Black Tea Waste as Green Adsorbent for Nitrate Removal from Aqueous Solutions

• Published in: Materials Vol. 16; no. 12; p. 4285
• Main Authors: Bondarev, Andreea, Popovici, Daniela Roxana, Călin, Cătalina, Mihai, Sonia, Sȋrbu, Elena-Emilia, Doukeh, Rami
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09-06-2023; MDPI
• Subjects: Activated carbon; Adsorbents; Adsorption; Aqueous solutions; Arsenic; Black tea; Chemical elements; Climatic changes; Colorectal cancer; Drinking water; Food contamination & poisoning; Infectious diseases; Infrared analysis; Isotherms; Low cost; Methylene blue; Multilayers; Nitrate removal; Nitrates; Pollutants; Reagents; Recycling; Sorbents; Tea; Thermal analysis; Thermogravimetric analysis; Thyroid diseases; X ray analysis; Germany; tea waste; adsorption; nitrate; pollution
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16124285

The aim of the study was to prepare effective low-cost green adsorbents based on spent black tea leaves for the removal of nitrate ions from aqueous solutions. These adsorbents were obtained either by thermally treating spent tea to produce biochar (UBT-TT), or by employing the untreated tea waste (UBT) to obtain convenient bio-sorbents. The adsorbents were characterized before and after adsorption by Scanning Electron Microscopy (SEM), Energy Dispersed X-ray analysis (EDX), Infrared Spectroscopy (FTIR), and Thermal Gravimetric Analysis (TGA). The experimental conditions, such as pH, temperature, and nitrate ions concentration were studied to evaluate the interaction of nitrates with adsorbents and the potential of the adsorbents for the nitrate removal from synthetic solutions. The Langmuir, Freundlich and Temkin isotherms were applied to derive the adsorption parameters based on the obtained data. The maximum adsorption intakes for UBT and UBT-TT were 59.44 mg/g and 61.425 mg/g, respectively. The data obtained from this study were best fitted to the Freundlich adsorption isotherm applied to equilibrium (the values R
= 0.9431 for UBT and R
= 0.9414 for UBT-TT), this assuming the multi-layer adsorption onto a surface with a finite number of sites. The Freundlich isotherm model could explain the adsorption mechanism. These results indicated that UBT and UBT-TT could serve as novel biowaste and low-cost materials for the removal of nitrate ions from aqueous solutions.