Production and characterization of ginger (Zingiber officinale Roscoe) as adsorbent of glycerol stream from biodiesel production.

The preparation, characterization and usage of ginger residues as adsorbents of glycerol impurities were evaluated in the present work as an alternative to provide a suitable destination of ginger waste. Many biochars have been used as adsorbents, thus motivating the reuse of different agro-industrial by-products and making the adsorption process suitable for the treatment of industrial waste. Besides, there were no studies using ginger waste as an adsorbent for the purification of glycerol from biodiesel production. The material was characterized in relation to SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy), and BET (Surface Area). After characterization, adsorption was performed initially with the adsorbent after heat treatment. The influence of different variables in adsorption process was evaluated through batch adsorption experiments in which was possible to establish the best experimental conditions. Thus, the contact time varied from 0 to 10 to 30 mg/L and from 0 to 150 s for 60 and 90 mg/L, the temperature ranged from 25 to 45 °C and the initial concentration of glycerol solution ranged from 30 to 90 mg/L while the adsorbent mass was kept at 0.05 g. Another analysis was made to obtain equilibrium data. In this case, the experiments were conducted by the addition of 0.05 g of adsorbent in a 25 mL of glycerin solution at various concentrations, whereas temperature and agitation was constant. A comparative analysis among ginger adsorbents, provided by chemical and thermal treatment, and commercial adsorbents such as clay and activated carbon was also made in order to determine its adsorbent capacity. These experiments were carried out at the best-operating conditions determined previously. The results indicated that the analysis by specific surface area (BET) showed that there was a small variation of the same order of magnitude in the surface area (13.18 m²/g), diameter (125.02 Å), and volume of the pores (0.017 cm³/g), indicating the presence of adsorbate in the adsorbent. The pore diameters of the adsorbents showed mesoporosity. Ginger residues thermally treated showed comparable adsorbent capacity to clay as impurity removal obtained was 75%. These results were better than those obtained with commercial activated carbon after chemical treatment (57%). The kinetic modeling demonstrated a better adjustment of pseudo-first-order, pseudo-second-order, and Elovich models to experimental data, suggesting the controlling steps of adsorption impurities is governed by a simultaneous physisorption-chemisorption mechanism. Thus, the material proved to be a promising alternative adsorbent in the removal of glycerol impurities. [ABSTRACT FROM AUTHOR]