Postsynthesis modification of a cellulose acetate ultrafiltration membrane for applications in water and wastewater treatment

A technique for postsynthesis modification of a cellulose acetate ultrafiltration membrane with possible application in water and wastewater treatment is studied. The technique used an oxidizing agent (persulfate) to develop free radicals on the membrane surface, and that was expected to promote grafting of hydrophilic macromolecules (polyethylene glycol). A chain-transfer agent (2-mercaptoethanol) was tested to control the grafting process, avoiding the formation of long chains that usually lead to high permeability losses in other graft techniques. The modifications aimed at the decrease of the fouling susceptibility of the membrane studied. The possibility of an increase in rejection was also investigated. The membrane was characterized before and after modification, by attenuated total reflectance-Fourier transform-infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and in terms of the rejection of neutral reference solutes. The information given by the different techniques of characterization provided strong evidences of the occurrence of modification, although permeation of (real) foulants was the decisive test. To obtain information about the fouling tendency of the nonmodified and modified membranes, two different kinds of foulants were used: a humic acid (usually found in surface waters) and textile auxiliaries (representing one of the most important industries in Portugal). The results showed an increase in the rejections of the humic acid, and significant improvements in the performance of the membrane with respect to fouling tendency in the case of the textile auxiliarie

Managing a non-profit hospitality platform conversion: The case of Couchsurfing.com

Couchsurfing (CS) was founded in 2003 as a non-profit for those interested in creating a common resource for world-wide hospitality exchange and low cost tourism. Built around a non-market communal sharing model, it became a for-profit in August 2011. Applying a discourse relational model approach, this study characterizes how competing discursive articulations over the conversion led to a discursive strategy of moral justification as management sought to retain its non-profit, alternative, democratic imaginary. The study finds that the justifications gained initial appeal, but ultimately lost credibility due to a mismanaged conversion. By articulating the competing discourses through the sacred value protection model (SVPM), this study provides insights into the way in which a management strategy can be interpreted at a micro-analysis level. It recommends that management decisions need to start from the activities of the organizations members, groups and networks so as to account for their emotions, motivations and actions

Transforming product oriented businesses towards service providers: A case study of service design at Siemens Cranes

Although in a service economy a large portion of the gross domestic product is the result of rendered services, some sectors or business clusters are only lately witnessing the emergence of service provisioning in their industries. In the case of Siemens Cranes, which primary focusses on large crane projects and the sale of electrical subsystems, an increase in the need for additional service is currently being witnessed in the container cranes industry. Specifically the end users, in this case the container terminals, are requiring additional service in order to improve their overall efficiency and effectiveness of their core business. Although selling both goods and services can be pursued by a single firm, providing services differs from selling goods. Providing services requires different strategies, processes and methods in order to develop, manage, sell and innovate services. The goal of this thesis is to increase the understanding of redesigning services by researching current business models and the needs of the end users in order to ultimately create a competitive service through the service dominant perspective.Systems Engineering, Policy Analysis and ManagementInformation and Communication TechnologyTechnology, Policy and Managemen

Nanofiltration of nonionic surfactants: effect of the molecular weight cutoff and contact angle on flux behavior

Nonionic surfactants are widely used in industry, and large amounts of wastewater containing nonionic surfactants are produced each year. Nanofiltration (NF) is a possible option to purify these waters, reducing the overall water consumption and enhancing biological purification. However, the flux behavior of NF during purification of wastewaters containing nonionic surfactants is not well understood. NF tests were performed with both synthetic solutions and real wastewaters containing nonionic surfactants from carpet rinsing. When a membrane with a relatively high molecular weight cutoff (MWCO) was chosen, flux decreased to a level lower than that with most ultrafiltration membranes. When a low MWCO was chosen, flux either increased above pure water flux when a relatively hydrophobic membrane was chosen or decreased when a relatively hydrophilic membrane was chosen. NF thus seems feasible to reduce water usage in industrial processes involving nonionic surfactants when a proper membrane is selected. It appeared that flux is controlled by three mechanisms: first, the narrowing of membrane pores through adsorption of monomers when the MWCO is comparable or larger than the monomer size, causing flux decline; second, an improved wettability of the membrane surface through adsorption of monomers on hydrophobic groups, causing flux to increase above pure water flux; third, a decreased wettability through adsorption of monomers on hydrophilic groups, causing flux decline. The nonionic surfactant concentration, MWCO, and membrane's hydrophilicity determine which mechanism is dominant.Geert Cornelis, Katleen Boussu, Bart Van der Bruggen, Ilse Devreese and Carlo Vandecasteel