Aplicação de sabões de ácidos graxos epoxidados como inibidores de corrosão em oleoduto

Corrosion usually occurs in pipelines, so that it is necessary to develop new surface treatments to control it. Surfactants have played an outstanding role in this field due to its capacity of adsorbing on metal surfaces, resulting in interfaces with structures that protect the metal at low surfactant concentrations. The appearance of new surfactants is a contribution to the area, as they increase the possibility of corrosion control at specific conditions that a particular oil field presents. The aim of this work is to synthesize the surfactants sodium 12 hydroxyocadecenoate (SAR), sodium 9,10-epoxy-12 hydroxyocadecanoate (SEAR), and sodium 9,10:12,13-diepoxy-octadecanoate (SEAL) and apply them as corrosion inhibitors, studying their action in environments with different salinities and at different temperatures. The conditions used in this work were chosen in order to reproduce oil field reality. The study of the micellization of these surfactants in the liquid-gas interface was carried out using surface tensiometry. It was observed that cmc increased as salt concentration was increased, and temperature and pH were decreased, while cmc decreased with the addition of two epoxy groups in the molecule. Using the values of cmc and the Gibbs equation, the values of Gibbs free energy of adsorption, area per adsorbed molecule, and surface excess were calculated. The surface excess increases as salt concentration and temperature decreases, increasing as pH is increased. The area per adsorbed molecule and the free energy of adsorption decrease with salt concentration, temperature, and pH increase. SAXS results showed that the addition of epoxy group in surfactant structure results in a decrease in the repulsion between the micelles, favoring the formation of more oblong micellar structures, ensuring a better efficiency of metal coverage. The increase in salt and surfactant concentrations provides an increase in micellar diameter. It was shown that the increase in temperature does not influence micellar structure, indicating thermal stability that is advantageous for use as corrosion inhibitor. The results of inhibition efficiency for the surfactants SEAR and SEAL were considered the best ones. Above cmc, adsorption occurred by the migration of micelles from the bulk of the solution to the metal surface, while at concentrations below cmc film formation must be due to the adsorption of semi-micellar and monomeric structures, certainly due to the presence of the epoxy group, which allows side interactions of the molecule with the metal surface. The metal resistance to corrosion presented values of 90% of efficiency. The application of Langmuir and Frumkin isotherms showed that the later gives a better description of adsorption because the model takes into account side interactions from the adsorbing molecules. Wettability results showed that micelle formation on the solid surface occurs at concentrations in the magnitude of 10-3 M, which isthe value found in the cmc study. This value also justifies the maximum efficiencies obtained for the measurements of corrosion resistance at this concentration. The values of contact angle as a function of time suggest that adsorption increases with time, due to the formation of micellar structures on metal surface

Serviço Social e terceiro setor: considerações sobre as atuais relações e condições de trabalho para o Assistente Social em Natal

The present study analyses the actual relations and work conditions found in the third sector in Natal city, in the context of productive restoration and increasingly retraction from the State in providing Social Service before the new approach that has been destined to the social issue. The study talks about the work of the social worker when fighting the different expressions the social issue has, such as social service provision as a way of teamwork associated to work relations and conditions, to accessible resources and quality control management. These are elements that affect and interfere in the accomplishment and in the work of the social worker itself. The State s improvement, according to neoliberal-political precepts and increasingly retraction from the public investment in the areas of social concern (health, social welfare, assistance) and in the wage and employment policy, besides expanding the partnership with the public and private areas, in search for social services with quality, it has diversified the structures of the professional work with the growth of the so called third sector institutions. However, the absorption of the social workers by the third sector groups in general, has as major features the impoverishment of work relations, the maintenance of an unequal salary model, pointing out the deadline contracts and/or single tasks that generate work instability. The research debates, with a critical view and full perspective, over the conception of the third sector, interpreted as an action that expresses functions and values, treated as a real phenomenon generated from the restoration of the capital based on neoliberal principles. This study aims for responding what the established work relations are and under what work conditions the social worker has been fitting in the third sector and how such a reality echoes in the current work conditions for a social work in the city of Natal, before this new model of state intervention that transfers part of the social service provision to distinctive divisions of society, among them the so called third sector. The research results have shown that like the other workers the social worker passes through the same crises, dilemmas, advances and challenges that occur in the world of employment and which are expressed in the drop of salary average in the growth of contemporary contracts, unemployment, and in the ever more selective requirements to one be included in the social spaces, where the professional work is done, having as a result a greater impoverishment of work relations and conditions as well as more vulnerability as a salaried occupation

Cultivo de algas marinhas como desenvolvimento de comunidades costeiras

In northeastern Brazil, the extraction of agar has increased considerably in recent decades mainly using macroalgae of the genus Gracilaria. The pressure of the harvest of seaweed of this genus has compromised the sustainability of this natural resource. Given the current framework of decline in production of algae in the state of Rio Grande do Norte, it is necessary the deployment of crops that will assist in the development of coastal areas. This research aimed to develop studies on growth, productivity, efficiency and quality of agar of G. birdiae so as to provide subsidies for crops on commercial scale. The study was carried out in dry and rainy periods using rafts of cultivation. Algal biomass and the physical and chemical parameters of water were measured every fifteen days. In laboratory, the resistance and quality of agar were analyzed. The relative growth rate (TCR) was determined by the formula: RGR = ln (final weight / weight initial). 100 / interval time of sampling. During the study, environmental factors as salinity and temperature remained relatively constant (around 35 PSU and 28°C, respectively). The mean values of biomass ranged around 1952.67 ± 576g in the rainy period and 1925.67 ± 450g in the dry period, and they presented no significant variations. The maximum value of growth (TCR) was recorded in the dry season (7.45%.day-1), with an average over the study of 4.35%.day-1. The yield of agar ranged from 22% to 15%, and its resistance ranged from 850 to 650g. cm². The average obtained for the two periods was approximately 750 g cm². These results demonstrate the great potential of Gracilaria birdiae for mariculture can be used as an sustainable activity for coastal communities