Chemistry

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https://hdl.handle.net/20.500.14540/125

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Phytochemical investigation of Eupatorium Odoratum L. for Cytotoxicity Antimicrobial and Antioxidant Activities
(Faculty of Chemistry, 2006) Amatya, Sajan
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Adsorptive Separation of Heavy Metals onto Xanthated Apple Waste From Aqueous Solution
(Department of Chemistry, 2006) Bashyal, Deepak
Biosorption is potentially an attractive technology for the treatment of wastewater retaining heavy metals in aqueous solution. This study investigated the feasibility of chemically modified apple waste as a novel type of biosorbent for lead, cadmium, zinc and Iron removal from aqueous medium. Xanthated apple waste as a biosorbent was prepared by simple chemical reaction with carbon disulphide under alkaline condition. The maximum exchangeable cations of the H V + -form xanthated apple waste (XAWgel) were as high as 2.52 mol/kg. The effect of pH, sorption kinetics, effect of competitive ion and isotherm were studied by batch method. The significant effect of pH was in the range of 3 to 6. Time dependency experiments for the metal ions uptake showed the biosorption rate was fast initially for 2h, followed by slow attainment of equilibrium. Sorption isotherm test showed that equilibrium sorption data were better represented by Langmuir model than the Freundlich model, and the maximum adsorption capacity of Pb(II), Cd(II), Zn(II) and Fe(III) were found to be 250, 192.30, 123.45 and 62.89 mg/g respectively. The pseudo first-order, pseudo second-order, and secondorder models were used to analyze the kinetic data. The good correlation coefficient was obtained for pseudo second-order kinetic model. XAW-gel was found to be more efficient than the conventionally used adsorbent activated carbon and other most of the biosorbent. Based on the result, a judicious choice of modification strategy for raw apple waste precursors can produce adsorbent with active xanthated surface functional groups and appears to be a promising biosorbent for removal of heavy metals from aqueous water.
Corrosion Behavior of Sputter- Deposited W-Cr-(4-15)Ni Alloys in Nacl and Naoh Solutions
(Central Department of Chemistry, 2008) Kharel, Pom Lal
The synergistic effect of chromium addition in the sputter-deposited amorphous or nanocrystalline W-Cr-(4-15)Ni alloys is studied in 0.5 M NaCl and alkaline NaOH solutions at 25oC, open to air using immersion tests and electrochemical measurements. In 0.5 M NaCl solution, the addition of chromium to W-Cr-(4-15)Ni alloys containing 42-75 at % chromium increases the corrosion resistance and makes the open circuit potential more noble so as to show higher corrosion resistance than those of alloy-constituting elements (that is, tungsten, chromium and nickel). The corrosion rates of all the examined W-Cr-(4-15)Ni alloys are almost same (that is, about 2-3 x 10-3 mm/y) and are about one order of magnitude lower than that of tungsten and even lower than that of chromium metal after prolonged immersion in 0.5 M NaCl solution. In 1 M NaOH solution, the corrosion rates of the W-Cr-(4-15)Ni alloys (about 2-5 x 10-3 mm/y) are about two orders of magnitude lower than that of tungsten and nearly one order of magnitude lower than that of chromium metal. The open circuit potential of the W-Cr-(4-15)Ni alloys is generally increased with increasing chromium content in different concentrations of NaOH solutions. The open circuit potentials of all the examined W-Cr-(4-15)Ni alloys are in more noble direction in 0.5 M NaCl solution than that in 1 M NaOH solution. The passivity of the W-Cr-(4-15)Ni alloys is increased with decreasing the concentration of NaOH solutions at 25oC.
