The aim of this study was to investigate the effectiveness of B doped TiO2 on the removal of metoprolol tartrate salt (MET) in ultrapure water (UW) and municipal secondary effluent (SE) using a Xenon lamp (photon flux of 2.99 x 10(-6) Einstein s(-1)) as irradiation source. The analyzed parameters were MET removal, total organic carbon (TOC), chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and acute toxicity (Microtox (R)). The optimal photocatalyst concentration was determined in both matrices. After 180 min of irradiation, 70% and 44% of MET were removed using 0.4 g L-1 catalyst in UW and 2.0 g L-1 catalyst in SE, respectively. A substantial improvement of biodegradability (BOD5/COD) was also achieved. The acute eco-toxicity decreased when MET was degraded and no toxic products were formed at the end of the process. Several reaction intermediates generated during the MET removal were identified and a possible degradation pathway was proposed for the TiO2/5%B(w/w) reaction. Photocatalysis with B-doped TiO2 can be considered as an interesting MET degradation alternative, leading to higher removals and potential to use solar energy, thus, minimizing the operating costs. (C) 2015 Elsevier B.V. All rights reserved.