摘要：Synthetic coagulants currently used to treat dye wastewater in the water treatment industry has been found to produce large amounts of waste and is bad for the environment. The research then presents two different methods of preparingHibiscus Sabdariffaas a natural coagulant which are direct method and freeze-drying method to possibly replace synthetic coagulant in treating dye wastewater. The two different methods of preparing natural coagulantHibiscus Sabdariffaare compared in terms of protein retention and coagulation performance at removing dye from dye wastewater. This is to determine which method of preparation is better at preparing aHibiscus Sabdariffaas a natural coagulant to be used in the water treatment industry. Three analysis are done to determine the optimum concentration ofHibiscus Sabdariffapowder and freeze-drying duration is based on (i) surface morphology, (ii) water solubility and (iii) water activity. Optimum concentration ofHibiscus Sabdariffapowder is 20wt%and 24-hour freeze-drying duration. Another analysis is done to compare protein retention of each methods of preparation using (iv) Fourier Transform Infrared (FTIR) spectroscopy testing. Protein inHibiscus Sabdariffaprepared using freeze drying is completely retained based on Fourier Transform Infrared spectroscopy results. Supporting data of protein retention properties of freeze drying is proven by water activity inHibiscus Sabdariffapowder is at 0.478 and below the 0.6 threshold value. Water activity of 0.478 means that there is not enough water content inHibiscus Sabdariffapowder for microorganisms to grow and degrade the protein. Optimum coagulant dosage and pH value thatHibiscus Sabdariffaprepared using the two different methods best works in is determined based on two experiments called (v) effects of coagulant dosage on dye removal percentage and (vi) effect of pH value of preparation methods on colour removal percentage. Coagulation performance of both preparation methods are also determined using experiment (v) and (vi).Hibiscus Sabdariffaprepared using freeze drying has better coagulation performance with higher colour removal percentage at lower required coagulant dosage and higher dye removal percentage at varied pH values compared to direct method. As a result, freeze drying is better in terms of coagulation performance compared to direct method at preparing natural coagulantHibiscus Sabdariffa. Coagulation performance of natural and chemical coagulant is compared using (vii) jar test comparison between natural and chemical coagulant on colour removal. This is to determine if coagulation performance of natural coagulant is comparable to chemical coagulant. Coagulation performance of natural coagulant is only slightly lower than synthetic coagulant at colour removal percentage of 91.2% compared to 92.3%. This makes the coagulation performance of natural coagulant comparable to synthetic coagulant allowing it to be an alternative to synthetic coagulant based on coagulation performance. Therefore, Life Cycle Analysis (LCA) will then be conducted to compare the better method of preparation of natural coagulant which is freeze-drying of natural coagulantHibiscus Sabdariffato chemical coagulant alum. Life Cycle Analysis done is to determine, evaluate and compare natural against chemical coagulant based on 3 sustainability aspects economic, environment and social aspects. This is to determine the feasibility of natural coagulantHibiscus Sabdariffain the water treatment industry on whether it is a possible alternative or replacement to the currently used synthetic coagulant alum. Based on Life Cycle Analysis natural coagulant is the better alternative compared to chemical coagulant based on impact towards the environment and health and well-being of society. However, the implementation of natural coagulant in the water treatment industry is still not feasible as production cost of natural coagulant is 126.86 times more expensive compared to chemical coagulant. As a result, currentlyHibiscus Sabdariffaas a natural coagulant is not able to replace synthetic coagulant alum in the water treatment industry.
