| dc.description.abstract | Microalgae are photosynthetic microorganisms, which have both harmful and
useful aspects. In the presence of nutrients in the water bodies, harmful algal
blooms can rapidly develop, affecting the water quality. Therefore, in this study, a
cationic lignin polymer as a flocculant was synthesized to harvest harmful
microalgae from their water medium, for productive applications. Even though
many organic, inorganic, and biopolymers have previously been used as flocculants,
cationic lignin polymers have never been used to harvest microalgae. Extracting
from coconut husks, or recycling the waste generated in pulp industries are some
common ways that lignin can be obtained. Since lignin is abundant in nature and
low in cost, it can be considered an economical raw material. The flocculant was
synthesized by first increasing the active sites of lignin polymer via a phenol pretreatment.
Then secondary amine groups were introduced to the phenolated lignin
polymer via a Mannich reaction and converted into quaternary amine groups. The
formation of the flocculant was confirmed using FTIR analysis. Flocculant was then
used in jar test experiments to find out optimum conditions required for maximum
flocculation efficiency of algae, using water samples collected from Beira Lake, Sri
Lanka. A series of six concentrations (0 mg/L, 5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L,
25 mg/L) of the flocculant at three different pH values (pH 7, pH 8 and pH 9) were
tested to obtain the optimum condition. At pH 8 a maximum flocculation efficiency
of 84% was obtained using 20 mg/L of the flocculant. These preliminary results
suggest that the cationic lignin polymer developed in the current study could be
used as an efficient flocculant for harvesting algae from water samples. | en_US |
