Activated carbon (AC) being a high-quality adsorbent can be produced from agricultural wastes that are economical in comparison to several carbonaceous raw materials and commercially available carbons for water purification. Here, AC was produced from washed, sun and oven dried spent tea after digestion with 0.5M and 1 M potassium acetate used as an activating agent, direct combustion, and carbonization in muffle furnace at 500oC. Later, the sorbent was sieved through 250µm and 560µm mesh sizes and was characterized for pH, ash content, iodine number, moisture content, and percentage yield. The effect of sorbent size, sorbent dosages and contact time on adsorption ability of AC to remove methylene blue (cationic dye) and reactive red 120 (anionic dye) from textile industrial effluent was studied. The maximum yield was 31.41% from 100g of the bio-sorbent. Maximum adsorption ability of activated carbon produced from 1M treated spent tea relates with high iodine number, 422.8mg/g. The AC with alkaline pH led to higher percentage removal of cationic dye (99.71%) as compared to the anionic dye (38.57%) at sorbent dose (0.3g/ml), sorbent size (250µm) and contact time (2.5h). The current findings helped in understanding the efficacy of AC at two wavelengths, 668nm and 536nm for methylene blue and reactive red, respectively for dye removal from industrial wastes. Additionally, this cost-effective method can be utilized on large scale to treat wastewater and lessen the environmental pollution to a safe extent.