Enhancing Photocatalytic Efficiency of Spent Tea Leaf Powder on ZnIn₂S₄ Incorporation: Role of Surface Charge on Dye Degradation

Abstract

Photocatalytic degradation of dye contaminants using nanocomposite adsorbents has emerged as a promising solution for wastewater treatment. Owing to its abundant availability, eco-friendly composition, biocompatibility, and strong adsorption activity, spent tea leaf (STL) powder has been extensively explored as a viable dye-adsorbent material. In this work, we report spectacular enhancement in the dye-degradation properties of STL powder on incorporation of ZnIn2S4 (ZIS). The STL/ZIS composite was synthesized using a novel, benign, and scalable aqueous chemical solution method. Comparative degradation and reaction kinetics studies were performed onto an anionic dye, Congo red (CR), and two cationic dyes, Methylene blue (MB) and Crystal violet (CV). The degradation efficiencies of CR, MB, and CV dyes were obtained to be 77.18, 91.29, and 85.36%, respectively, using the STL/ZIS (30%) composite sample after the 120 min experiment. The spectacular improvement in the degradation efficiency of the composite was attributed to its slower charge transfer resistance (as concluded by the EIS study) and optimized surface charge (as concluded by ζ potential study). Scavenger tests and reusability tests deciphered the active species (•O2 –) and reusability of the composite samples, respectively. To the best of our knowledge, this is the first report to demonstrate improvement in the degradation efficiency of STL powder on ZIS incorporation.

The Bioactive Substances in Spent Black Tea and Arabic Coffee Could Improve the Nutritional Value and Extend the Shelf Life of Sponge Cake after Fortification

“…Currently, the awareness of the general farmers and consumers of terms including sustainable development and circular bioeconomy helped in mitigating this problem, and agri-food waste is now accepted as a valuable resource and re-entered the supply chain via recycling, valorization, energy recovery, and other uses. ,− In this context, there have been studies on the use of used spent coffee and tea leaves in the field of livestock nutrition, agricultural compost, or production of biogas, or valorized for their bioactive molecules. ,,− However, there is a lack of research on the use of spent tea and coffee in the production of novel foods. − …”