Coagulation is a well-known technology applied in water and wastewater treatment. Inorganic salts, such as alum, ferrous sulfate, and polyaluminum chloride, are usually used. It is widely known that utilization of these inorganic coagulants poses several disadvantages, such as high coagulant cost and high sludge volume that increase water treatment expenses. The use of alum also poses health risk to human as it may cause degenerative diseases. In order to minimize these disadvantages, the use of various coagulants from natural resources has been recently proposed. In this research, study was performed on the extraction and use of a potential natural coagulant (Leucaena leucocephala) seed kernel as natural coagulant. Leucaena seed kernel was extracted at various NaCl concentrations (0-5 mol L −1). Extract with highest protein content obtained at NaCl concentration of 3 mol L −1 was further used to treat a synthetic wastewater model substance (Congo red solution) at various pH (2-10) and dosage (2-40 mL L −1). This natural coagulant successfully removed 99.9% of the color at pH 3 and dosage 10 mL L −1 , with only half sludge volume discharged when compared to alum. The result suggests that leucaena is a promising natural coagulant for water and wastewater treatment.
Natural coagulants from plants resources have gained a lot of attention as it is renewable, biodegradable, non-hazardous, lower cost, and less sludge generated compared to chemical coagulants. However there are still some drawbacks, namely long settling time and possible increase of dissolved organic carbon in the treated water. In this paper we tried to address these drawbacks by utilizing citrate modified Fe3O4 to adsorb protein from Leucaena leucocephala as the active coagulating agent. The effect of trisodium citrate concentration and protein adsorption pH to the adsorbed protein was investigated. It was found that the trisodium citrate concentration of 0.5 M and pH 4.0 gave the highest protein adsorption. The obtained magnetic coagulant was furthermore characterized using Scanning Electron Microscopy, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, and Transmission Electron Microscopy to observe the characteristics before and after protein adsorption. Furthermore, the effect of pH (2 to 10) and coagulant dosage (60 to 600 mg L− 1) to the removal of synthetic Congo red wastewater and sludge volume formation was investigated. It was found that pH 3 was the best pH for coagulation due to charge neutralization mechanism of leucaena protein. Furthermore the highest removal was obtained at dosage 420 mg L− 1 with 80% removal. This result was comparable with crude extract of leucaena with half settling time (20 min) and lower increase of permanganate value, indicating lower increase of dissolved organics in the treated water.
Coagulation and flocculation are commonly used in water and wastewater treatment. Inorganic coagulant such as alum (Al2(SO4)3), ferrous sulphate (FeSO4), and polyaluminium chloride (PAC) are commonly used. These coagulants are known for its effectiveness and simple operation procedure. However, there are some drawbacks such as reduction in pH, potential negative health effect when the treated water is consumed, and large sludge volume. To overcome these problems, utilization of natural coagulants has been proposed. Based on its active coagulating agent, natural coagulant could be divided as polyphenolic, polysaccharides, and protein. Protein from beans and seeds is commonly used as the source of active coagulating agent, due to its effectiveness, availability, and relatively simple pretreatment is needed. Usually the protein is extracted by using 0.5-1 M NaCl solution as globulin is the major protein fraction in beans.The extracted protein could act as cationic polymer to neutralize negatively charged colloids through adsorption-charge neutralization mechanism. Extracted protein could work effectively to treat turbid and waste water with lower cost compared to alum. However, most of existing studies are still focused on small – pilot scale utilization thus further explorations are still needed.A B S T R A KKoagulasi dan flokulasi merupakan proses yang umum digunakan dalam pengolahan air dan limbah cair. Pada umumnya digunakan koagulan seperti alum (Al2(SO4)3), ferro sulfat (FeSO4), dan polialuminium klorida (PAC). Selain efektif, koagulasi merupakan proses yang relatif sederhana dan mudah diterapkan. Akan tetapi koagulasi dengan koagulan anorganik memiliki beberapa kekurangan seperti menurunnya pH menjadi asam saat digunakan, potensi gangguan kesehatan jika air hasil pengolahan terkonsumsi, serta volume sludge yang dihasilkan relatif tinggi. Penggunaan koagulan alami menjadi alternatif dalam pengolahan air untuk mengatasi berbagai kekurangan tersebut. Berdasarkan bahan aktif koagulannya, koagulan alami dapat dibagi menjadi polifenol, polisakarida, dan protein. Protein dari kacang-kacangan merupakan salah satu sumber koagulan alami yang umum digunakan, karena selain efektif, kacang-kacangan mudah didapat, serta membutuhkan perlakuan yang relatif sederhana, meliputi pengeringan, pengecilan ukuran, ekstraksi, serta purifikasi. Proses ekstraksi kacang-kacangan pada umumnya menggunakan larutan garam NaCl dengan konsentrasi 0,5-1 M, dikarenakan fraksi protein dominan pada protein kacang-kacangan pada umumnya berupa globulin. Protein yang terekstrak berfungsi sebagai polimer kationik yang cocok digunakan untuk mengolah koloid yang bermuatan negatif melalui mekanisme adsorpsi-netralisasi muatan. Pemanfaatan ekstrak protein dapat bekerja efektif untuk mengolah kekeruhan dan air limbah, dengan biaya yang lebih rendah dibandingkan alum. Akan tetapi pemanfaatannya masih pada skala laboratorium-pilot, sehingga diperlukan pengembangan lebih lanjut untuk isolasi ekstrak serta aplikasinya pada skala industri.
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