Synthesis of highly-efficient functionalized biochars from fruit industry waste biomass for the removal of chromium and lead

Plums and apricots are among the most popular fruits in Serbia and kernels of these are generally disposed of as waste. In common with other organic waste products there is potential to utilise these kernels in wastewater treatment. A new generation of highly-efficient biochars were therefore developed for low-cost wastewater treatment. The aim of this work was to prepare functionalized biochars from different fruit industry waste biomass and to evaluate their ability to for lead and chromium adsorption. Fruit kernel based biochars were synthesized by pyrolysis and functionalized with sulphuric acid. The biochars were characterized using: proximate-ultimate analysis, the Brunauer, Emmett and Teller technique, surface functional group analysis with Fourier-transform infrared spectroscopy, pHpzc and scanning electron microscopy with energy dispersive X-ray spectroscopy. Heavy metal adsorption by biochars was studied using different process parameters was shown to occur through different adsorption mechanisms. Three kinetic and two isotherm models were applied to the experimental data. Sulphur-containing functional groups on the biochar surface played an important role in binding. The high adsorption efficiency is attributed to surface complexation of biochar functional groups with heavy metal ions. Based on these results, biochars could be used as a highly efficient adsorbent for removal of heavy metals from aqueous solutions.