Development and application of eco-adsorbents in the minimization of residues from winery industry

Resumo

The present Thesis aims at offering a suitable alternative to the current disposal of residues in viticulture and winery industries by giving waste a second life, contributing to the minimization of residues generation, the sustainable development of economy and society and seeking the zero-waste production. The research is focussed on the recovery of grape marc and vineyard pruning waste, both residues from the wine-making sector, to develop eco-adsorbents that could be applied in wastewater treatment; specifically, in vinasses treatment, a residual effluent from wineries. Grape marc is spontaneously biodegraded and entrapped in calcium alginate beads in order to formulate a suitable biocomposite to treat wastewaters. The morphological characteristics of this biopolymer are studied by means of diverse microscope techniques, and a high efficiency as bioadsorbent for micronutrients and coloured compounds removal is observed. Aside with this, the adsorption process is studied at different stages. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms are used to describe equilibrium, whereas the kinetic behaviour is analysed by pseudo-1st, pseudo-2nd, Chien-Clayton and intraparticle diffusion kinetic models, finding that the adsorption process follows Freundlich isotherm, pseudo-second kinetic model and that the adsorption process is physically controlled and partially controlled by intraparticle diffusion. Additionally, a larger comparison is established with biopolymers formulated with other lignocellulosic residues, which are barley husk, peanut shell and sawdust. A biocomposite based on humus is also included in the study for comparative purposes. Apart from their pigments removal capacity, a kinetic analysis is performed as well, observing that their behaviour is similar to that shown by the grape marc-based biocomposite; the adsorption process follows a pseudo-second order kinetic model and the process is partially controlled by intraparticle diffusion. As for the vineyard pruning waste, a natural lipopeptide biosurfactant is included in the formulation of the biocomposite in order to develop a new bioadsorbent. The morphological and adsorptive properties of the new biocomposite are enhanced respect to the regular vineyard pruning waste biocomposite, achieving better results for coloured compounds and for sulphates removal. Moreover, the modified biocomposite shows a rounder and rougher surface, and a better-emulsified internal structure. After studying the kinetic parameters of both modified and non-modified biopolymers, it can be observed that the adsorption process follows a pseudo-second order kinetic model and that the adsorption is first controlled by liquid film diffusion and then by intraparticle diffusion. Finally, a study of the environmental impact associated to the production of these new bioadsorbents compared to the current technologies already available for the production of adsorbents is performed applying the Life Cycle Assessment methodology. Additionally, both lab and larger scales are included in the analysis. The results showed that there is a noticeable difference between these two scales. Whereas electricity is responsible for most of the environmental burden at lab scale, chemicals appear as the most contributing group at a larger scale. This outcome proves that results obtained at lab scale cannot be directly transposed to a larger scale. Moreover, barley husk and grape marc biocomposites were found to be the less environmentally harmful processes.