by sulphuric acid activation with different impregnation ratios was carried out. Laboratory prepared activated carbons were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon was determined. The effects of various process parameters i.e., temperature, pH, initial methylene blue concentration, contact time on the adsorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption onto the activated carbons were studied. Langmuir isotherm showed better fit than Freundlich isotherm for all activated carbon samples. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The separation factor (R(L)) revealed the favorable nature of the isotherm of the MB activated carbon system.     

以纸为碳源去除地下水硝酸盐的研究

研究了以纸为碳源和反应介质的生物反应器对水中硝酸盐的去除。结果表明,以纸为碳源的反应器启动快．反硝化反应受温度及水力停留时间影响大。25℃的反硝化速率是14℃的1．7倍。在室温25±1℃,进水硝酸盐氮浓度为45．2mg·L^-1、水力停留时间8．6h时,反应器对硝酸盐氮的去除率在99．6％以上,当水力停留时间为7．2h,氮去除率只有50％。反硝化反应受pH值和溶解氧的影响小,反应进行过程中,纸表面形成了生物膜,纸也被消耗了．采用反应器出水再经活性炭吸附的工艺流程处理高硝酸盐氮地下水,<33．9mg·L^-1的硝酸盐氮完全去除,没有出现NC2-N,最终出水水质DOC<11mg·L^-1。     

An integrated process of textile dye removal and hydrogen evolution using cyanobacterium,Phormidium valderianum

The work deals with the removal of textile dyes from wastewater using cyanobacteria and integrating the dye removal ability of the organism with the ability to produce hydrogen. Phormidium valderianum, a marine cyanobacterium, has been shown to remove more than 90% of textile dyes Acid red, Acid red 119 and Direct black 155 from the solutions in the pH range higher than 11. Presence of phenolic compounds and metal chelators drastically reduced the dye adsorption capacity of the organisms. The mechanism involved in the dye adsorption has been investigated. Hydrogen production by cells grown in presence of dyes in any phase of their growth was found to be less in comparison to that of control (grown without dye). A laboratory scale reactor was designed to integrate the hydrogen production and dye removal ability of P. valderianum.