an inexpensive method of determination of fluoride
(faculty of science, 2009) Adhikari, Upendra
An inexpensive spectrophotometric method of determination of fluoride inwater is developed which is based on bleaching action of fluoride ions on thecoloured complex of Fe (III) with salicylic acid to form stable, colourlesshexafluoride complex of iron. The conditions of the method (pH, stabilityand combination ratio) were studied and a standard curve was obtained for0-20 mg F - /L at 525nm. A study was conducted on interference withcomplexing cations that react with fluoride ions and anions that react withFe (III) to give more stable complex than Fe (III)-fluoride complex. Theresults obtained from this method are compared with standard SPADNS-Zirconyl chloride method. The results obtained are in good agreement withSPADNS-Zirconyl chloride method of determination of fluoride. Thecalibration sensitivity of the method is found to be 0.042 μg -1 .Thedetection limit is found to be 1.1μg mL -1 at 98.3% confidence level. Thesandell’s sensitivity of the method is found to be 0.02 μg mL -1 mL cm cm -2 . -1
Adsorption Behaviour of Chromium(Vi) onto Surface Modified Sugarcane Waste
(Department of Chemistry, 2009) Wagle, Deepak
An effective chemically modified adsorbent based on sugarcane wastehas been prepared by treating with concentrated sulphuric acid in 2:1weight:volume ratio. Thus prepared adsorbent has been found to be effective in theadsorption of chromium from aqueous medium. The efficacy of the adsorbentin the removal of chromium was evaluated by batch adsorption method. Theeffect of initial concentration, contact time and pH of the solution wasinvestigated. The maximum adsorption capacity onto this adsorbent wasfound to be 195 mg/g at their optimal pH 1 at which unmodified bagasse hasonly 58 mg/g. The characterization of adsorbent was done by determiningsurface area and Boehm’s titration method. Freundlich isotherm and pseudo-second order kinetic model gave better explanation of the adsorption process.
Optimization of Xanthation And It’s Application For Al(III) And Fe(III) Removal Onto Apple Waste
(Department of Chemistry, 2009) Nepal, Binod
Novel xanthated apple waste derivative were prepared by chemical modification of apple waste using carbon disulphide (CS2) under different alkaline condition i.e. 5%, 10%, 15% and 20% NaOH concentration. The optimization of NaOH concentration in the xanthation process was evaluated by the adsorption of Fe3+ ions and subsequently by the evaluation of the total exchangeable protons by titration method. The total exchangeable protons were found to be 3, 4, 6 and 6 mole/kg for four types of xanthated apple waste (XAW), xanthated at 5%, 10%, 15% and 20% NaOH concentration, respectively. Similarly, the maximum absorption capacity (qmax) value for the adsorption of Fe(III) were found to be 73.5, 105.26, 196.07 and 196.07 mg/g on four types of XAW xanthated at 5%, 10%, 15% and 20% NaOH concentration, respectively. The experimental results showed that the optimal condition of NaOH concentration for the xanthation of apple waste was 15%. The qmax value for the adsorption of Al(III) onto the optimized XAW at optimum pH 4 was found to be 181.81 mg/gm. Kinetics and isotherm studies revealed that for both metals Langmuir isotherm fitted well and adsorption mainly followed pseudo-second order kinetics.
Adsorption of Arsenic(III) Using Iron(III)-Loaded Modified Sugarcane Begasse
(Department of Chemistry, 2009) Aacharya, Sabita
Arsenic is a toxic element and may be found in natural water as well as industrial wastes. Leaching of As from industrial wastes into ground water may cause significant contamination which requires proper treatment before its use as a drinking water. The chemistry of As and its natural occurrence in some water resources combine to create a potent, widespread human health risk, requiring management and removal from drinking water. The present study describes the removal of As(III) from water. Of the available conventional techniques, adsorption is the most versatile and effective separation technique and utilizes agricultural and natural waste as adsorbent. The study mainly focuses on the removal of As(III) on Fe(III) loaded modified Sugarcane begasse in batch studies as a function of pH, dosage of adsorbent and contact time. Kinetics revealed that the uptake of As(III) ion by rapid and equilibrium time was independent of initial As(III) concentration and the adsorption process followed a pseudo second-order kinetics equation. The As(III) was strongly dependent on pH and dosage of adsorbent. The adsorption isotherm best fit the Langmuir equation as compared to Freundlich.
