*Article* **Removal of Reactive Black 5** *Dye* **by Banana Peel Biochar and Evaluation of Its Phytotoxicity on Tomato**

**Riti Thapar Kapoor <sup>1</sup> , Mohd Rafatullah 2,\* , Masoom Raza Siddiqui <sup>3</sup> , Moonis Ali Khan <sup>3</sup> and Mika Sillanpää <sup>4</sup>**


**Abstract:** Removal of Reactive Black 5 (*RB*5) *dye* from an aqueous solution was studied by its adsorption on banana peel biochars (BPBs). The factors affecting *RB*5 *dye* adsorption such as pH, exposure time, *RB*5 *dye* concentration, adsorbent dose, particle size and temperature were investigated. Maximum 97% *RB*5 *dye* removal was obtained at pH 3 with 75 mg/L adsorbate concentration by banana peel biochars. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent material. The data of equilibrium were analyzed by Langmuir and Freundlich isotherm models. The experimental results were best reflected by Langmuir isotherm with maximum 7.58 mg/g adsorption capacity. Kinetic parameters were explored and pseudo-second order was found suitable which reflected that rate of adsorption was controlled by physisorption. Thermodynamic variables exhibited that the sorption process was feasible, spontaneous, and exothermic in nature. Banana peel biochar showed excellent regeneration efficiency up to five cycles of successive adsorption-desorption. Banana peel biochar maintained >38% sorption potential of *RB*5 *dye* even after five cycles of adsorption-desorption. The phytotoxic study exhibited the benign nature of BPB-treated *RB*5 *dye* on tomato seeds.

**Keywords:** banana peel biochar; reactive black 5; isotherm; kinetic; phytotoxicity; tomato
