Effect of the pH and the Catalyst Concentration on the Removal of Hexavalent Chromium (Cr (VI)) During Photocatalysis of Wastewater from Plating on Plastics Industry

Abstract

The advancement of industrial technologies throughout history has allowed human beings to develop a great diversity of sectors and methods to satisfy their growing needs. However, various sectors use environmentally unfriendly technologies and have become a significant problem. Those sectors who use heavy metals such as mercury, nickel, cadmium, lead, chromium, among others, stand out. The hexavalent chromium (Cr (VI)) is a long-term environmental pollutant in wastewater generated in electroplating, printing, dyeing, painting, battery manufacturing, metal processing, tanning, and other industries. Chromium poisoning causes cancer, lung, and liver damage due to its multiple toxicities, so it is essential to eliminate Cr (VI) from urban and industrial wastewater before releasing it into the environment. The removal of Cr (VI) from wastewater includes various methods such as membrane separation, precipitation, adsorption, and photocatalysis. Photocatalysis is a low cost, environmentally-friendly, and efficient alternative for the removal of Cr (VI).
The present research work proposes determining the effect of catalyst concentration and pH in removing Cr (VI) through tertiary wastewater treatment known as heterogeneous photocatalysis and using titanium dioxide (TiO₂) as a catalyst. Different amounts of wastewater samples from the plating on plastics industry were collected for this study. The industry is in Bogota, Colombia. The experimental campaign was carried out on a laboratory scale, radiating the samples using UV lamps. The best conditions for decreasing the pollutant concentration were evaluated through an experimental design. The Cr (VI) concentration level in the samples was monitored using the Test Chromium Kit HI 3846 (Hanna Instruments). The photocatalyst dose and the pH of the samples were the factors evaluated. The results obtained during the work showed that the photocatalytic degradation process is beneficial since removing the pollutant for the wastewater from the plating on plastics industry was up to 98%.