Efficient sorption performance of carbon-diatomaceous silica compounds towards phenol

Abstract

Phenol removal as organic pollutant model has been studied on new composite adsorbents prepared from carbon and natural diatomaceous silica mixtures in different proportions (KCp1, KCp2, and KCp3 with 10, 20, and 30% of carbonaceous matter, respectively). SEM observations clearly showed the porous aspect evolution when mixing carbon with the macroporous diatomite skeleton, further proved by TEM images that revealed a co-existence of two distinct pore sizes. FTIR and XRD characterization mainly demonstrated the disappearance of calcium carbonate species as consequence of the undertaken treatments in presence of carbon. N2 sorption analysis at 77 K confirmed the obtaining of more developed textural properties with enhanced BET surfaces, and the creation of narrower porosity. The best area was obtained for KCp3 (336 m2/g) as compared to the starting carbon and diatomite surfaces (118 and 8 m2/g, respectively). The influence of several parameters such as contact time, temperature, pH, and initial concentration on the performance of the resultant materials in terms of phenol adsorption was investigated. The pH ≤ 8 favored the phenol removal, whereas the temperature did not have a great impact in the selected range (30-60°C). The sorption isotherms followed well the Freundlich and, more accurately, Langmuir models with the highest adsorption capacity recorded for KCp3 (98.5 mg.g−1). A fast kinetic was revealed whose data best fitted with the pseudo-second-order model with a correlation factors values of R2=0.996, 0.999, and 0.992 for KCp1, KCp2, and KCp3 respectively. More than 50% of the maximum adsorption ratio was achieved in half the time needed for saturation. The new composites offer promising prospects as inexpensive sorbents for use with competitive capacities in the industrial water treatment.