Bhargav Patel

Azo calix[4]arene based neodymium(III)-selective PVC membrane sensor

We found that the PVC membrane, containing azo calix[4]arene is a suitable ionophore, exhibited a Nernstian response for neodymium (Nd(3+)) ions (with slope of 19.8±0.2 mV decade(-1) for the triply charged ion) over a wide linear range of 4.0×10(-8) to 1.0×10(-1) mol L(-1) with a detection limit 1.0×10(-8) mol L(-1), a relatively fast response time, in the whole concentration range (<10 s), and a considerable life time at least for four months in the pH range of 4.0-8.0. Furthermore, the electrode revealed high selectivity with respect to all the common alkali, alkaline earth, transition and heavy metal ions, including the members of the lanthanide family other than Nd(3+). Concerning its applications, it was effectively employed for the determination of neodymium ions in industrial waste water as well as in lake water.

Novel monohydrogenphosphate ion-selective polymeric membrane sensor based on phenyl urea substituted calix[4]arene.

A highly selective and sensitive PVC membrane, containing phenylurea substituted calix[4]arene was found to be a suitable ionophore for monohydrogen phosphate (HPO(4)(2-)) ions that exhibited a Nernstian response (with a slope of -29.4 ± 0.3 mV decade(-1)). The working concentration range of the electrode was 6.0 × 10(-8)-1.0 × 10(-1) mol L(-1) with a detection limit of 2.0 × 10(-8) mol L(-1). The response time of the sensor in the whole concentration range is very short (<8s), with a considerable lifetime of at least 15 weeks. The sensor possesses the advantages of short response time, low detection limit and a high selectivity towards a large number of inorganic anions. The developed sensor was used as an indicator electrode in potentiometric titration of monohydrogen phosphate ion with barium chloride. The proposed sensor was successfully applied for the direct determination of monohydrogen phosphate in real life samples.

Development of Leptospirillum ferriphilum dominated consortium for ferric iron regeneration and metal bioleaching under extreme stresses

Activated iron oxidizing consortium SR-BH-L enriched from Rajpardi lignite mine soil sample gave iron oxidation rate 1954 mg/L/h. Developed novel polystress resistant consortium oxidized ferrous iron under 11cP viscosity, 7.47 M ionic strength, 2.3 pH and g/L of 0.50 cadmium, 3.75 copper, 0.20 lead, 92.00 zinc, 6.4 sodium, 5.5 chloride, 154 sulphate and 393.8 TDS. The developed consortium showed 78.0% and 70.0% copper and zinc extraction from polymetallic bulk concentrate in monophasic bioleaching process. The bioregenerated ferric by the consortium in leachate showed 80.81% and 54.0% copper and zinc leaching in only 30 and 90 min. The DGGE analysis indicated the presence of 11 OTUs in the consortium. 16S rRNA gene sequence (JN797729) of the dominant band on DGGE shared >99% similarity with Leptospirillum ferriphilum. RE digestion analysis of the total 16S rRNA gene also illustrated the dominance of L. ferriphilum in the consortium.

Potentiometric Biosensing of Glucose by Fullerene-Based Silver Selective Electrodes

A novel methanofullerene containing pyridine pendants has been synthesized and used to fabricate a silver selective electrode. The selectivity coefficient was found to be 6.9 ×10−5 and 6.2 × 10−5, respectively, for Cu2+ and Hg2+, while for other cations it was less than 10−5. It has a Nernstian behavior over a wide concentration range of Ag+ ion (5 × 10−7 to 1 × 10−1 mol L−1). The slope and linear range from the calibration graph was found to be 58.8 mV decade−1 and 5.0 × 10−7 to 1.0 × 10−1 mol L−1, respectively. The limit of detection was found to be 1 × 10−7 mol L−1. The fabricated electrodes can be used in a wide pH range (pH 4–7.5) with a response time less than 10 s. The fabricated electrodes were used for bioanalysis of glucose with silver nanoparticle as the potential redox marker. The working linear range for glucose detection was found to be 1 × 10−5 to 1 × 10−3 in phosphate buffer (pH 6.6). Parameters affecting the reaction rate such as pH and the amount of GOx and AgNPs were analyzed. The lower detection limit was 1.0 × 10−6 M. The sensors exhibited very good repeatability with %R.S.D. < 6 and high sensor-to-sensor reproducibility. Application in analysis of glucose in real life sample (blood plasma) has also been demonstrated.

A novel biphasic leaching approach for the recovery of Cu and Zn from polymetallic bulk concentrate

In scale-up biphasic leaching process of polymetallic concentrate, the ferric bioregeneration cycles were performed in 15.0L down flow packed bed reactor; whereas the chemical leaching cycles were done using the biogenerated ferric in an indigenously designed 10.0L stirred tank reactor. The consortium took 25cycles for proper biofilm formation. It showed highest iron oxidation rate (IOR) of 3908.21mg/L/h at 25thcycle under no polymetallic stress. Even under stressed conditions, it was 2650-558mg/L/h. Cu extractions were 86.63-46.51 and Zn extractions were 67.89-14.74% in 1st-4thcycle, respectively. The developed consortium exhibited 17-51times higher IOR compared to original wild type consortium. Extraction isotherm for zinc with 30% Cyanex® 301 indicated that a total of two stages are required for its complete extraction using the phase ratio of 2:1 at equilibrium pH 1.5, leaving behind Fe(II) in the raffinate.

Liquid Membrane Transport Kinetics of Hg (II) by Dithio Derivatized Macrotricyclic Compound

The present study has been undertaken to investigate a process that removes inorganic mercury from waste water streams by use of a liquid membrane system in which a novel macrocyclic ligand based on dithio derivatized biscrown ether has been used as a cation carrier. The effect of temperature, stirring rate and different solvents on the kinetic parameters like k1, k2 and flux values J a max, J d max and tmax were also investigated. It was found that the membrane entrance rate constant (k1) and the membrane exit rate constant (k2) increased with increasing temperature and stirring rate. The membrane entrance rate constants (k1), exit rate constants (k2), as well as the flux values vary in the order of CH2Cl2 > CHCl3 > CCl4 in different solvents study

Biphasic Leaching Operation for the GMDC Polymetallic Bulk Concentrate

A biphasic leaching operation was employed for the extraction of copper and zinc from the GMDC polymetallic bulk concentrate (PBC). Biogenerated ferric was used in cyclic manner for fed batch metal extractions from the PBC for four cycles under the pre-optimized conditions. Zn extraction was gradually decreased with each succeeding fed-batch cycle and it resulted in 67.89, 62.46, 47.37 and 14.74% of Zn extraction in 1st, 2nd, 3rd and 4th cycle respectively. In case of copper the extraction pattern was 86.63, 81.98, 75.58 and 46.51% Cu extraction in 1st, 2nd, 3rd and 4th cycle respectively. The leachate generated in each cycle was added in 15.0 L down flow packed bed column reactor having biofilm of developed consortium SR-BH-L for the ferrous bioregeneration and the obtained maximum IOR was 2650 mg/L/h. Overall results indicated that use of bioregenerated ferric iron from the leachate yielded as high as 52.2 and 2.6 g/L Zn and Cu respectively in the solution at the end of 4th cycle. This metal concentration in the leachate is quite acceptable for economical solvent extraction process.