Adsorption of Cd (II) From Aqueous Solution by Activated Charcoal Derived from Lapsi Seeds
(Department of Chemistry, 2009) Lamsal, Nirma
The potential and effectiveness of activated carbon derived from carbonization of Lapsi (Choerospondias axillaris) seed for adsorptive removal of cadmium (II) was examined by adsorption technique. The carbon obtained from Lapsi seed was chemically modified by treating with 1:1 HNO3 at 60o C. Boehm method was used to estimate the oxygen containing acidic functional groups. The acidic functional group, specific surface area and adsorptive capacity all greatly increased with chemical treatment with nitric acid. The specific surface area of the charcoal, after chemical treatment, increased to 600 m2/g from 45 m2/g. The ash, moisture and carbon contained in modified charcoal were found to be 3.5%, 0.2 % and 96.3 % respectively. The performance of the adsorbent was in par with commercial activated charcoal. Various parameters such as contact time, adsorbent dose, pH and metal ion concentrations on adsorption were studied, optimized and applied in the present study. The maximum adsorption capacity of charcoal to adsorb Cd(II) was found to be 12.53 mg/g at optimum pH of 6 and equilibrium was attained within 150 minutes. The adsorption of cadmium followed pseudo second order kinetic model and the rate constant of the process was found to be 1.73x10-3 g mg-1 min-1. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich isotherm.
Radiochemical Study of Marble and Granite Fromlocal Market
(Department of Chemistry, 2010) Thapa, Birendra
A sensitive method is used for the extraction and determination of soluble uranium in marble and granite using Isobutyl Methyl Ketone (IBMK) as extractant and 0.02%(w/v) Arsenazo (III) as a chromogenicre agent. The present study assesses the gross radioactivity and extractable uranium in marble and granite samples. A Multichannel Analyzer (MCA)coupled with NaI (Tl) crystal detector was used for the measurement of gross radioactivity where as spectrophotometer was used to estimate the uranium contained in sample with the help of Arsenazo (III). The extraction involved the adjustment of pH at 0.9.The efficient extraction was achieved by the addition of at least 10 gms of Al (NO . This method involved the reduction of UO 2 (+2) to U (IV) by using granulated Zinc in concentrated hydrochloric acid. The physical measurements showed the presence ofgross radioactivityinthe range266.19 Bq/kg to 644.268 Bq/Kg in marble and 871.63 Bq/kg to 1127.32 Bq/Kg in granite while the chemical analysis showed the marble sample analyzed had the uranium concentration in the range of 0.02 ppm to 0.06 ppm and the granite sample had the range of 0.08 ppm to 0.12 ppm. Key Words: Arsenazo (III),IBMK,Multichannel Analyzer,Spectrophotometer, Uranium.
Adsorptive Removal of Fe (II) From Aqueous Solution by Functionalized Sugarcane Bagasse
(Department of Chemistry, 2010) Acharya, Mahendra
In the present study, adsorption of Fe(II) onto different biosorbents prepared from sugarcane bagasse, i.e, raw sugarcane bagasse, charred sugarcane bagasse and phosphoric acid modified charred sugarcane bagasse has been studied by batch equilibration method under different experimental conditions. Effects of pH, Fe(II) concentration, and contact time on the adsorption of divalent iron ion were investigated. The concentration of Fe(II) ion in the test solution was determined spectrophotometrically. Maximum adsorption was observed at pH 2.5 for all the adsorbents at the optimum contact time of 9 hour, 7 hour, and 4 hour respectively for RSB, CSB and PCSB. Maximum adsorption capacity (qmax) value for the RSB, CSB and PCSB was found to be 50.5, 111.4 and 175 mg/g respectively. Adsorption of the Fe(II) ion on all the adsorbents followed Langmuir isotherm more strictly than Freundlich isotherm. The results shows that studied adsorbents may be attractive low cost alternative for the treatment of wastewater in lower concentration of iron.
Corrosion behavior of sputter-deposited W-Mo alloys in NaOH solutions
(Department of Chemistry, 2010) Khadka, Arun
The corrosion behavior of the sputter-deposited nanocrystalline WMo alloys is studied after immersion for 24-29 h in different concentrations of NaOH solutions at 25 o C, open to air by using corrosion tests and open circuit potential measurements. Molybdenum metal acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited W-Mo alloys so as to show the lower corrosion rates than those of alloyconstituting elements (that is, tungsten and molybdenum) after immersion for 24-29 h in NaOH solutions. In general, the open circuit potentials of all the examined W-Mo alloys are shifted to the more positive (noble) direction with increasing the molybdenum content in the alloys. The stability of the spontaneous passive films of the binary W-Mo alloys is decreased with increasing the concentrations of NaOH solutions. However, the corrosion rates of all the examined W-Mo alloys are almost independent of concentrations of NaOH solutions (that is, 0.01 M, 0.1 M and 1 M NaOH).
