Master of Science By research

Permanent URI for this collectionhttp://192.248.9.226/handle/123/15928

Browse

Browsing Master of Science By research by Author "Adikari, SU"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    item: Thesis-Abstract
    Investigation on sintering behaviour of waste alumina roller material in presence of MgO and ZrO2
    (2014-08-07) Rajasingham, S; Jayaratna, M; Adikari, SU
    In the present study the feasibility of utilization of high alumina roller waste from fast firing kiln was studied. These roller wastes, which contain important quantities of S i 0 2 and Al203, can be used as cheaply available raw material in ceramic product. The sinterability of alumina waste powder at 1400°C, 1500°C 1600°C and 1700°C was studied by density measurement, XRD analysis, microstructural analysis and determination of mechanical properties of those sintered samples. The study was further done by adding Z r 0 2 to the waste in different wt% (2-8wt %) and modified with 10wt% alumina powder. Temperature required for the sintering waste powder to get theoretical density above 95% decreased with the addition of MgO as sintering aid. It showed the addition of MgO in amount above 0.5% promoted densification at 1500°C. At 1600°C, the higher density (-95%) was achieved with addition of MgO in between 0.5% - 1.5%. At higher temperature at 1700°C densification can be achieved with the MgO addition <0.5%. Densification of modified waste with 10% AI2O3 was increased with addition of MgO at 1500°C. The maximum density with (99.9%) was obtained at 0.5% MgO. The XR.D patterns of the MgO added waste powder compacts sintered at temperatures up to 1700°C for 3h showed the presence of mullite and corundum as the major phases in all samples. But Mg-Al Spinel was formed when the samples sintered at 1400°C for 3h. Optical microstructure was porous for samples with excess MgO (>1%) sintered above 1600°C for 3h. The SEM observation of the microstructure showed the grain morphology as spherical at I500°C for 3h, but with increase in sintering temperature to 1600°C for 3h it was observed as elongated rod like grains. Addition of Z r 0 2 acted as sintering aid and above 97% obtained in the sintering temperature range between 1500°C -1600°C. Z r 0 2 addition significantly improved the fracture toughness of the waste powder compacts also. Better mechanical properties such as hardness and strength were obtained for the densified compacts (above 95%). The maximum hardness was given as 5.35GPaq and 6.13GPa for the compositions 100% waste with lwt% MgO (96.3%) and modified with 10% A1203 with 0.5% MgO (99.9%) respectively which were sintered atl500°C for 3h. Maximum MOR values for the above composition were 169.3MPa and 213.25MPa respectively.
  • Thumbnail Image
    item: Thesis-Full-text
    Study on heavy metal adsorption by chitosan biopolymer
    Unagolla, JM; Adikari, SU
    Heavy metal pollution is a serious problem to aquatic ecosystems because some of these metals are potentially toxic even at very low concentrations. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The purpose of this research work was to study the adsorption of cadmium and lead ions into chitosan, produced from shrimp shells at the laboratory level. Shrimp type “penaeus monodon” (giant tiger prawn) was used to synthesis the chitosan. The main characteristic properties such as degree of deacetylation (DD); the amount of amine groups in chitosan, viscosity, crystallinity and thermal analysis were done by using Fourier transform infrared spectroscopy, Brookfield viscometer, X-ray spectroscopy, thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). Chitosan, with a degree of deacetylation between 80%- 95% was used in the experimental part and the flake sizes were smaller than 0.25mm. Experimental work involved the determination of the adsorption isotherms and kinetic studies for each metallic ion in a batch system. Effect of Degree of deacetylation (DD) of the chitosan, effect of initial pH of the metal ion solution, effect of particle size, effect of initial heavy metal concentration, and effect of chitosan dosage were studied. The results showed that the adsorption capacity depends strongly on pH of the solution, DD of chitosan and slightly depends on the particle size. According to the results, pH values at 6.5 for cadmium and pH values at 4.5 for lead show higher adsorption capacity. High DD chitosan showed higher adsorption capacity mainly due to the higher number of active amino groups in high DD sample. Simplified kinetic models such as pseudo-first-order, pseudo-second-order, Elovich model and intra-particle diffusion model were used to determine the rate limiting step. Both linear and non-linear According to the kinetic models pseudo second order model best described the adsorption process. Both linear and non-linear models and Elovich model best described the adsorption process. Multilinearity in the intraparticle diffusion model suggested that the adsorption of heavy metal consists of two major steps, due to the different pore sizes of chitosan. Equilibrium experimental data were analyzed by using two different isotherm models namely, Langmuir and Freundlich. According to the results, adsorption process of cadmium and lead heavy metals is heterogeneous and multilayer adsorption as it best fit with the Freundlich isotherm model. According to the thermodynamic experiments, adsorption process is favorable and physical adsorption was predominant in the adsorption process. Desorption of the heavy metals was possible by using different regeneration solutions.