Contamination of surface waters with heavy metals causes concern due to their toxicity, resistance to degradation and adverse effects on human health and aquatic biota. On the other hand, the search for uses and applications of agroindustrial waste has become a priority in the environmental agenda, due to the large volumes generated. Thus, adsorption is presented as an alternative to using these wastes in the treatment of water contaminated with metal ions. The objective of this work was the study of the use and characterisation of adsorbents of an agroindustrial source (palm bagasse) and by-products of the process of obtaining starch (yam and plantain), for its use in the removal of Cr (VI) and Ni (II) ions in a batch system. The adsorption tests were carried out at an initial concentration of 100 ppm ions at 200 rpm using 1 g of material in 100 mL of solution. The adsorbents were characterised by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, micro-elemental analysis, physicochemical analysis and surface area measurement by Brunauer-Emmett-Teller analysis. From the results, it is established that the palm bagasse has a pore volume twice higher than the other biomaterials. It was determined by the adsorption results, for Cr (VI), were superior in all materials to those obtained for Ni (II). The three agroindustrial residues studied presented high percentages of adsorption efficiency, above 70%, with palm bagasse standing out with an adsorption efficiency of 92%; Therefore, the use of these three biomasses is recommended to treat water contaminated with Cr (VI).

In the present paper, the residues of the plantain starch extraction process are proposed as an adsorbent to remove Cr (VI) in a continuous fixed bed-system, varying the temperature in 33, 40, 55, 70 y 76 °C and bed height in the range of 15.5, 30, 65, 100, 114.5 mm. The adsorbent material was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD). The Cr (VI) solution at 100 ppm had contact with the column by gravity, with a flow rate of 0.75 mL/s at the different working conditions. At the end of the process, the residual concentration of the metal was measured by UV-Vis spectroscopy using the standard method for the determination of Cr (VI) in water ASTM D1687-17. From the results, it was established that the bioadsorbent has the presence of hydroxyl, carboxyl and methyl functional groups and that the adsorption process is controlled by electrostatic interactions; the variables evaluated had a significant influence on the process because applying the RSM methodology it was observed that the optimal operating conditions are 81.49 mm of bed height and temperature of 68 ºC. Based on the behavior of the rupture curve, it was found that the bio-material has the potential to be used as a filler in an adsorption column with the purpose of remove Cr (VI).

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