Biochar as reactive material for heavy metals removal from contaminated water

Several studies have recognized that biochar, obtained from pyrolysis of vegetable waste and by-product from agriculture and forestry, can be considered suitable for its adsorbent characteristics to remove different types of contaminants, both organic and inorganic, from soil and water. In fact, nowadays, due to its distinctive characteristics such as microporosity, high specific surface area, high adsorption capacity and ion exchange capacity, research is focusing on many other possible application of this promising material. A further advantage is the fact that biochar can be considered a sustainable alternative to commercial adsorbents because, being a residual product, its use allows to avoid industrial production as well as to reduce the amount of waste to be disposed. Furthermore, the scientific research, concerning the presence and the removal of pollutants from contaminated water, particularly persistent as heavy metals, is still evolving. In this Ph.D. thesis, biochar will be investigated as a potential adsorbent media for heavy metals removal – in particular arsenic and lead – from contaminated water. Compared to commercial adsorbents biochar represents a new valid alternative from an economic and environmental point of view with good application prospects in many fields. As a consequence, the interest in this material has grown enormously, due to its ability to improve the physical, chemical, biological and mechanical properties of the soil. Biochar in Italy has been mainly used, until now, as a soil amendment in agriculture practices. Its capability in playing an adsorbent role can therefore be particularly interesting, focusing on its ability to remove heavy metals from contaminated water. The research was mainly based on experimental activity, after an accurate bibliographic research and acquisition of the literature data, at a multidisciplinary level, in order to understand the emerging research fields of environmental engineering concerning biochar and its multiple use. The first phase of experimental activity will be focused on the determination of the main physical-chemical characteristics of biochar, also carrying out a comparison with a commercial activated carbon. In the successive phases batch and column tests will be used to investigate the performance of biochar, for arsenic and lead removal from aqueous solutions. As regards the batch tests, the data, relating to experimental activities, will be interpreted through the most used models in the case of heavy metals adsorption from contaminated water, for the determination of kinetics and adsorption isotherms. With regard to the experimentation in the column, breakthrough curves will be identified and the characteristic parameters of the system will be used to validate the obtained data. Therefore, starting from the obtained experimental results, biochar may be considered as a useful alternative as adsorbent media for heavy metals removal from contaminated water. Finally, some experimental hypotheses have been suggested in order to continue the research activity, with the aid of further targeted experimental tests.