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The polypyrrole (PPy) was used as an adsorbent material for efficient removal of pharmaceutical metronidazole from aqueous solutions. The physiochemical parameters influencing the adsorption process such as adsorbent dose, temperature, pH, initial concentration and contact time were systematically investigated. The optimum adsorption efficiency is achieved at pH 6.17 after 120 min of contact time. In addition, the Langmuir isotherm and pseudo-second-order models were found to explain the metronidazole adsorption process on the PPy. The thermodynamic parameters indicate that the adsorption of metronidazole on the PPy is a spontaneous and exothermic process. The quantum calculations using density functional theory (DFT) was used to confirm the adsorption mechanism of metronidazole on the PPy. The obtained results of the interaction energy indicate that the adsorption was a physical process. The metronidazole was adsorbed by its oxygen atoms on the amine groups of PPy. Finally, the PPy polymer can be used as an efficient adsorbent for removal of pharmaceutical pollutants from wastewater.

Adsorbents in the form of powders are commonly used to filtrate organic compounds in waters. However, this technique requires the separation of the solid phase from the solution after adsorption experiments. Here we propose the use of films as adsorbents. We synthesized polyaniline films by chemical oxidative polymerization of aniline on red ceramic brick. This film was tested to remove trimellitic, hemimellitic and pyromellitic acids as model molecules of the biodegradation of aquatic humic substances. We evaluated the effect of pH, contact time and initial concentration. Our results show that optimal adsorption conditions required 45 min of solid/liquid contact at pH 7 and an initial concentration of 20 mg/l. The maximum adsorption capacities for hemimellitic, trimellitic and pyromellitic acids are 154.83 for hemimellitic acid, 161.88 for trimellitic acid and 175.26 mg/g for pyromellitic acid. The adsorption efficiency of the polyaniline film decreased only by 13 % after four cycles. Overall, we conclude that polyaniline films are promising separable adsorbents compared to conventional adsorbents for removal of aromatic polycarboxylic acids from water.

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This study reports the application of Spruce wood sawdust as a low-cost and eco-friendly adsorbent for the removal of sodium salicylate from aqueous solutions. The effects of physicochemical parameters on the sodium salicylate adsorption process such as initial pH, temperature, solid/liquid ratio, initial concentration, contact time, and ionic strength were investigated. The optimum adsorption conditions were found as: equilibrium time = 3h, adsorbent dosage = 0.5 g/L, pH= 6.5, initial sodium salicylate concentration = 10 mg/L and temperature = 25°C. The kinetic study shows that the pseudo-second-order model is suitable to describe the adsorption process. The adsorption isotherm models (Langmuir, Freundlich, Temkin and generalized) were tested to understand the adsorption mechanism of sodium salicylate onto wood sawdust surface. The adsorption of sodium salicylate follows the Langmuir isotherm model. The maximum monolayer uptake capacity was found to be 99.01 mg/g. In addition, the temperature seems to have no noticeable effect on the adsorption of sodium salicylate. Finally, the thermodynamic parameters indicate that the adsorption is spontaneous (ΔG°˂ 0) and exothermic (ΔH°=-5.081 kJ/mol) in nature. Overall, Spruce wood sawdust can be used as a cost-effective and eco-friendly adsorbent for wastewater treatment applications.