Abstract
This is the first study examining pharmaceutical removal under anoxic conditions with MnO2. This study compares the abiotic removal of seven pharmaceuticals with reactive MnO2 particles in the presence of oxygen (oxic conditions) and in the absence of oxygen (anoxic conditions). Due to the novelty of pharmaceutical removal under anoxic conditions, the influence of phosphate buffer, pH, and MnO2 morphologies is also examined. Results show that over 90% of diclofenac is removed under anoxic conditions. Additionally, we found that (1) anoxic conditions are beneficial for diclofenac removal with MnO2, (2) phosphate buffer affects the pharmaceutical removal efficiencies, (3) higher pharmaceutical removal is obtained at acidic pH compared to that at neutral or alkaline conditions, and (4) amorphous MnO2 removes pharmaceuticals better than crystalline MnO2. The pharmaceutical molecular structure and properties, MnO2 properties especially reactive sites of the MnO2 surface, are important for degradation kinetics. This study provides a fundamental basis towards understanding pharmaceutical degradation with MnO2 under anoxic conditions, and development of a cost-effective, sustainable technology for removal of pharmaceuticals from water.
Highlights
Pharmaceuticals in the water cycle threaten the aquatic environment and drinking water resources
The results show that removal efficiency of diclofenac is higher under anoxic conditions, while higher removal is observed under oxic conditions for metoprolol and propranolol
Diclofenac removal efficiencies of 78% under anoxic conditions and 59% under oxic conditions were observed after 24 h, incubating a solution of mixed pharmaceuticals in demineralized water (Fig. 1a)
Summary
Pharmaceuticals in the water cycle threaten the aquatic environment and drinking water resources. Removal of many pharmaceuticals such as carbamazepine, diclofenac, or metoprolol is poor in conventional wastewater treatment processes, such as activated sludge processes, due to the low biodegradability and limited sorption properties of many pharmaceuticals (Vieno and Sillanpaa 2014). Advanced technologies such as ozonation or photodegradation successfully remove selected pharmaceuticals from water and wastewater (He et al 2016; Javier Benitez et al 2009). These technologies require more energy inputs and operational costs, in addition to often high construction and maintenance costs, and produce intermediate compounds with unknown environmental effects
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