(397o) Evaluation of Sugar Beet Processing Lime Cake for the Removal of Synthetic Dyes from Aqueous Solutions

Waste management is one of the most important issues in industries. Their (re)-utilization provide additional revenue that has potential to decrease the process costs. In traditional sugar beet processing, the sugar is extracted from plants and non-sugar components are removed by precipitation. During the process, the impurities are flocculated via sequential addition of limewater (milk of lime and calcium hydroxide suspension) and carbon dioxide. The resultant precipitate contains a significant amount of calcium carbonate and also minerals, nitrogenous- and phosphoric compounds. The content of the sludge slightly varies with the technology and the raw material utilized. In the literature, the waste material has several names such as filter cake, spent lime or sugar beet processing lime waste, etc. Due to its content, the vast amount of sugar beet processing lime waste (SBPLW) is difficult to be disposed and cause severe environmental and ecological problems.

(Efficient management of the waste materials is one of the most important issues in industries. Their (re)-utilization provide additional revenue is also directly decreasing the production costs. In traditional sugar beet processing, the product is extracted from plants and non-sugar components are removed by precipitation. During the process, the impurities are flocculated via sequential addition of limewater (milk of lime and calcium hydroxide suspension) and carbon dioxide. The resultant precipitate contains a significant amount of calcium carbonate and also minerals, nitrogenous- and phosphoric compounds. The content of the sludge slightly varies with the technology and the raw material utilized. In the literature, the waste material has several names such as filter cake, spent lime or sugar beet processing lime waste, etc. Due to its content, the vast amount of sugar beet processing lime waste (SBPLW) is difficult to be disposed and cause severe environmental and ecological problems.)

Previously, several types of applications have been proposed for SBPLW. It was evaluated in desulphurization of fuel gases, animal feed preparations and soil amending. Due to the high amount of calcium carbonate (CC), SBPLW was also used to replace CC to save the natural reserves. It was tested to be used in paper mills and composite preparations. Currently, most of the sugar companies send the waste material to the other industries to be used as a filling material in cement, breeze block and foam concrete productions. However, SBPLW may be used in a relatively more critical objective prior to this low-value handling.

In this study, SBPLW was evaluated to be used in the removal of synthetic dyes from aqueous solutions. Synthetic dyes in aqueous streams are poisonous to human life as well as habitat. Before their discharge, the toxic dyes in aqueous streams and solutions should be removed. Methylene Blue (MB) was chosen as the model synthetic dyestuff in experimental studies. Firstly, the basic characterization of SBPLW was performed and then equilibrium, kinetic and thermodynamic studies were conducted. Experiments were carried out in a broad range of MB concentration. The results were compared with those obtained with commercially available active carbon.

The characterization of SBPLW was carried out by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectrophotometry (EDX). The removal process reached equilibrium within 240 minutes and the kinetic parameters were calculated. The influence of initial pH of aqueous MB solution on adsorption was examined in the pH range of 3–10 and the maximum removal was obtained at pH 4.6 as 76.1% using an MB solution having 200 ppm. Isotherms were applied to the results to figure out which model describes better among the ones tested in this study. Consistent with the literature, adsorption efficiency decreased with the increase in MB concentration and increased with adsorbent dose. Temperature negatively affected the MB adsorption and the thermodynamic parameters were calculated for the adsorption process using SBPLW. According to the values, this adsorption process is a physical process.