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Utilização de planejamento fatorial no estudo da remoção eletroquímica de íons Pb(II) de fluentes simulados
(Universidade Federal de São Carlos, 2007-07-27) Almeida, Lucio César de; Bocchi, Nerilso; https://lattes.cnpq.br/5930614700886481; https://lattes.cnpq.br/6233656045399753
In this work, the removal of Pb(II) ions from simulated wastewaters, using a flow-through cell under galvanostatic condition was studied. With help of factorial design and response surface methodology, the variables current, electrolyte flow rate and the specific surface area of the three-dimensional cathode used (stainless-steel wool AISI 304) were simultaneously investigated in order to optimize the electrochemical system. Firstly, the specific surface area of the stainless-steel wool used as three-dimensional cathode was estimated. Then, factorial designs were employed on the study of the removal of Pb(II) ions for different values of cathodic current, electrolyte flow rate and mass of the stainless-steel wool (consequently, distinct specific surface areas). Finally, the response surface methodology for optimization of the removal process and the analysis of variance (ANOVA) for evaluation of the quality of the developed fitting models were employed. Higher values of removal efficiency (RE) were obtained for the highest values of cathodic current; RE values above 90% were obtained after 30 min electrolysis. Higher values of current efficiency (CE) (22%) were obtained for intermediate values of current (~ 0.24 A). For values of current in the range of 0.24 to 0.31 A, the CE values were lower, due to occurrence of simultaneous reactions such as reduction of oxygen, water and nitrate. Low CE values were also obtained for current values in the range of 014 A to 0.24 A as not all surface area of the steel wool was operating under mass transport control. The response surfaces developed for RE and CE values as a function of the current and flow rate revealed that the region close to 0.25 A and 250 L h-1 was the best for the removal of Pb(II) ions. In these conditions, the RE and CE values were 93 % and 22 %, respectively. Although the concentration of Pb(II) decreased from 54 mg L-1 to 0.39 mg L-1 after 90 min electrolysis, almost 99 % of removal of Pb(II) ions was achieved after only 40 min electrolysis. A mass-transfer coefficient (km) of 1.8 x 10-5 m s-1 was obtained for the electrochemical reactor.
Titulações potenciométricas de cátions metálicos tendo como eletrodo indicador o sistema Cu/CuY2-
(Universidade Federal de São Carlos, 2007-07-27) Silva, Paulo Henrique Pereira da; Faria, Ronaldo Censi; https://lattes.cnpq.br/8659496864305621; https://lattes.cnpq.br/9876088563651080
In this work a Cu/CuY2- indicator system was used to carry out potentiometric titrations of Cu2+, Co2+, Cd2+, Zn2+ and Mn2+ ions with EDTA solution. A copper wire with 8.32 cm2 of superficial area was used as an indicator electrode. The CuY2- complex was synthesized by reaction between cupric oxide (CuO) and EDTA standard solution (H2Y2-) at a temperature of 85 oC. The titrations were performed in the presence of small concentration of the CuY2- complex. The Cu2+, Co2+, Cd2+ and Zn2+ ions were titrated in sodium acetate buffer solution (pH 4.80) and Mn2+ in TRIS-HCl buffer solution (pH 8.90). A modification in a conventional method for titration of metallic cations with EDTA solutions was performed to improve the response of the system. The modification includes addition of buffer species to the titrant solution. The buffer specie used to prepare solutions was sodium acetate. The influence of the concentration of CuY2- added in the titration performance was investigated and a relation of nM2+/nCuY2- equal or greater than 5 should be used for a better response. During this work other studies were performed, such as the method to obtain carbonate-free sodium and potassium hydroxides solutions as well as the method for the standardization of EDTA solid reagent, Na2H2Y, to employing as secondary standard in the directly preparation of EDTA solution.
Estudo de painéis de alvenaria estrutural sujeitos a ações perpendiculares ao plano
(Universidade Federal de São Carlos, 2007-07-27) Maluf, Danilo Rodrigues; Parsekian, Guilherme Aris; https://lattes.cnpq.br/7798651726059215; https://lattes.cnpq.br/3770989340770862
There are several cases of out-of-plane loaded masonry such as earth retaining walls, water reservoir, wind loaded panels and other. Thus, there is a lack of Brazilian technical literature in this topic. The aim of this thesis is to fulfill this lack and to be as a reference text to design such structures. The litterature review covers recommendations from several international references. The compiled analysis of those text tries to bring these to the Brazilian materials and technical approach. Several plastic methods to analyze masonry panels are presented and results from using these method to assess the required reinforcement are compared. A comparative analyses taking into account the Limit State and Allowable Stress design methods, considerind requirements from different intenational codes as MSJC 2005, ENV 1996 1 Eurocode 6 - Part 1-1 e 1-2, preliminary review version of NBR 10837/Sep.2005, BS 5628 1/1992; BS 5628 2/1995; BS 5628 5/1992), SAA AS 3700/1998 and CSA S304. 1/1994, are presented. As a closure a complete design example of a masonry panel case, a warehouse panel designed to resist lateral wind forces, is presented.