The discharge of large amounts of effluents contaminated with gentian violet (GV) and phenol red (PR) threatens aquatic flora and fauna as well as human health, which is why these effluents must be treated before being discarded. This study seeks the removal of dyes, using water lily (Eichhornia crassipes) as an adsorbent with different pretreatments. PR and GV were analyzed by a UV-visible spectrophotometer. Equilibrium experimental data showed that Freundlich is the best model to fit PR and SIPS for GV, showing that the adsorption process for both dyes was heterogeneous, favorable, chemical (for GV), and physical (for PR). The thermodynamic analysis for the adsorption process of both dyes depends directly on the increase in temperature and is carried out spontaneously. The Pseudo first Order (PFO) kinetic model for GV and PR is the best fit for the dyes having an adsorption capacity of 91 and 198 mg/g, respectively. The characterization of the materials demonstrated significant changes in the bands of lignin, cellulose, and hemicellulose, which indicates that the functional groups could participate in the capture of the dyes together with the electrostatic forces of the medium, from which it be concluded that the adsorption process is carried out by several mechanisms.

Bioremediation is a pollutant removal method that has had a great boom due to the diversity of agroindustrial waste that can be used for this purpose, and that has shown having great efficiency and profitability in the adsorption of heavy metals, such as Pb, Cu, and Co. Based on the above, the present work carried out kinetic and equilibrium studies of bioadsorption of Cr (III) using orange peel (OP) as adsorbent, previously treated with methanol, water, and a water–methanol mixture at different pH (0.91, 1.78 and 2.72), and at 30 °C, finding that the adsorption capacity at equilibrium increases with increasing pH, having a maximum of 55 mg g⁻¹ at pH 2.72—under these conditions, lower adsorption energy was used to remove Cr (III). In addition, it was determined that there are no external mass transfer limitations. An isoelectric point analysis indicated that the adsorption is not carried out by electrostatic forces and a FTIR study of the functional groups of OP showed a decrease in the main functional groups (pectin, cellulose, and lignin, among others), which is directly related to the adsorption capacity of the bioadsorbent.

Phytoremediation consists of taking advantage of the capacity of certain plants to absorb, accumulate, or metabolize contaminants. In this study, Eichornia crassipes (water lily) treated with water (WLW) and NaOH (WLN) was investigated as an adsorbent for removal of Ni(II) and Cu(II) present in aqueous solution, focusing on determining the most efficient conditions (adsorbent concentration, contact time, pretreatment, temperature). The results showed that equilibrium adsorption was favorable and carried out by a multilayer physical process with both bioadsorbents. The maximum adsorption at 30 °C in WLW and WLN was 349 and 293.8 mg/g of Ni(II), respectively, and 294.1 and 276.3 mg/g of Cu(II), respectively. The thermodynamic analysis indicated that the removal in both metals was spontaneous and exothermic. The Avrami model was the most adequate in the kinetic study of Ni(II) and Cu(II) removal in both treatments, which revealed that the adsorption process was carried out by several mechanisms. In the characterization of the adsorbents, it was determined that the functional groups of WL as well as the attractive forces on the surface of the materials participated in the metal removal process.

The textile industry is very important because its products are widely used by society, however, this activity has a great contribution to the contamination of water resources due to its effluents that contain large amounts of colorants, among which is the blue of methylene (MB) and methyl orange...