Removal of Methylene Blue, Chromium (VI), and Phenol from Water via Steam-Activated Coconut Endocarp Carbon in a Semi-Industrial Kiln

The carbonization and steam activation of coconut (Cocos nucifera) endocarp, in a semi-industrial kiln, was carried out to obtain Activated Coconut Endocarp Carbon (AC-EC) and to evaluate its adsorption capacity for methylene blue (MB), chromium (Cr (VI)), and phenol (PHN). The optimum conditions for production were reached at carbonization temperatures of 500 oC for 60 min followed by activation at 800 oC for another 60 min, using water vapor. These conditions provided an surface area of 712.371 m(2) g(-1) for AC-EC and removal efficiency of PHN, MB, and Cr (VI) pollutants of 96.08%, 93.16%, and 19.64%, respectively, at equilibrium time. The AC-EC showed a yield of 14.83%, ash content of 2.19%, bulk density of 0.59 g cm(-3), and total pore volume of 0.347 cm(3) g(-1), predominantly microporous. Batch adsorption studies were carried out at different initial MB, Cr (VI), and PHN concentrations (25-1000 mg L-1), contact time (0-48 h), and room temperature (25 +/- 2 degrees C). The adsorption process was favorable (0 < R-L < 1) and the maximum adsorption capacity (q(m)) was 302.19 mg g(-1), 30.00 mg g(-1), and 184.11 mg g(-1) for MB, Cr (VI), and PHN, respectively. The Langmuir isotherm fitted well to the MB equilibrium data, and the Freundlich isotherm to the Cr (VI) and PHN equilibrium data. The adsorption kinetics for MB follow the pseudo-first-order model and Cr (VI) and PHN follow the pseudo-second-order model. The results showed the quality of AC-EC, obtained in a semi-industrial kiln, as a promising adsorbent for removing pollutants from an aqueous medium.

Automated summary

The carbonization and steam activation of coconut endocarp were conducted to obtain Activated Coconut Endocarp Carbon (AC-EC) with high adsorption capacity for methylene blue (MB), chromium (Cr (VI)), and phenol (PHN). Optimal production conditions were achieved at carbonization temperature of 500 °C for 60 min followed by activation at 800 °C for another 60 min. The AC-EC demonstrated a large surface area, high removal efficiency for pollutants, and favorable adsorption kinetics.