Biological and Phytochemical Studies on Heartwood of Acacia catechu of Nepal
(Department of Chemistry, 2011) Subedi, Yagya Prasad
Biological and Phytochemical screening of heartwood of Acacia catechu was studied. Phytocostituents found were Sterols, Flavones Aglycones, Tannins and Polyphenols. The column chromatography of diethyl ether fractions result in the isolation of β-Sitosterol (Ac1), Quercetin (Ac4), (+) Catechin (Ac6). Other four compounds Ac2, Ac3, Ac5, Ac7 whose work is on progress, were also isolated. Antibacterial screening, antifungal screening and brine shrimp bioassay of different fractions showed that hexane, chloroform, diethyl ether, ethyl acetate and methanol fraction were biologically active. In brine shrimp bioassay only diethyl ether, ethyl acetate, and methanol fraction showed activity.
Preparation and studies of ratiometric fluorescent chemosenors based on the attenuation of excitation energy transfer
(2011) Acharya, Jiba Raj; Evgueni E. Nesterov
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Effect of cationson the corrosion behaviour of galvanized steel sheet of Nepal in wet-dry cyclic condition
(2011) Yadav, Neelima; Amar Prasad Yadav
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Effect of Cerium Ions on the Corrosion of Galvanised Steel in 0.5 M Na 2 SO 3 Solution
(Department of Chemistry, 2012) Neupane, Dharmendra
Chromate conversion coatings have been widely used in industry for a long time to improve the corrosion resistance galvanized steels. Hexavalent chromium, however, has high toxicity and carcinogenesis. Therefore, alternative and more environmentally friendly surface treatments need to be developed. Rare earth metal ions, such as cerium, is recognized as an effective corrosion inhibitor and environmentally friendly. In present study effects of Ce (III) and Ce (IV) ions on the corrosion behaviour of galvanised steel have been studied in 0.5 M Na 2 SO 3 solution. A composite coating of cerium and zinc has been prepared by pulse deposition technique and its effect on the inhibition of corrosion of galvanized steel has been evaluated in terms of E iv corr , Icorr and Tafel constants. It was found that the composite coating decreased the corrosion rate by more than 50 times. On the other hand, Ce (IV) ion was found to increase the corrosion rate due to taking part in cathodic reaction.
Synthesis and Evaluation of Barbituric Acid Derivatives as Protein Tyrosine Phosphatase 1B Inhibitors
(Faculty of Chemistry, 2012) Khadka, Deegendra
Rapid increase of obesity and diabetes in modern society increases the risk of other complications, such as cardiovascular diseases, blindness, renal failure and even cancer. Orlistat is the only drug approved currently by the US Food and Drug Administration (FDA) for the treatment of obesity. Other drugs previously approved were suspended due to side effects. Sulfonylureas, thiazolidinediones, and meglitinides are available in the market as the drugs for type 2 diabetes mellitus but they are not kept a distance from side effects. Science communities have been focusing attention on the development of novel drugs that are safer and more efficient in treating obesity and diabetes. Protein tyrosine phosphatase1B (PTP1B) is an enzyme closely related with these diseases. PTP1B is a negative regulator of leptin and insulin signaling pathways. Genetic deletion of PTP1B in mice improved both leptin and insulin signaling, resulting in the resistance to diet-induced obesity and the enhancement of insulin sensitivity and glucose tolerance. The enhancement of leptin signaling reduced food intake and increased energy expenditure, resulting in weight loss in mammals. Increased PTP1B expression has also been observed in insulin-resistant states associated with obesity. These results established PTP1B as a target for the treatment of both obesity and type 2 diabetes. The aim of this research is to develop low molecular weight inhibitors of PTP1B which have a good inhibitory potency, selectivity and favorable pharmacokinetics for the development of antidiabetic and antiobesity drugs. Barbituric acid was selected as a scaffold for the derivatization. A series of derivatives containing a single substitutuent were synthesized and their efficacy to inhibit PTP1B activity was determined. The most potent compound II-5e showed IC 50 of 11 µM against PTP1B and 27 µM against VHR. The nature of inhibition by compound II-5e was investigated by steady-state kinetic experiments with PTP1B, VHR and YPTP1. When the mode of inhibition was examined by the Lineweaver-Burk plot analysis of the kinetic experiments, II-5e inhibited PTP1B and YPTP1 noncompetitively and VHR competitively.
