COD and colour removal from molasses spent wash using activated carbon produced from bagasse fly ash of Matahara sugar factory, Oromiya region, Ethiopia

Abstract

The aim of this study was to investigate the removal of chemical oxygen demand (COD) and colour from a melanoidin solution using activated carbon produced from bagasse fly ash (BFA). Melanoidins are heterogeneous polymers and major contributors to the dark brown colour of molasses spent wash, which is an extensive cause of environment pollution. The surface area of the BFA was determined as 160.9 ± 2.8m²/g with 90% of particle less than 156.8 µm in size. Characterization of the BFA by Fourier transform infrared spectroscopy (FTIR) showed the presence of hydroxyl and carbonyl functional groups, whereas X-ray diffraction analysis indicated its amorphous nature. Moreover, scanning electron microscopy analysis showed a heterogeneous and irregular shape of pores. Among the adsorption isotherm models analysed, the Freundlich model fitted best to the experimental data, indicating a maximum adsorptive capacity of 124.80 mg/g. The removal of COD and colour from a melanoidin solution with this activated carbon was carried out using an experimental design taking 4 factors into account. These were adsorbent dose, contact time, pH and initial COD concentration, with removal of COD and colour as response variables. COD reduction was influenced by initial COD concentration whereas colour removal was dominated by contact time, which was in line with the findings of principal component analysis . The maximum COD removal recorded was 61.6% at the optimum condition of adsorbent dose of 4 g in 100 mL, contact time of 4 h, pH 8 and initial COD concentration 6 000 mg/L, whereas the decolourization of melanoidin solution was 64% at adsorbent dose of 4 g, contact time 4 h, pH 3 and initial COD concentration 6 000 mg/L. Hence, activated BFA is a promising option for simultaneous removal of COD and colour from molasses spent wash under the stated conditions.

Fluoride removal from aqueous solution onto activated carbon of Catha edulis through the adsorption treatment technology

“…where the MC% is moisture content in percent, VC% is volatile content in percent, Ash% is the ash content in percentage (Nure et al 2017) Determination of pH A 1.0 g of CAC was added to 100 mL of distilled water in a beaker of 500 mL volume in order to determine the pH value of CAC adsorbent. Then, the beaker was covered with a watch glass and boiled on the hot plate for 5 min and set aside for a few minutes to settle the bulk of CAC particles.…”

“…The flasks were agitated at 120 rpm using magnetic stirrers on an orbital shaker for specified contact times labeled. Then, the solution was left to settle for 2 min and the finer particles were removed using Whitman filter paper 42 (Hegazy et al 2014;Nure et al 2017). The filtrate sample was used for the analysis of fluoride removal.…”

“…In comparison with other aforementioned treatment techniques, adsorption of fluoride removal from drinking water is the most appropriate and widely used treatment technique. Flexibility, simplicity of design, relative ease of operation, cost-effectiveness, environmental considerations and production of high water quality are the major advantages of the adsorption treatment technology (Lavecchia et al 2012;Nure et al 2017). However, commercially developed activated carbon is a universal adsorbent and very expensive which makes adsorption unsuitable for developing countries.…”

“…Additionally, the experimental study was designed to use full factorial approach with a 3 3 , which were the three levels of the three independent variables, namely: pH (2, 7 and 9), contact time (60, 90 and 120 min) and adsorbent doses (0.5 g, 1.0 g and 1.5 g in 100 mL). There are many advantages of such factorial experimental designs, some of which require low cost, minimum numbers of experiments, reduced treatment time and the possibility to investigate the main and interaction effects separately (Nure et al 2017).…”

Sugarcane biorefineries wastewater: bioremediation technologies for environmental sustainability

“…Generally, this color-bearing distillery wastewater is a challenge to treat. Among the color causing pigments, melanoidins (C 17 -18 H 26 -27 O 10 N) are the major cause for the dark brown color of the spent wash which is formed under non-enzymatic (Maillard) reaction between sugar and amino compounds at high temperature [26,27]. Melanoidin is described by its unique nature such as the recalcitrant, antioxidant, acidic, nitrogen containing dark brown polymeric compound [28].…”