The aim of this study was to produce high quality activated carbons from Diplotaxis harra biomass by potassium hydroxide
activation and their application in heavy metals removal. To reduce the number of experiments, full factorial experimental design
at two levels (24) was carried out to occur optimal preparation conditions for efficient removal of cadmium and cobalt ions from
aqueous solutions. Different variables influencing activation process, such as carbonization temperature (500–600°C), activation
temperature (400–500°C), activation time (1–2h) and impregnation ratio (g KOH/g carbon) (1–2) have been investigated and the
best production conditions were determined. The experimental results showed that the carbonization temperature was the most
significant factor that influences the iodine number of the activated carbons. The methylene blue index was more influenced by the
activation temperature. The removal of cadmium and cobalt ions by activated carbons was more sensitive to methylene blue index
instead of iodine number. Although, the removal of the both heavy metals is more influenced by activation temperature with a
negative effect followed by the impregnation ratio with a positive impact. Based to the statistical data, the best conditions for the
removal of cadmium and cobalt by the prepared activated carbons have been established. The maximum iodine number and
methylene blue index obtained under these conditions were 696.84 mg/g and 235.64 mg/g respectively. The sorption capacities of
optimized activated carbons were determined by isotherm study. The maximum capacities obtained with the application of the
Langmuir model were 118.09 mg/g for cadmium sorption onto AC carbonized at 600°C, activated at 400°C during 1h with an
impregnation ratio of 2 g/g, and 48.89 mg/g for cobalt sorption onto and AC carbonized at 600°C, activated at 500°C during 1h
with an impregnation ratio of 2g/g respectively. These sorption capacities were greater than those of a commercial activated carbon
used in water treatment.