REMOVAL OF COPPER FROM AQUEOUS SOLUTIONS USING BIOCHARS PRODUCED THROUGH PYROLYSIS

摘要

In this study, the biochars of three agricultural by-products (rice husks, olive pomace andorange waste) and compost are evaluated regarding their capability in Cu(ll) adsorptionfrom aqueous solutions.For each material, two kinds of biochars were produced, through pyrolysis at two different temperatures, 300°C and 600°C, respectively. The pyrolysis process was carried out under oxygen-limited conditions in a muffle furnace, where porcelain crucibles containing the materials were placed and kept for six hours.For the evaluation of the adsorption capability of the biochars and the raw materials,batch experiments were performed to investigate the influence of adsorbent dose, pH,contact time and initial Cu(ll) concentration. These experiments were carried out usingplastic flasks with a ratio of solid:liquid of 1:40 (g/mL). The resulting data were used tostudy the adsorption kinetics and adsorption equilibrium.The obtained results showed relatively high Cu(ll) adsorption efficiency onto all tested materials. It was observed that the adsorption process was highly dependent on the experimental conditions. It resulted that the optimum Cu(ll) adsorption conditions determined from this evaluation were: adsorbent dose 5-12.5 g/L, pH 5 - 6 and contact time 2 -4 h. The adsorption kinetics was properly fitted by the pseudo-second order model, for all tested materials. Regarding the adsorption equilibrium, the adsorption systems for five materials were best described by the linear isotherm, while the rest were best described by the Freundlich isotherm.Furthermore, it was also noticed that pyrolyzing the four studied materials at bothtemperatures, 300°C and 600°C respectively, led to a decrease in their adsorptioncapacity, in comparison with the raw materials. This is probably due to the destruction ofsome part of the active sites on the materials surface. However, the adsorption resultsobtained by the 300°C Pyrolysis biochars were higher and more sufficient compared tothe adsorption ability shown by the 600°C Pyrolysis biochars. This could be attributed tothe higher temperature of this process, which consequently caused the destruction ofmore active sites, compared to the 300°C Pyrolysis process.