Remoción del plomo (Pb) en muestras de agua del río Tumbes utilizando un material adsorbente a base de sillar (ignimbrita)

Tumbes River is the main source of water for the city of the same name in northwest Peru. However, under current conditions it is negatively affected by activities such as artisanal mining in the upper part of the basin. It causes water pollution with heavy metals such as lead, which is potentially a cause of chronic diseases. On the other hand, ignimbrite is a volcanic rock extracted in the city of Arequipa. It is used as construction material and when it is cut into blocks, produces residual material that is normally discarded. This research aimed to produce and characterize adsorbent materials based on ignimbrite to directly remove Pb from the water of the Tumbes River. The ignimbrite was used in particle sizes of 150 µm and 250 µm, and the materials were activated by slow pyrolysis with and without the presence of ZnCl2. Then thermal treatment, the materials were impregnated with ZnO nanoparticles (NPs) using the in-situ impregnation technique. The thermal treatment manages to modify the structure of the materials, increasing their crystalline phase; however, apparently the concentration of ZnO NPs impregnated on the pyrolyzed ignimbrite samples was too low to be detected by X-ray diffraction. In the Pb adsorption kinetic tests using water samples directly from the Tumbes River, it is shown that adsorbents based on ignimbrite showed limited adsorption capacity compared to other adsorbents derived from rocks, obtaining adsorption values between 0.009 – 0.017 mg of Pb/g of the adsorbent. However, the final concentrations after the adsorption experiments were below the limit of 0.05 mg/l established by the WHO for drinking water. Despite this, it is important to conducted experiments using other types of ignimbrite and other types of modifications to corroborate the potential use of ignimbrite as an adsorbent.