Sorption of As (III) and As (V) onto Dalbergia sissoo & Arundodonax Sawdust
(Department of Chemistry, 2012) Bhattarai, Pushpa
The application of low-cost, ecofriendly bioadsorbents as an alternate to the conventional methods of removing As (III)and As (V) ions from aqueous media has been investigated. Present study deals with the adsorption of As (III)and As (V) from aqueoussolution onto chemically modified form of saw dusts.The Chemically modified Dalbergiasissoo sawdust and Arundo donax sawdust were obtained by performing phosphorylation followed by treatment with iron (III) solution in aqueous media. Batch studies were performed at an initial concentration of 1mg/l to evaluate the influence of various parameters such as pH, equilibrium time, amount of adsorbent and concentration of adsorbate. Studies showed that pH of aqueous solution drasticall yaffected As (III)and As (V)adsorptionas a result the removal efficiency altered with the change in initial pH of the solution. The maximum efficiency for the iron (III)-loaded phosphorylated Dalbergia sissoo sawdust [FePDSD]andiron (III)-loaded phosphorylated Arundo donax sawdust [FePASD]were achieved at pH 9, &7 for As (III) and at pH 3, & 5 for As (V) respectively at an initial concentration of 1mg/l.Kinetics and isotherm modeling studies demonstrated that the experimental data best fit apseudo-first order and Langmuir isotherm model, respectively.The maximum adsorptioncapacities were found to be 1.334 mg/g & 1.667 mg/g for As (III), 3.646 mg/g &2.631mg/gfor As (V) with FePDSD and FePASD respectively. In summary, Dalbergia sissoo & Arundodonax sawdusts can be used as an efficient and economical material for the adsorptive removal of As (III) and As (V) from aqueous system.
Studies on the Development of Natural Cation Exchanger for Heavy Metals Removal
(Faculty of Chemistry, 2012) Homagai, Puspa Lal
Two types of novel bioadsorbents such as charred xanthated sugarcane bagasse (CXSB) and charred aminated sugarcane bagasse (CASB)are investigated. This research work elucidates the uptake performance of biosorbent for the sequestration of heavy metal ions such as Cd ,Pb 2+ , Cu 2+ , Ni 2+ and Zn 2+ , respectively. Xanthated and aminated biosorbent prepared from sugarcane bagasse under specific experimental conditions were characterized with FT-IR,TGA/DTA, SEM, Zeta potential and Elemental analysis. Batch adsorption experiments were performed at eight different initial metal ionconcentrations (25, 50,100, 200, 400, 600, 800, 1000 mg/L), at 293 K temperature, while pH of the solutions was varied from 1 to 7. The results indicated that the uptake performance of CXSB and CASB biosorbent significantly changed with pH, concentration of metal ions and temperature. The selectivity order in the removal of heavy metals at pH around 4 follows theorder Pb> Cu > Ni > Cd >Zn for CXSB whereas the order Pb> Cd > Zn > Ni >Cu for CASB. Moreover Irwing-Williams Series support the bindings’mechanism for Cu ,Zn 2+ and Ni 2+ ions ontoboth the modified biopolymers. Adsorption of heavy metal ions onto both CXSB and CASB biosobents followed pseudo-second order kinetics with faster adsorption within 15 minutes to 40 minutes.All the obtaineddatawell followed the Langmuiradsorption isotherm.The positive value of enthalpy change (H) and negative of free energy change (G) shows the adsorption process is endothermic and spontaneous. Moreover, the obtained positive entropy changes (S) shows that an increase in randomness, is associated with the adsorption of metal ions onto the CXSB and CASB biosorbents. As in the case of plastic materials like commercial synthetic cation exchanger, the CXSB and CASB based on sugarcane bagasse developed in our laboratory revealed to be an efficientcation exchanger for removing cadmium, lead, copper, nickel and zinc ions from the aqueoussolution. Keywords:Adsorption, xanthation, amination, heavy metals, sugarcane bassage.
