Abstract
Rice husks (RH) are the hard-protective coverings of grains of rice and are removed from rice seeds as a side stream during the milling process. The disposal of RH generates a huge problem for rice industry since RH represents about 23% of initial rice seed weight. The valorization of this side stream could solve the disposal problem and reduce the cost of waste treatment. One possible use of the RH is to burn them as fuel for energy and vapor production. The ash obtained during that process is called rice husk ash (RHA). RHA disposal still generates high disposal costs. Different uses are considered for RHA valorization. Regarding the use of RHA as an adsorbent, previous work efforts are focused on water treatment. This concept has potential benefits on both water treatment and waste management. This work provides an assessment of the adsorption capacity of bio-chars prepared from rice husks. Rice husk char (RH-Char), pre-treated rice husk char (PT-Char) and industrial rice husk char (M-Char) are tested as adsorbents for the removal of methylene blue (MB) and ethinylestradiol (EE2). Results show that RH-Char and PT-Char present zeta-potential values near -52 mV and are rich in amorphous SiO2. M-Char shows a zeta-potential value of -32 mV and has crystalline SiO2. The bio-chars remove MB and EE2 efficiently. The adsorption capacity values for MB (in μmol/g ) are 769.2 (RH-Char), 41.2 (PT-Char), and 31.7 (M-Char). The adsorption capacity values for EE2 (in μmol/g) are: 33.1 (RH-Char), 19.1 (PT-Char), and 16.9 (M-Char). The information gathered in this work evidences the potential of rice husks bio-chars for bio-remediation and may in future contribute to the conversion of this side-stream to value-added materials.
