Browsing by Subject "Heavy metals"
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Item Adsorption of Cd (II) From Aqueous Solution by Activated Charcoal Derived from Lapsi Seeds(Department of Chemistry, 2009) Lamsal, NirmaThe 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.Item Functionalization of Biopolymers for the Treatment of Heavy Metals from Aqueous Medium(Department of Chemistry, 2014) Kour (Karki), JagjitThe industrial discharge of heavy metals into waters' course is one of the major pollution problems affecting water quality and human health. Therefore, they must be removed prior to their discharge into waste streams. For this novel cause several types of treatment methods are in use. Among them use of biowaste is emerging as the best method. Therefore different types of agricultural by-products have been explored for their efficiency in removing heavy metal ions from aqueous solution. In this regard a biomass of Desmostachya bipinnata (DB) was investigated as the potential bio-adsorbent for the removal of Cd(II), Pb(II), Cu(II) and Zn(II) from wastewater. DB is a sacrificial herb in the south Asian region particular to Hindu religion with medicinal value. It is found to be very effective in the phyto-accumulation of heavy metals from soil as well as from polluted water. This is the first adsorption studies ever performed with DB as the novel bio-sorbent in the removal of heavy metal ions. Nitrogen functional groups were grafted onto the polymeric backbone of DB with hydrazine monohydrate, dimethylamine and ethylenediamine respectively, for the better adsorption. The characterization of biopolymer was done using SEM, DRFTIR, elemental analysis, zeta potential, XRD and TG/DTA. The characterization results of biopolymer revealed to indicate proper functionalization with nitrogen groups. The effect of pH, initial concentration and contact time of the metal solution were monitored by batch method. The maximum adsorption capacities determined for Cd(II), Pb(II) Cu(II) and Zn(II) were 76.8 mg/g, 130.4 mg/g, 72.1 mg/g and 58.16 mg/g, respectively, at their optimum pH. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models. Langmuir isotherm model fitted well and the rate of adsorption followed the pseudo second order kinetic. The experiments on regeneration and reuse of biopolymers were conducted with batch method. The results indicated that more than 90% of heavy vii metals were regenerated and the biopolymers were used for six successive cycles with 90% efficiency. Thus, the adsorbents derived from DB can be used as an effective, efficient, low cost and environment friendly material for the removal of Cd(II), Pb(II), Cu(II) and Zn(II) from the aqueous medium. Keywords: Desmostachya bipinnata, Biosorption, Heavy metals, Batch experiment, Pseudo- second order kinetic model, Functionalization, Low cost, Pollution, Biosorbent.Item Studies on the Potential Application of Bio-Waste for Heavy Metals Removal from Aqueous Solution(Department of Chemistry, 2014-10) Shrestha Raghubanshi, BindraAn efficient and effective biosorbents were investigated by using waste tealeaves. It was prepared by amination with three different aminating reagents to introduce amino groups onto the surface of biosorbent. The biosorbent was animated by using ethylenediamine, dimethylamine and hydrazine monohydrate. They are called CATL-1, CATL-2 and CATL-3, respectively. The prepared biosorbents were characterized with elemental analysis, analysis of cellulose, hemicelluloses and lignin, SEM images, FTIR spectra, XRD analysis, TG/DTA analysis and zeta potential analysis. These aminated biosorbents were used for sequestration of heavy metals like lead, copper, cadmium and zinc. Their metal uptake performance were also elucidated by using batch experiments. The adsorption capacities of biosorbents were studied as the function of solution pH, initial concentration of metal ions and contact time of adsorption. The effect of pH on adsorption were studied by varying the solution pH from 1-7. The results indicated that the uptake performance of biosorbents significantly change with pH of solution and optimum pH for adsorption was also determined. The initial concentration of metal ions varying from 25-800 mg/L were used to calculate the optimum loading capacity of biosorbents. The optimum time for adsorption were determined by contacting the adsorbent with metal solution at different interval of time. The experimental data were found to be well fitted with langmuir isotherm model. From the isotherm plots the maximum adsorption capacities for lead was found to be highest for all of the three adsorbents while the values were lowest for zinc. Among the three biosorbents, CATL-3 is found to be having highest adsorption capacity for all metal ions used in this study. In CATL-3, the maximum adsorption capacity for Pb (II), Cu (II), Cd (II) and Zn (II) are found to be 120.8, 90.4,114.3 and 79.76 mg/g, respectively. The optimum contact time for metal ions are found to be between 120 - 150 min for all the biosorbents. The kinetic data were well fitted with pseudo - second order model. Hence the biosorbents prepared from waste tealeaves can be potentially applied for treatment of waste water contaminated with toxic heavy metals.