Study of Toxic Chemicals Present in Mosquito Repellants
(Department of Chemistry, 2012) Shrestha, Khem Raj
Household pests such as mosquitoes, houseflies, cockroaches etc are important vectors for communicable diseases like malaria, dengue etc. The mosquito repellants are widely used as the insecticides to control the mosquitoes in households. The active ingredients of the mosquito coil are pyrethroid previously called as pyrethrins. This dissertatione valuated the practice of use of different types of mosquito repellants in the selected population and analyzed the chemical constituents present in mosquito repellants with aneffort to propose a standard protocol. Altogether 120 respondents were selected randomly for the survey. A semi-structured questionnaire was prepared. In the chemical analysis, a total of six solid forms of repellants and three liquid forms of mosquito repellants were included. The solid repellants were extracted by using soxlet extraction and shaking extraction method. For soxlet extraction 95%ethanol was used as solvent where as for shakingextr action method mixture of solution of formic acid and toluene in the ratio of 5:1 was used as solvent. The crude extractsobtained after the extraction was subjected to thin layer chromatography followed by column chromatography with aview to identify the compounds present in them. Gas generated by burning the coil of mosquito repellants was also analyzed. Gaschromatography coupled with mass spectroscopy (GC-MS) was conducted only for the residual solution obtained from smoke after burning the coil. The carbonyl content of the Suryamosquito coil and Octagon Good Knightmosquitocoil samples after burning the respective mosquito coils were analyzed by dinitro-salisylic acid (DNS) method. Among the respondents, 76% respondents were found to use the chemical agent as the mosquito repellants and rest of them usesnet.Among the chemical repellant users, liquid was used by 70%, coil by 22%, mat by 6% and cream by 2% of respondent. In carbonyl compound analysis,Octagon Good KnightandSuryamosquitocoil were found to contain4.44mg/mLand 4.78 mg/mLof carbonyl compoundsrespectively. The GC-MS analysisshows that the residual solution of gas collected after burning the Suryamosquitocoil and Octagon Good Knightmosquitocoil samples were found to containallethrin, palmiticacid, acridine, cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-propenyl)-,2-methyl-4-oxo-3-(2,4-pentadienyl)-2-cyclopenten-1-yl ester, stearic acid, decanoic acid(carpic acid), octadecanoic acid, hexadecanoic acid, n-heptadecanol-1,3-pentanol-2,3-dimethyl, benzyl benzoate, anthraquinone-2-methyl and cholestadiene.
Investigation on the Adsorption Behaviour of lead (Ii) onto Rice Husk Powder
(Department of Chemistry, 2012) Das, Vijay
The application of low-cost adsorbents obtained from agricultural wastes as analternate to the conventional methods of removing heavy metalions from waste water has been investigated. Present study deals with the adsorption of lead (II) from aqueous solution on rice husk and it’s chemically modified form. Rice Husk is a by-product generally obtained from rice mill.The Chemically Modified Rice Husk (CMRH) is obtained by treating raw ricehusk with 4M sulfuric acid. Batch studies were performed at an initial concentration of 25 mg/L to evaluate the influence of various parameters like pH,equilibrium time, amount of adsorbent and concentration of adsorbate. Studies showed that pH of aqueous solution affected lead (II)adsorption as a result the removal efficiency increased with increasing pH of the solution.The maximum efficiency was achieved at pH 5.Kinetics and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-second order and Langmuir isotherm model, respectively. The maximum Langmuiradsorption capacity was found to be 143.25 mg/g &133.81 for CMRH and RRH, respectively. Furthermore, the studies showed CMRH was more favorable than RRH for the adsorption of lead (II)from aqueous solution.In summary, biosorption onto rice husk is a low cost, effective and simple process for treating Pb(II) loaded waste water.

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