“Development and characterization of innovative adsorbent materials for the remediation of contaminated water”

The present thesis deeply investigated the use of a commercial innovative material, the thermoplasma-expanded graphite (TPEG), as adsorbent material for water remediation. This innovative material has never been used for this kind of applications and this thesis would demonstrate its effective use for water and groudwater remediation. TPEG is a promising material for that purpose due to its characteristics, evidenced by the producer, such as: high surface area and very significative expansion of interlayer distance of the plan of graphite. The commercial form of the TPEG is a very light powder that floats on the water, therefore, it was used in its natural form in batch tests. Adsorption of different pollutants, such as methylene blue, thricloethylene and diclofenac, was deeply investigated by evaluating the kinetics and isothermal aspect of the adsorption. Furthermore, other parameters that can affect the adsorption, such as pH, initial concentration of pollutants, ionic strength or presence of interference, were investigated. The possibility of regenerating and reusing the TPEG as adsorbent was also evaluated. Modification of the morphology of TPEG was conducted in order to use it as adsorbent material for different setup of process, like fixed-bed column. To this aim, the commercial form was transformed into a granular form of thermo-plasma expanded graphite (GTPEG), by entrapping TPEG into calcium alginate, by using a process that was developed and optimized during tihis thesis work. The GTPEG was then used to treat water by adsorption on fixed bed column. The process was deeply investigated and several pollutants were tested as target compounds, such as short chain phthalates (plasticizers), carbamazepine, bisphenol, 1,7-α ethynilestradiol and atrazine. The effect of adsorbent dosage, flow rate, initial concentration of pollutants, time contact and composition of GTPEG was evaluated. Other tests were conducted to verify the leaching of GTPEG. Adams-Bohart and Thomas models can effective applied to modelize the process and to evaluate its scale up. A sonication process was optimised to transform the not soluble TPEG into a hydrosoluble form, useful to treat groundwater by injecting the adsorbent material to obtain a hydraulic barrier able to contain and remove the pollution. By using this hydrosoluble form, TPEG can be used as material for the installation of injectable permeable reactive barrier. The capacity of the hydrosoluble TPEG to adsorb BTEX was firstly tested and characterized by using the batch setup to have all the information on the adsorption process. After the deeply characterization of the adsorption process, the use as injectable permeable reactive barrier to remove BTEX from groundwater was investigated. Innovative commercial materials can be used as adsorbent, but waste materials also represent a source of adsorbent materials. For this reason, a little part of the thesis was reserved to this kind of work. The last chapter reports a study conducted on the reuse of agricultural-food waste as adsorbent material: the spent ground coffee. The ability of spent ground coffee as adsorbent material was demonstrated by deeply investigating its capability to remove methylene blue.