Department of Chemical Engineering
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Item Biofiltration: Essentials, Research and Applications(Wiley, 2012-03) Raghuvanshi, Smita; Gupta, SureshItem Biodegradation kinetics of Cr (VI) by acclimated mixed culture(JCE, 2011-05) Raghuvanshi, Smita; Gupta, SureshChromium was discovered in 1797 by Vauquelin. Numerous industrial applications raised chromium to a very important economic element. At the same time, with the development of its uses, the adverse effects of chromium compounds in human health were being investigated. Both acute and chronic toxicity of chromium are mainly caused by hexavalent compounds. It is highly toxic in nature and causes adverse effects on human beings. The present study deals with the removal of hexavalent chromium compound from industrial waste water using biodegradation by an acclimated mixed culture developed from activated sludge. The biodegradation studies are conducted for an initial Cr(VI) concentration ranging from 10-50 mg/L. The enrichment of culture is carried out for a period of 7 days. In these experiments, 100 mL of minimum salt medium (MSM) is autoclaved and added with known amount of acclimated mixed culture obtained from the enrichment procedure. Known amount of Cr(VI) is added in autoclaved MSM to maintain the required concentration of Cr(VI). The flasks are kept in the rotary shaker which is maintained at 37 C and at 150 rpm throughout the biodegradation process. The samples are collected at different intervals. The obtained biomass growth is significant and indicate the considerable decrease in Cr(VI) concentration in the solution The biodegradation rate kinetic parameters are obtained for zero order and three and half order kinetic models.Item Kinetic and Equilibrium Studies of Cr (VI) Removal from Aqueous Solutions using Activated Neem Bark(WRA, 2011-06) Gupta, SureshHexavalent chromium [Cr(VI)] has a dominant presence in most of the effluent streams as compared to other heavy metal ions coming out from the different industries such as metal finishing, tannery, electroplating, etc. Due to its carcinogenic and toxic nature, it is considered as one of the most important environmental problems. The solution for this problem is a cost effective and eco-friendly treatment technique. Various treatment techniques such as chemical precipitation, ion exchange, membrane separation, electro-coagulation and chemical reduction are available to reduce the contamination of Cr(VI) in the effluent streams. These techniques are not eco-friendly and economically viable for the large volume of wastewater treatment. Adsorption using low cost adsorbents is found to be one of the cost effective technique for Cr(VI) removal from the effluent streams. In the present study, a waste biodegradable material, neem bark, is used. This neem bark is activated using concentrated sulphuric acid (98 wt%) and is used as an adsorbent for Cr(VI) removal from aqueous solutions. Batch adsorption experiments were conducted for determining the performance of activated neem bark for removal of Cr(VI). The effect of various important parameters such as effect of contact time, initial Cr(VI) concentration and dosage of adsorbent for the removal of Cr(VI) using activated neem bark adsorbent are studied. The kinetic studies show 70% removal of Cr(VI) using activated neem bark as an adsorbent while keeping 100 mg/L of initial Cr(VI) concentration. The equilibrium data for the adsorption of Cr(VI) on activated neem bark is being tested with Langmuir isotherm model and Freundlich isotherm model. It is observed that it is following the Langmuir isotherm model and the corresponding adsorption capacity of activated neem bark is 26.95 mg/g. Pseudo first-order and second-order rate kinetic models are used to evaluate the mechanism of adsorption of Cr(VI) on activated neem bark. It is observed that the adsorption of Cr(VI) on activated neem bark follows second order kinetics.Item Modeling and simulation of isothermal fixed-bed adsorption column: comparison of pore and solid diffusion mass transfer( Nova Science Publishers, 2011) Gupta, SureshA study of comparative analysis of two intra-particle mechanisms, pore diffusion and solid diffusion, is explained to understand the dynamics of fixed-bed adsorber column. A mathematical model is developed to account for the axial dispersion and both the external and internal mass-transfer resistances in the adsorption of solute. The developed mathematical models of pore diffusion and solid diffusion are solved numerically using the Explicit Finite Difference Technique and the simulations are carried out to obtain the breakthrough curves at different operating conditions. The proposed models are validated with the experimental results reported in the literature. The proposed model with solid diffusion intraparticle mechanism (s.d. = 0.0285) shows a good agreement with the experimental results as compared to the model reported by Vázquez et al. (2006) (s.d. = 0.0542). It is found that the breakpoint time is delayed for solid diffusion compared to pore diffusion under similar conditions. Also the steepness of the breakthrough curve is more for solid diffusion than pore diffusion mechanism. It is also observed that the percentage removal of the solute is more and the unused bed length is less for solid diffusion model which indicates the proper utilization of the bed. To have