This work reports the modification of cassava peel using phosphoric acid for the removal of methylene blue from aqueous solutions. A central composite design 32+star was employed using as manipulated variables the temperature of modification (113 ° C to 127 ° C), the biomass- phosphoric acid ratio (1: 0.5 to 1: 1,5) and the initial concentration of dye (100 to 800 mg/L); the response variables of the experiment were the percentage of removal and the adsorption capacity. It was found that for the percentage of removal of dye, the most important variable is the temperature, and that the adsorption capacity is favored at high concentrations of dye. The cassava peel modified at the highest temperature (127 ° C) and biomass:acid mass ratio 1:1 showed higher values for both the removal percentage and the adsorption capacity, which were 99.984% and 79.975 mg/g, respectively. The adsorption kinetics was best adjusted to a pseudo second order kinetic model, which indicates that the process is carried out by chemisorption, also, the process was adjusted to Freundlich isotherms, indicating that the adsorption is carried out in multiple layers. [ABSTRACT FROM AUTHOR]
In this paper was studied the use of low-cost materials obtained from plants remains and modified organic matrices to replace the use of conventional methods for removal of heavy metals. So avoiding subsequent problems such as the generation of chemical sludge, and creates an alternative use for materials considered as waste. It is well known that the presence of some of the active components in these materials allow them to efficiently capture metal ions, however, it was found that other factors like pH of solution and concentration of metals also influence this process. In general, acid treatment and a subsequent transformation of materials to active carbon increases sorption capacity. Also, it is the pseudo second order model and the Langmuir isotherm that are the equations most used to describe kinetics and the adsorption behavior. [ABSTRACT FROM AUTHOR]
