The inappropriate release of pharmacological residues in different environmental compartments has brought great concern in different parts of the world, since drugs and their metabolites can generate adverse risks to the ecosystem and the health of human beings. Therefore, several researches have been developed with the purpose of using remediation methods to remove these emerging contaminants from the environmental matrices. Thus, this study aims to understand the physical and chemical aspects that are involved in the removal of sodium cromoglycate (CG) and sodium diclofenac (DF) drugs in aqueous solution by the adsorption process using cross-linked chitosan as adsorbent, as well as to develop through an algorithm, a simple and reliable method to quantify binary mixtures of drugs in aqueous solutions. Samples of chitosan cross-linked (QR) with glutaraldehyde and the others submitted to the adsorption process were characterized by infrared absorption spectroscopy, X-ray diffraction and zeta potential. Regarding the study of the adsorption equilibrium, they were carried out at four different temperatures (15°C, 25°C, 35°C and 45°C) with the aid of a UV-Vis spectrophotometer. Then, to estimate the parameters of the adsorption isotherms, the experimental data were fitted to the following adsorption isotherms: Henry, Langmuir, Freundlich, Sips and Redlich-Peterson. For the quantification of drug mixtures in solution, multiple measurements by UV-Vis spectrophotometry were used. This procedure aimed to create calibration curves for a given drug, with apparent molar absorptivity as a function of the concentration of a second drug, which were used to determine drug concentrations in solutions of two drugs, specifically GC and DF. Then, the relative errors were estimated from exponential-type functions, asymptotically decreasing to its lowest value as the concentration increases. The results revealed that the crosslinking process was successful and that its surface was negative. Furthermore, it was observed that there was no significant change when comparing the QR spectra before and after the sorption process with anionic drugs. Therefore, it is clear that, probably, the drugs were adsorbed only on the surface of the polymer. With regard to balance studies, the Sips model was the one that presented the highest coefficient of determination ( R2 >0.95). Therefore, it was chosen and presented as the best mathematical model to explain the experimental data. The values of thermodynamic constants revealed that the adsorption of drugs is endothermic in nature, favored by increasing temperature. As for pharmaceutical residues, the algorithm developed in the study presented adequate validation, as the experimental concentration values were statistically similar to the values calculated by the developed method. Therefore, the adsorbent used in this research can be proposed as another alternative to be applied in the remediation of drugs in effluents, because these materials have adsorption capacity, low toxicity and are biodegradable.