Paper Title
Effect of pH on Chromium (VI) Adsorption from Oak Sawdust as an Alternative for Wastewater Treatment

Abstract
The presence of chromium (VI) in aqueous ecosystems has become a growing problem, affecting the living beings that constitute the ecosystem. According to the World Health Organization (WHO), the maximum limit concentration of chromium in water should be between 0.01-1 ppm;however, concentrationsover 450 ppm has been recorded in effluents. Currently, adsorbents from agro-industrial wastes are being used for the removal of contaminants, due to the proteins, polysaccharides, lipids, and innumerable functional groups that the cellular walls of the biomasses possess, which bind these heavy metals on their surface; for this reason, the use of lignocellulosic materials, such as sawdust from different timber sources is considered to remove heavy metals. Due to its low production cost, abundance of biomasses and ease operation, adsorption using lignocellulosic biomaterials has become a technology of great interest worldwide.The objective of this research was to prepare and characterize a bioadsorbent from oak sawdust for use in the removal of chromium (VI) ions in solution in a batch system. For the study of the effect of pH, the sawdust was characterized by FTIR, pHPZC and Boehm titration; in addition, adsorption essays varying pH from 2 to 7 at an initial concentration of 100ppm using 10 mg of adsorbent were done. Adsorption capacity was found to decrease as pH increases, achieving a 22% reduction from pH 2 to 7; a maximum adsorption capacity of 56.6 mg/g was reached at pH 2. It can be concluded that the efficiency of the adsorption process is highly dependent on the pH of the solution, since the variation of the pH has a significant effect on the existing form of the contaminants (for charged species), the surface chemical properties and the degree of ionization of the adsorbent molecule, determining the affinity of the adsorbate molecules to the adsorbent as a function of the state of both materials. Keywords - Biomass, Lignocellulosic Waste, Sawdust, Hexavalent Chromium.