Activated carbon obtained from Opuntia ficus indica by sodium hydroxide activation was employed for the adsorption of p-nitrophenol from water. The activated carbons obtained were characterized by Fourier transforms infrared spectroscopy, sorption of nitrogen, scanning electron microscopy, and Boehm titration. Effects of pH, contact time, amount of adsorbent, and temperature on the adsorption of p-nitrophenol were studied. Adsorption isotherms were analyzed using Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich models, and the thermodynamic parameters have been determined. The adsorption of p-nitrophenol was spontaneous, exothermic, and propitious at 15 ◦C and adopted the pseudo-second order model, and the most credible isotherm was Langmuir’s one. The activated carbon used in this work has good p-nitrophenol adsorption characteristics, and the study of the desorption and reuse of this carbon shows that it retains a removal rate greater than 94% after five cycles of adsorption-desorption.
The adsorption of p-NP on active carbon obtained from Opuntia ficus indica by activation with sodium hydroxide was the subject of this work. The specific surface area of the obtained carbon was 332 m2/g to be used successfully for the retention of p-NP. The adsorption of p-NP on activated carbon is maximal at initial pH = 2, with a removal percentage of 99.3%. The optimum adsorptions parameters were found to be: Adsorbent dose = 6 g/L, Ci = 100 mg/L, temperature = 15 ◦C, and time = 120 min. The kinetics study indicates that the retention of p-NP on the obtained carbon obeys the kinetic model of pseudo-second order. The experimental isotherms are more suitable to the Langmuir model at all temperatures studied. The thermodynamic analysis confirmed that the adsorption of p-NP on active carbon derived from Opuntia ficus indica was spontaneous and exothermic. With increasing temperature, the increase in ∆G◦ values implies that the adsorption of p-NP is favored at low temperature. The desorption and reuse tests of the carbon used in this work have shown that this carbon can be a reusable adsorbent for five adsorption-desorption cycles for the removal of p-NP. Thus, because of its adsorbent properties and the availability of the precursor of this carbon, it can be prepared and used economically for the treatment of waste water polluted by p-NP. Opuntia ficus indica could be considered an interesting and promising source for low-cost preparation of activated carbon as efficient adsorbent for p-NP removal, which represents a good option, especially for the countries without forests.