Analysis of sulfamethoxazole and trimethoprim adsorption on sewage sludge and fish waste derived adsorbents

• Sewage sludge/fish waste adsorbents were used for the removal of pharmaceuticals.
• Adsorption of trimethoprim was 41% higher than that of sulfamethoxazole.
• Adsorption capacity is governed by complex surface chemistry.
• Chelation of trimethoprim with metal cations takes place.
• Sulfamethoxazole is adsorbed via acid-base interactions with an inorganic phase.

Sewage sludge, fish waste, and mixtures of the two were pyrolized at 650 and 950 °C in order to convert them into stable adsorbents. To test their performance in the removal of pharmaceuticals from water, sulfamethoxazole (SMX) and trimethoprim (TMP) were chosen as model adsorbates. Adsorption isotherms were measured in batch adsorption tests at room temperature. The adsorbents prepared at 950 °C were more effective than those obtained at 650 °C. Even though both pharmaceuticals were adsorbed in the highest amount on the material composed of pyrolized fish waste, for TMP removal the composite obtained from 90% sewage sludge and 10% fish waste was equally effective. To elucidate the adsorption mechanism, detailed surface analyses by TA-MS, XRD and potentiometric titration were carried out. Favorable surface chemistry seems to be the factor governing the performance of these adsorbents as media for the pharmaceuticals' removal from an aqueous phase. The main adsorption mechanism is based on chelation, acid-base interactions and polar interactions with the inorganic phase.

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