Removal of furfural in wastewater by Al-MIL-53 prepared in various solvents

Acid insoluble lignin material production by chemical activation of olive endocarps for an efficient furfural adsorption-removal from aqueous solutions

The present work describes a protocol of chemical activation, with acid catalyst, of olive endocarps to obtain acid insoluble lignin-rich materials with high capacities for the adsorption of furfural present in aqueous media. During biomass activation, factors such as acid concentration, reaction time and temperature, solid/liquid ratio and the presence of water extractives strongly affected both the surface characteristics of the treated bioadsorbents and their capacities for furfural retention (percentage increase close to 600% with respect to the crude biomass). Once a treated solid with good adsorbent properties was obtained, the optimal conditions for adsorption were found: stirring speed 80 rpm, temperature 303 K and adsorbent load 7.5 g solid/50 cm3. Kinetic study indicated the pseudo-second order model provided the best fit of the experimental data. At 303 K, the equilibrium adsorption capacities values ranged from 2.27 mg g-1 to 29.29 mg g-1, for initial furfural concentrations between 0.49 g dm-3 and 12.88 g dm-3. Freundlich model presented the best isotherm (R2 = 0.996 and SE = 4.7%) providing KF and n values of 0.115 (mg g-1) (mg dm-3)-n and 0.610, respectively. Since physical interactions predominate in the adsorption of furfural on chemically activated olive endocarps, the furfural removal process could have occurred reversibly on the heterogeneous surface of the bioadsorbents.

A dual purpose aluminum-based metal organic framework for the removal of chloramphenicol from wastewater

The presence of antibiotics in the aquatic environment can cause significant environmental and human health problems even at trace concentrations. Conventional treatment systems alone are ineffective in removing these resistant antibiotics. To address this problem, oxidation and adsorption techniques were used to explore the removal of recalcitrant antibiotic chloramphenicol (CAP). An aluminum-based metal-organic framework (Al-MIL) with high surface area and extended porosity, was prepared and used both as adsorbent and catalyst for the oxidation of CAP. Characterization of the Al-MIL revealed a large surface area of 1137 m² g^-1, a homogeneous microporous structure, good crystallinity, and particle size in the range of 200-400 nm. Adsorption of CAP on Al-MIL achieved equilibrium after 1 h, reaching a maximum adsorption capacity of 96.1 mg g^-1 at the optimum pH value of 5.3. The combination of adsorption and oxidation did not improve the % TOC reduction considerably, indicating an antagonistic rather than synergistic effect between the two processes. Oxidation alone in the presence of persulfate, achieved a % TOC reduction of 71% after 2 h, compared to 56% achieved by adsorption alone at the same duration. The optimum persulfate concentration was determined as 2.5 mM. The Al-MIL structure did not demonstrate any substantial deterioriation after six repeated runs, according to the reusability experiments.