Characterisation of Melastoma Malabathricum leaves and cellulose for removal of Methylene Blue in simulated wastewater

Abstract

Colors are an important class of pollutants, and disposal of colors in precious water resources should be prohibited. The regular commercial adsorbent is expensive, so it leads to researches on alternative low-cost adsorbents (LCAs) for such application. In this study, the usage of Melastoma Malabathricum cellulose as an adsorbent is discussed. The aim of the this work is to extract cellulose from Melastoma Malabathricum (senduduk) leaves by alkali and bleaching treatment, characterising and, testing for colour removal of synthetical Methylene Blue colored wastewater. The characterisation techniques are initiated with chemical composition analysis before and after Melastoma Malabathricum cellulose extraction, results in percentage of cellulose increased to 90 % compared to raw leaves. The morphology of raw leaves and isolated cellulose are analysed by scanning electron microscopy (SEM) analysis. A structural analysis was carried out by Fourier transform infrared (FTIR) spectroscopy analysis and thermal stability was investigated by Thermogravimetric (TGA) analysis. The results indicated that the hemicelluloses and lignin were removed extensively from extracted cellulose. The thermal stability, purity and crystallinity of the cellulose were improved at various purification stages when compared to raw material. The adsorption method occupies a prominent place in color removal as it is effective and economical to application level. Thus, this technique is used to investigate the suitable condition for extracted cellulose of melastoma malabathricum by three parameters which are adsorbent dosage (g), initial color concentration (mg/L), and pH of Methylene blue colored wastewater used. Sample A is leaves (cellulose) which were soaked for 3 days/nights while Sample B is leaves (cellulose) soaked for 6 days/nights. By analyzing all the parameters, the color removal indicators prove senduduk cellulose B is the outstanding adsorbent to remove methylene blue efficiently compared to raw leaves and cellulose of sample A and B. The optimum pH for methylene removal by senduduk cellulose B is pH 7. About 69.63 mg/g adsorption capacity is achieved at optimum initial methylene blue concentration 20 mg/L, senduduk cellulose B dosage 0.10 g and pH 7. For percentage COD removal, 91 % reported at an optimum initial methylene blue concentration of 20 mg/L, senduduk cellulose B of dosage 0.10 g and pH 7. Therefore, soaked leaves for 6 days before chemical treatment and cellulose extraction results in better performance as adsorbent to remove color.