**1. Introduction**

Nowadays, one of the most important environmental issues is related to water scarcity, water contamination and water quality. In many cases, water contamination is due to pollution by means of the presence of inorganic and/or organic compounds; particularly, the presence of organic dyes in waters, or in general, in effluents must be avoided since they are toxic (mutagenic, i.e. Azure B or Disperse Red 1, and carcinogenic, i.e. Basic Red 9 and Crystal Violet) against life and humans. Under the word "dye," is included substances which.

produced a color on materials of diverse nature, being the textile industry (54%) which produced the highest quantity of dyes-bearing effluents, followed by the dyeing industry (21%), paper and pulp industry (10%), tannery and paint industry (8%) and the own dye manufacturing industry (7%).

These compounds can be classified on structural bases, i.e. basic, acid, azo, disperse, anthraquinone or metal complex. The international standard of dye effluent discharge into the environment considered the next tolerable limits [1]: i) biological oxygen demand: under 30 mg/L, ii) chemical oxygen demand: below 50 mg/L, iii). color: under 1 ppm; .iv) pH value in the 6–9 range, v) suspended solids: less than 20 mg/L, vi) temperature: below 42° C, and vii) toxic pollutants: completely avoid. However and despite all prohibitions, still today there is an important number of illegal dyes (i.e. Solvent Yellow 4, a member of the azolipophilic compounds) used in the textile industry. There are a number of useful technologies to eliminate these organic dyes from waters-effluents [2, 3], and among them, adsorption processes gained a paramount interest due to their manipulation easiness, scaling up, and the possibility of using a countless number of potential adsorbents.

The present work, and due to space constrains, reviewed the most recent results (January–April 2020) about the removal of organic dyes by adsorption processes.
