Composite porous materials for the removal of organic substances from water

The growing demand for clean water clashes with inadequate water availability. Human activities strongly affect the quality of water bodies, inducing their progressive chemical pollution. The sustainable management of water has become a crucial aspect to ensure both the quantity and the quality of water resources needed to support the demand. The limitations of conventional wastewater treatments in addressing the complete removal of contaminants from the effluents require the implementation of legislative measures to reduce the use of certain substances, together with a technological improvement of the treatment plants in order to protect the quality of water. The improvement of conventional treatments is achieved through the optimization of existing processes or their combination with new advanced treatment technologies. Recently, great efforts have been made towards the development of highly effective, robust and cost-effective composite materials to reduce the entering of aqueous contaminants in water bodies. The progress in nanotechnology offers promising solutions to address the water management challenges, thanks to the use of new advanced engineered nanomaterials in wastewater treatment. This thesis investigates the use of different techniques for the preparation of porous composite materials aimed at the removal of organic substances from water by means of adsorption processes or photocatalytic degradation. The micro- or nanosized active component is incorporated in a polymer-based matrix which ensures the formation of a solid composite that can be easily handled without requiring further expensive and time-consuming processes for its recovering from the treated water. The first proposed composite material is based on the valorization of agricultural waste for the preparation of a highly porous adsorbent through its combination with a biopolymer. Although their abundance and particular chemical composition make them promising low-cost adsorbents, the difficulties caused by their recovery after the water treatment may limit their manageability and applicability. The incorporation of an agro-waste powder in a solid porous system can overcome this limitation, without significantly compromising its adsorption capacity. Furthermore, using agro-waste as a low-cost active filler reduces the costs associated with water treatments and the volume of waste derived from food processing. The following porous composite materials include a photoactive nanomaterial inside the polymer-based matrix, for which the removal of organic compounds occurs by the heterogeneous photocatalytic process. This destructive process is indicated for the abatement of recalcitrant organic pollutants, since it may induce their complete mineralization. The incorporation of the active filler is investigated by using two different approaches, specifically an innovative in-situ fabrication procedure to form the nanomaterials directly inside the polymeric matrix, while for the second approach, the combination of the pre-synthetized nanomaterials to the polymer-based solution to obtain the porous composite. Different strategies to improve the photocatalytic performance of the porous composite materials are presented, studying the effect of the formation of heterostructures between the in-situ grown metal oxide and the noble metals on the photocatalytic degradation of organic contaminants. The proposed in-situ fabrication procedure ensures the formation of a metal oxide-based composite, characterized by a high surface area, flexibility and light weight for heterogeneous photocatalytic applications in water treatment, without the need of post-treatment steps for the removal of the photocatalysts from the treated water which may restrict their wide applicability as well as causing secondary pollution. The preliminary results of the incorporation of pre-formed metal oxide nanomaterials in a porous polymeric matrix are then presented, discussing possible future research.