The density functional theory framework is used to study geometry and electronic properties of pristine tricycle arsenene nanoribbon (T-AsNR) and Ga substituted T-AsNR. The stable geometry of both T-AsNR is ensured based on the formation energies. The obtained formation energies for T-AsNR and Ga-substituted T-AsNR are −4.462 and −4.512 eV/atom, respectively. Also, the band gap is calculated to be 0.635 and 0.212 eV, respectively for pristine and Ga substituted T-AsNR, which are semiconductors. Furthermore, T-AsNR is used as a base substrate to adsorb sulfisoxazole in the aqueous medium. Moreover, the adsorption of sulfisoxazole on both T-AsNR possesses chemisorption. Besides, the adsorption energy at the valley site of T-AsNR and Ga-substituted T-AsNR are −6.313 eV and −6.346 eV. The average energy gap variation for Ga-substituted T-AsNR was highest at the top site and is about 174.06%, whereas the pristine one showed 6.93 %. The change in the electronic properties of T-AsNR is observed with regard to band structure, electron density, and density of states spectrum. Thus, the outcome suggests that T-AsNR is a prominent adsorbing medium of sulfisoxazole in contaminated water.