The objective of this work is therefore, to study the removal of three organophosphate pesticides (diazinon, fenthion and malathion), by their adsorption on waste cellulosic basic. The Waste cellulosic basic was characterized using FTIR, XRD, BET and SEM techniques. The effects of pH, contact time, adsorbent dose, initial concentration, temperature and ionic strength were evaluated and the removal efficiency of each parameter was established. The objective of this work is therefore, to study the removal of three organophosphate pesticides (diazinon, fenthion and malathion), by their adsorption on waste cellulosic basic. The Waste cellulosic basic was characterized using FTIR, XRD, BET and SEM techniques. The effects of pH, contact time, adsorbent dose, initial concentration, temperature and ionic strength were evaluated and the removal efficiency of each parameter was established. OUR WORK INVOLVES ISOTHERMS AND A THERMODYNAMIC STUDY