Synthesis of Low-Cost, Bio-Based Novel Adsorbent Material Using Charge-Transfer Interaction for Water Treatment from Several Pollutants: Waste to Worth

Abstract

Tea is the third most consumed beverage in Saudi Arabia (a country in the Middle East) after water and Arabian coffee. Hence, a large amount of consumed tea leaves is discarded as solid waste. Waste tea leaves (WTLs) have no commercial value and could be considered as an environmentally sustainable costless material. This work aimed to manufacture an adsorbent material from the discarded WTLs and charge-transfer (CT) interaction and use this adsorbent material effectively for the removal of different kinds of pollutants from water. The adsorbent material was manufactured in three steps. First, a CrFeO3 metal composite was synthesized from the CT interaction between FeCl3 and CrCl3 with urea. Second, activated carbons were prepared from consumed WTLs using facile and clean treatments of pre-carbonization, and a simple potassium hydroxide (KOH) activation treatment. Finally, the adsorbent material was fabricated by grounding CrFeO3 composite with the activated carbons in a 1:10 molar ratio (metal composite to activated carbons). The prepared materials were characterized spectroscopically and morphologically using FT-IR, XRD, SEM/EDX, and TEM analysis. The synthesized absorbent material was used to adsorb two organic dyes (Azocarmine G2; M1, and Methyl violet 2B; M2), and two commercial pesticides (Tiller 480SL; M3, and Acochem 25% WP; M4) from aqueous solution, and it showed promising adsorption efficacy. The minimum adsorbent material’s dosage to obtain a maximum removal efficiency (R%) for M1, M2, M3, and M4 removal from 100 mL solution (100 mg/L) was 0.11, 0.14, 0.13, and 0.12 g, respectively. The max R% for M1 (96.8%) was achieved in the first 45 min, the max R% for M2, 95.5%, was achieved during the first 55 min, and the max R% for M3 (96.4%) was achieved in the first 35 min, while the max R% for M4, 98.6%, was achieved during the first 35 min.