Biodegradable polymeric flocculants based on cassava starch grafted with polydiallyldimethylammonium chloride
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Date
2016-01-01
Authors
Mohd Amin Ahmad Razali
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Abstract
This research work was conducted to explore the preparation and optimization of grafting process, flocculation behaviour and flocs aggregation characteristic of cassava starch grafted with polydiallyldimethylammonium chloride (polyDADMAC). The optimization process was achieved by using response surface methodology (RSM) comprising three-levels and four-variables central composite design. The optimum condition derived were 1.96 (mole ratio of DADMAC to starch), 40°C (reaction temperature), 0.09 mol/L (initiator concentration) and 4.99 hour (reaction time). The actual experimental yield was 21.98% at optimum conditions, which was close to the maximum predicted value of 22.80%. Subsequently, the biodegradability of grafted samples was investigated by using soil burial method. It was found that higher grafting percentage shows higher weight loss compared to other grafted sample and native starch. The biodegradability was confirmed by analysis their functional groups, molecular weight and morphology of the samples. The effectiveness flocculation of grafted samples was investigated in kaolin suspension. The effectives were based on turbidity and total suspended solid (TSS) removal. It was shown that mechanism for grafted samples are charge neutralization and bridging which occurred concurrently. It was also found that removal was improved with increasing of grafting percentage. The flocculation behaviour was further studied in details by observing the aggregation, breakage and regrowth of flocs using photometric dispersion analyser (PDA). The flocs growth increase with increasing of grafting percentage because of the improvement of interaction between grafted flocculants and suspended. It was reveal the increased of the shear and time will reduce the strength and recovery factor of flocs.