Due to the increase in contamination of aquatic niches by different heavy metals, different technologies have been studied to eliminate these pollutants from contaminated aquatic sources. So the objective of this work was to determine the removal of cobalt (II) in aqueous solution by the biomass of the aquatic lily or water hyacinth (Eichhornia crassipes) which, is one of the main weeds present in fresh water, due to its rapid reproduction, growth, and high competitiveness, by the colorimetric method of the methyl isobutyl ketone. The removal was evaluated at different pHs (4.0–8.0) for 28 h. The effect of temperature in the range from 20 °C to 50 °C and the removal at different initial concentrations of cobalt (II) of 100 to 500 mg/L was also studied. The highest bioadsorption (100 mg/L) was at 28 h, at pH 5.0 and 28 °C, with a removal capacity of 73.1%, which is like some reports in the literature. Regarding the temperature, the highest removal was at 50 °C, at 28 h, with a removal of 89%. At the metal and biomass concentrations analyzed, its removal was 82% with 400–500 mg/L, and 100% with 5 g of natural biomass at 20 h. In addition, this completely removes the metal in situ (100 mg/L in contaminated water, at 7 days of incubation, with 10 g of natural biomass in 100 mL). So, the natural biomass can be used to remove it from industrial wastewater, even if in vivo, only eliminate 17.3% in 4 weeks.

It was studied the removal capacity of Chromium (VI) in an aqueous solution by the modified biomass of rice grain, using the diphenylcarbazide colorimetric method, to evaluate the metal concentration. The biosorption at different pHs (1, 2, 3, and 4) was evaluated at different times. Too, the effect of temperature in the range of 28 to 60 °C and removal at different initial concentrations of Cr (VI) from 200 to 1 000 mg/L, were studied. The most removal of metal, was eight days, with 100 and 79 %, for both biomasses, modified and not modified, respectively, at 28 °C, pH 1.0, and 1 g of biomass. Concerning the incubation temperature, the highest removal was at 60 °C, with 100 % of removal after five days. Additionally, the biomass concentration does influence the metal removal, and efficiently remove the metal from contaminated earth and wastewater (71 and 73 %, respectively), after 10 days of incubation with 10 g of biomass. Se estudió la capacidad de remoción de cromo (VI) en solución acuosa por la biomasa modificada del grano de arroz, utilizando el método colorimétrico de la difenilcarbazida, para evaluar la concentración del metal. Se evaluó la bioadsorción a diferentes pH´s (1, 2, 3 y 4) a diferentes tiempos. También se estudió el efecto de la temperatura en el intervalo de 28 a 60 °C y la remoción a diferentes concentraciones iniciales de Cr (VI) de 200 a 1 000 mg/l. La mayor remoción del metal fue a los ocho días, con un 100 y 79 %, para las biomasas modificada y no modificada, respectivamente, con un pH de 1.0, 28 °C y 1 g de biomasa. Con respecto a la temperatura de trabajo, la óptima fue de 60 °C, con un 100 % de remoción a los cinco días, mientras que a las concentraciones de cromo (VI) analizadas, la biomasa natural mostró una buena capacidad de remoción, eliminando 200 mg/l del metal a los 13 días y una temperatura de 28 °C. Además, a mayor concentración de la biomasa, es mayor la remoción del metal, y elimina eficientemente el metal de tierra y aguas residuales contaminadas (71 y 73 %, respectivamente), a los 10 días de incubación con 10 g de biomasa modificada.