better understanding of the dynamic behavior of adsorber column, other important and influencing parameters such as flow rate, bed length, particle radius, and external film mass transfer coefficient, are varied and their effect on the breakthrough curve using pore diffusion and solid diffusion models are studied. The other important parameters such as the total amount of solute adsorbed (q^sub t^), the amount of solute sent to the bed (m^sub t^), equilibrium uptake of the bed (q^sub eq^), empty bed residence time (EBRT), percentage removal of solute (S), the adsorbent exhaustion rate (R^sub a^), and the fraction of unused bed length (y) are calculated for better understanding of the adsorption mechanism.Item Nano-adsorbents for wastewater treatment: A review(WRA, 2011-06) Gupta, SureshThe concern over increasing awareness for development of systems to improve water quality for effluents from wastewater treatment and industrial facilities has provided incentives to develop new - technologies and improve performance of existing technologies. Various methods exist for the removal of toxic metal ions from aqueous solutions, but adsorption is by far the most versatile and widely used process. In recent years, a great deal of at tent ions hai been focused onto the application of nunostructured materials as adsorbents or catalysts to remove toxic and harmful substances from wastewater and air. This study mainly focused on those nano-adsorbents which are used for wastewater treatment. The nano-adsorbents which were studied are classified into two classes namely carbon derived (inform of tubes, wires and particles) and non carbon derived (metals, metal oxides, etc.) nano-adsorbents. A detailed study on each nano-adsorbent is done through studying their synthesis, characterization, adsorption characteristics and their uses and application in the real world. The synthesis of nano-adsorbents was studied using different methods such as arc discharge method, laser ablation and chemical vapour deposition. The characterization of nano-adsorbents was carried out using Raman spectroscopy. The experimental characteristics of adsorption at different pH, temperature are studied and their results are discussed. The applications of nanomaterials may yield benefits to the environment through the development of new technologies and the widespread uses of nanomaterials will also likely result in their introduction to our environment. It is therefore critical that the researchers in the area of nanotechnology should address important aspects related to the development of nano-materials. The present study also deals with the future developments of nano-materials and challenges in this field of environmental engineering.Item Experimental, kinetic, equilibrium and regeneration studies for adsorption of Cr(VI) from aqueous solutions using low cost adsorbent (activated flyash)(Taylor & Francis, 2012-08-03) Gupta, SureshIn the present study, activated flyash — a low-cost adsorbent, is used as for Cr(VI) removal from aqueous solutions. Flyash is activated by giving heat treatment and with the use of concentrated sulfuric acid (98% w/w). Batch adsorption experiments are carried out to investigate the effect of influencing process parameters such as initial pH, change in pH during adsorption, contact time, adsorbent amount, and initial Cr(VI) concentration. The maximum adsorption of Cr(VI) on activated flyash is found at an initial pH value of 1. The value of pH increases with increase in adsorption of Cr(VI). The equilibrium data for adsorption of Cr(VI) on activated flyash is tested with different adsorption isotherm models such as Langmuir, Freundlich, Redlich—Peterson, Koble—Corrigan, Tempkin, Dubinin—Radushkevich and generalized isotherm models. The Koble—Corrigon isotherm model is found to be the most suitable one for Cr(VI) adsorption using activated flyash. The maximum adsorption capacity obtained is 21.9 mg g−1 at a pH value of 1. The adsorption process follows the second order kinetics and the corresponding rate constants are obtained at different initial Cr(VI) concentrations. Desorption of Cr(VI) from activated flyash using acid and base treatment shows a higher desorption efficiency by more than 85%. A feasible methodic solution for the disposal of contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during the desorption process is proposed.Item Experimental Investigations and Theoretical Modeling Aspects in Column Studies for Removal of Cr(VI) from Aqueous Solutions Using Activated Tamarind Seeds(Scientific Research, 2010) Gupta, SureshContinuous adsorption experiments are conducted using fixed-bed adsorption column to evaluate the performance of the adsorbent developed (from activated tamarind seeds) for the removal of Cr(VI) from aqueous solutions and the results obtained are validated with a model developed in this study. The effects of significant parameters such as flow rate, mass of adsorbent, and initial Cr(VI) concentration are studied and breakthrough curves are obtained. As the flow rate increases from 10 to 20 mL min-1, the breakthrough time decreases from 210 to 80 min. As the mass of adsorbent increases, breakthrough time gets delayed. The breakthrough times are obtained as 110, 115 and 210 min for 15, 20 and 25 g of activated tamarind seeds. As the initial Cr(VI) concentration increases from 100 to 200 mgL-1, the break point time decreases from 210 to 45 