Extraction Of Cellulose From Agricultural Waste For Water Purification

Abstract

The escalating demand for clean water and rising water shortages due to population growth, improper use, and expanding urbanisation have become a global issue. In most parts of the world freshwater contains of contaminants such as heavy metal ions that are detrimental to human health. Water treatment has thus become important for the removal of any contaminants in water to render it safe for consumption. Continuous membrane and/or filter processes have been shown to be effective in water treatment. In this study, agricultural residue in the form of cellulose based maize stalks was used to extract cellulose which is a renewable and environmentally friendly adsorbent material that contains nano- and micro cellulose membranes. The membranes were prepared from cellulose nanofibers and CNT in the absence and presence of sodium lauryl sulfate (SLS) via vacuum filtration process. To Improve the stability and absorption of contaminants, carbon nanotubes were added into the cellulose membranes. Furthermore, to enhance the dispersion of SWCNTs into the cellulose membranes, SLS was used, and the resultant composite was “termed” the modified composites. The membranes were analysed by means of SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), UV-vis spectroscopy (UV), and thermogravimetric analysis (TGA). The ratios of the investigated cellulose membranes were categorized as follows: cellulose: non-SLS SWCNT 1:0.3, 1:0.5 and 1:1, as well as: cellulose: CNT: SLS 1:0.3:1, 1:0.5:1 and 1:1:1. SEM and TEM images showed that the presence of sodium lauryl sulfate (SLS) resulted in a better dispersion of the carbon nanotubes within the cellulose matrix with few agglomerates of carbon nanotubes being visible. According to the XRD, the incorporation of carbon nanotubes in the form of single-walled carbon nanotubes (SWCNT) and their modification in the form of SLS seemed to cause little or no change in the peak positions. However, the addition of SWCNTs decreased the crystallinity index of the cellulose i.e. 71.5% to 67.1% for cellulose: CNT 1:0.3. The presence of SLS in the composites was demonstrated by symmetric stretching 2843 cm-1 and asymmetric stretching 2910 cm-1 as became evident using FTIR. Generally, as much as the SLS modified system for cellulose (CNT 1:0.3 composites) showed high removal efficiency, the presence of the SLS-based system seemed to hinder the formation of porous structure in the cellulose membrane and, as a result, reduced the adsorption of the dye. The removal efficiency showed that bromophenol blue dye (46.9%) was most adsorbed by cellulose when compared with dylon dye (2.6%). All investigated samples were found to be resistant to calcium carbonate (CaCO 3), sodium hydroxide (NaOH), and nitric acid (HNO3).