Theoretical interpretation of the adsorption of amoxicillin on activated carbon via physical model.

The paper describes a theoretical analysis of the adsorption of amoxicillin (AMX) onto two activated carbons pyrolysed at either 600 or 700 °C (PAC-600 and PAC-700). Series of experimental data are carried out at different temperatures ranging from 10 to 45 °C, as this is the first key factor to explain the adsorption mechanism of this pollutant. AMX adsorption capacity varied from 275 to 450 mg/g and between 276 and 454 mg/g for PAC-600 and PAC-700, respectively. It can be deduced that the pyrolysis temperature does not play a crucial role in AMX removal capacity of the adsorbents. A comparison with literature data shows that the retrieved adsorption capacities of both the adsorbents are very competitive for an effective water treatment. Physical models are applied to the two experimental data sets showing that a monolayer model with single energy is the best option to explain the AMX adsorption mechanism on both PAC-600 and PAC-700 adsorbents. The interpretation of the theoretical results points out that the AMX was not aggregated during the adsorption process. Under these experimental working conditions, it is noted that AMX is adsorbed almost via a parallel orientation on PAC-600 and PAC-700 adsorbents, reflecting that the adsorption is a multi-interaction mechanism. The model provides an estimation of the adsorption energy that allows the quantification of the interactions between the AMX and both PAC-600 and PAC-700 adsorbent surfaces; in both the cases, physical bindings are involved in AMX adsorption.

Removal of pharmaceutical compounds from aqueous solution by novel activated carbon synthesized from lovegrass (Poaceae).

In this work, lovegrass (Cpa), an abundant grass of the Poaceae family, was employed as feedstock for the production of activated carbon in a conventional furnace using ZnCl2 as a chemical activator. The prepared material (Cpa-AC) was characterized by pH of the point of zero charges (pHpzc), Boehm's titration method, CHN/O elemental analysis, ATR-FTIR, N2 adsorption/desorption curves, and SEM. This carbon material was used for adsorption of acetylsalicylic acid (ASA) and sodium diclofenac (DFC). FTIR analysis identified the presence of O-H, N-H, O-C=O), C-O, and aromatic ring bulk and surface of (Cpa-AC) adsorbent. The quantification of the surface functional groups showed the presence of a large amount of acidic functional groups on the surface of the carbon material. The isotherms of adsorption and desorption of N2 confirm that the Cpa-AC adsorbent is mesopore material with a large surface area of 1040 m2 g-1. SEM results showed that the surface of Cpa-AC is rugous. The kinetic study indicates that the system followed the pseudo-second-order model (pH 4.0). The equilibrium time was achieved at 45 (ASA) and 60 min (DCF). The Liu isotherm model best fitted the experimental data. The maxima sorption capacities (Qmax) for ASA and DFC at 25 °C were 221.7 mg g-1 and 312.4 mg g-1, respectively. The primary mechanism of ASA and DFC adsorption was justified considering electrostatic interactions and π-π interactions between the Cpa-AC and the adsorbate from the solution.

Conversion of Eragrostis plana Nees leaves to activated carbon by microwave-assisted pyrolysis for the removal of organic emerging contaminants from aqueous solutions.

Eragrostis plana Nees leaves, abundant lignocellulosic biomass, was used as carbon source for preparation of activated carbon, by using microwave-assisted pyrolysis and chemical activation. The novel activated carbon (MWEPN) was characterised by FTIR, CHN elemental analysis, Boehm's titration method, TGA, SEM, N2 adsorption/desorption curves and pH of the point of zero charge (pHpzc). Afterwards, the adsorbent was successfully employed for adsorption of the two emerging contaminants (caffeine and 2-nitrophenol). The results indicated that MWEPN had a predominantly mesoporous structure with a high surface area of 1250 m2 g-1. FTIR analysis indicated the presence of carbonyl, hydroxyl and carboxylic groups on the surface of MWEPN. The Boehm analysis showed the existence of the high amount of acid moieties on the surface of activated carbon. Adsorption kinetic indicated that the system followed the Avrami fractional order at the optimal pH of 7. The equilibrium time was attained at 30 min. The Liu isotherm model better described the isothermal data. Based on the Liu isotherm, the maximum sorption capacities (Qmax) of caffeine and 2-nitrophenol adsorbed onto activated carbon at 25 °C were 235.5 and 255.8 mg g-1, respectively.