###### Abstract  
Phenol red (X-PR) and malachite green carbinol (MGC) are two textile finishing dyes, which are present in aquatic environments through industrial effluents. Due to the toxic nature of both dyes, they are harmful to human health. In the present study, two materials, barley seeds and the biochar of barley (_Hordeum vulgare_ L.), were used to remove the dyes in an aqueous solution. The materials used are characterized by AFM, FTIR, SEM, XRD and EDX techniques. In this study, the parameters studied are the adsorbent dose, pH, initial adsorbate concentration and contact time. The maximum equilibrium time was found to be 90 min for all dyes. Kinetic studies revealed that the adsorption of X-PR and MGC on barley seeds (BS-HVL) and the biochar of barley (BC-HVL) followed pseudo-second-order kinetics and that both porous and intraparticle diffusion mechanisms were involved. The adsorption equilibrium data were well fitted to the Langmuir and Freundlich isotherm model for both materials, and the maximum adsorption capacity of monolayer and multilayers for X-PR and MGC were 71.642 mg g\({}^{-1}\) and 50 mg g\({}^{-1}\) on BS-HVL, and 44.843 mg g\({}^{-1}\) and 121.95 mg g\({}^{-1}\) on BC-HVL, respectively. The thermodynamic results reveal that the dye removal on barley was endothermic and spontaneous in nature. barley seeds; biosorbent; isotherm; malachite green; phenol red; ecofriendly adsorbent barley seed extract and its biochar have rarely been proposed for adsorption applications. The aim of this work is to valorize these two materials in order to eliminate two dyes: malachite green and x-phenol red. Natural substances called bioadsorbents (bioproducts) are applicable for water treatment due to the many advantages and interesting properties of these resources. They are abundant, renewable, biodegradable and inexpensive. From a chemical point of view, they contain macromolecular chains with numerous highly reactive chemical functions. Currently, there is an interest in preparing materials based on polysaccharides, and bioadsorption on these bioadsorbents appears to be a promising method [2; 3]. During the last two decades, bioadsorption has proven to be an efficient waste treatment technology [4; 5]. Scientists have successfully removed heavy metals and dyes from wastewater using biosorption [6; 7]. Recently, there is interest in producing materials based on natural substances such as agricultural waste; in this sense, the bioadsorbents appear to be a very promising method for the adsorption of several dyes [8; 9; 10; 11; 12; 13]. Similar research shows that activated carbon derived from the barley (_Hordeum vulgar_ L.) husk can be used as an efficient and cost-effective adsorbent for the treatment of phenol-red-contaminated water. Due to their mutagenic and carcinogenic effects, effluents from the dye, paper and textile industries, contaminated with nondegradable organic dyes, not only pose a serious risk to human health but also adversely affect aquatic life. X-phenol red, a finishing textile dye and a pH indicator, is also used in most tissue culture media. The pH-dependent cytotoxicity of contaminants of phenol red for breast cancer cells has previously been reported by [PERSON] et al. [14]. Malachite green is persistently present in the environment and acutely toxic to a wide range of aquatic and terrestrial animals. Several studies have shown that this dye is highly toxic to freshwater fish, both in acute and chronic exposure. Carcinogenesis, mutagenesis, chromosomal fractures, teratogenicity and reduced fertility have also been reported in rainbow trout following treatment with malachite green [15; 16; 17; 18; 19; 20]. Biomaterials such as barley, due to its microporous structure, high specific surface area and reactivity, play an important role in the adsorption process to remove toxic organic and inorganic chemicals from contaminated water [13]. The aim of this research is to report the synthesis and characterization of barley (_Hordeum vulgar_ L.) seeds and their biochar.