EXPERIMENTAL PLANNING APPLIED IN THE STUDY OF BIOSSORPTION WITH USED LUBRICATING OILS
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: Used lubricating oil, Experimental Planning, Extraction of heavy metals, Biossorption process
Environmental agencies, society in general and petroleum companies have been increasingly concerned with the handling and destination of automotive oils in view of their growing use and the resulting damages upon disposal. In Brazil, the volume of used oils that must be disposed of in one year is as high as 400.000 m3, provided basically by automotive and industrial lubrication activities. Such residues cotain metals like Fe, Mn, Cu and Zn, generated by engine operation. The environmental impact caused by the increasing generation of residues and the complexity of the new types of industrialized compounds, not always biodegradable, have required the development of novel technologies that reduce or minimize the amount of polutants disposed in the environment. The use of algae to extract heavy metals by biossorption process has proven to be an alternative to enable the treatment of effluents. Sea algae feature the following basic advantages: low cost, high heavy metal sorption capacity and ease of separation between metals and algae, so that the latter may be reused in new estraction cycles and the metals may be effectively extracted. One of the more common problems encountered in experimental procedures refers to the determination of the effect of one or more parameters on a variable of interest. This problem can be minimized by using experimental planning, so as to obtain a model function or a satisfactory aproximation. As a result, the out put responses observed may be produced upon operation of the input variables. The first step of an experimental planning involves the definition of the factors and answers of interest. After their identification, one must establish the objective to be pursued with the experiments in order to allow for the choice of the most appropriate planning. In this work, the influence of some variables on the process of extraction of heavy metals from used lubricating oils has been investigated. Several conditions typical to the biossorption process have been assessed aiming to determine the operation requirements to optimize the metal removal employing sea algae. The answer of interest was the percentage of heavy metal removal. A 24 factor planning with central point has been selected. The following variables have been chosen to compose the procedure: (1) stirring speed; (2) temperature; (3) amount of biomass; (4) concentration of hydrochloric acid during protonation. Analyses involving the statistical importance of input variables and their interactions with the output variables have been made with respect to the evaluation of level curves, “Pareto” diagrams and anove table results, all acquired with the software STATISTICA for windows, version 6.0. Hence, it was possible to generate a model function that translates the level of influence of each variable upon the answers observed.