min. The process parameters for fixed-bed adsorption such as breakthrough time, total percentage removal of Cr(VI), adsorption exhaustion rate and fraction of unused bed length are calculated and the performance of fixed-bed adsorption column is analyzed. The mechanism for Cr(VI) adsorption on activated tamarind seeds is proposed. At low value of solution pH (= 1), the increase in Cr(VI) adsorption is due to the electrostatic attraction between positively charged groups of activated tamarind seeds and the HCrO4-. A mathematical model for fixed-bed adsorption column is proposed by incorporating the effect of velocity variation along the bed length in the existing model. Pore and surface diffusion models are used to describe the intra-particle mechanism for Cr(VI) adsorption. The breakthrough curve obtained theoretically from pore diffusion model and surface diffusion model are compared with experimental results for different operating conditions. The standard deviation values obtained for pore diffusion model and solid diffusion model are 0.111 and 0.214 respectively.Item Modeling, simulation, and experimental validation for continuous Cr(VI) removal from aqueous solutions using sawdust as an adsorbent(Elsiever, 2009-12) Gupta, SureshContinuous adsorption experiments were performed in a fixed-bed adsorption column to evaluate the performance of low-cost adsorbent (sawdust) developed for the removal of Cr(VI) from aqueous solutions. The effects of influencing parameters such as flow rate, mass of adsorbent, initial Cr(VI) concentration were studied and the corresponding breakthrough curves were obtained. The fixed-bed adsorption process parameters such as breakthrough time, total percentage removal of Cr(VI), adsorption exhaustion rate and fraction of unused bed-length were obtained. A mathematical model for fixed-bed adsorption column was proposed by incorporating the effect of velocity variation along the bed-length in the existing model. Pore and solid diffusion models were used to describe the intra-particle mechanism for Cr(VI) adsorption. The proposed mathematical model was validated with the literature data and the experimental data obtained in the present study and the model was found to be good for explaining the behavior of breakthrough curves.Item Utilization of waste product (tamarind seeds) for the removal of Cr(VI) from aqueous solutions: Equilibrium, kinetics, and regeneration studies(Elsiever, 2009-07) Gupta, SureshIn the present study, an adsorbent was prepared from tamarind seeds and used after activation for the removal of Cr(VI) from aqueous solutions. The tamarind seeds were activated by treating them with concentrated sulfuric acid (98% w/w) at a temperature of 150 °C. The adsorption of Cr(VI) was found to be maximum at low values of initial pH in the range of 1–3. The adsorption process of Cr(VI) was tested with Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized isotherm models. Application of the Langmuir isotherm to the system yielded a maximum adsorption capacity of 29.7 mg/g at an equilibrium pH value ranging from 1.12 to 1.46. The adsorption process followed second-order kinetics and the corresponding rate constants obtained were 2.605 × 10−3, 0.818 × 10−3, 0.557 × 10−3 and 0.811 × 10−3 g/mg min−1 for 50, 200, 300 and 400 mg/L of initial Cr(VI) concentration, respectively. The regenerated activated tamarind seeds showed more than 95% Cr(VI) removal of that obtained using the fresh activated tamarind seeds. A feasible solution is proposed for the disposal of the contaminants (acid and base solutions) containing high concentrations of Cr(VI) obtained during the regeneration (desorption) process.Item Removal of toxic metal Cr(VI) from aqueous solutions using sawdust as adsorbent: Equilibrium, kinetics and regeneration studies(Elsiever, 2009-08-01) Gupta, SureshIn the present study, a low-cost adsorbent is developed from the naturally and abundantly available sawdust which is biodegradable. The removal capacity of Cr(VI) from aqueous solutions and from the synthetically prepared industrial effluent of electroplating and tannery industries is obtained. The batch experiments are carried out to investigate the effect of the significant process parameters such as initial pH, change in pH during adsorption, contact time, adsorbent amount, and the initial Cr(VI) concentration. The maximum adsorption of Cr(VI) on sawdust is obtained at an initial pH value of 1. The value of pH increases with increase in contact time and initial Cr(VI) concentration. The equilibrium data for the adsorption of Cr(VI) on sawdust is tested with various adsorption isotherm models such as Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized equation. The Langmuir isotherm model is found to be the most suitable one for the Cr(VI) adsorption using sawdust and the maximum adsorption capacity obtained is 41.5 mg g−1 at a pH value of 1. The adsorption process follows the second-order kinetics and the corresponding rate constants are obtained. Desorption of Cr(VI) from sawdust using acid and base treatment exhibited a higher desorption efficiency by more than 95%. A feasible solution is proposed, for the disposal of the contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during the desorption process. The interference of other ions which are generally present in the electroplating and tannery industrial effluent streams on the Cr(VI) removal is investigated.