Optimized removal of hexavalent chromium from water using spent tea leaves treated with ascorbic acid

Abstract

Spent tea leaves were functionalized with ascorbic acid to obtain treated tea waste (t-TW) to encourage the adsorption of hexavalent chromium from water. The adsorption removal of Cr(VI) was systematically investigated as a function of four experimental factors: pH (2–12), initial Cr(VI) concentration (1–100 mg L−1), t-TW dosage (0–4 g L−1), and temperature (10–50 °C) by following a statistical experimental design. A central composite rotatable experimental design based on a response surface methodology was used to establish an empirical model that assessed the individual and combined effects of factors on adsorptive removal of Cr(VI). The model was experimentally verified and statistically validated then used to predict optimal adsorption removal of Cr(VI) from water. At optimized conditions, ≥ 99% of 1 mg L−1 Cr(VI) can be removed by 4 g L−1 t-TW at a pH of 9. The adsorptive mechanism was assessed by conducting kinetics and equilibrium studies. The adsorption of Cr(VI) by t-TW followed a pseudo-second-order kinetics model (k2 = 0.001 g mg−1 h−1) and could be described by Langmuir and Temkin isotherms, indicating monolayer adsorption and predominantly adsorbate-adsorbent interactions. The t-TW exhibited a competitive Cr(VI) adsorption capacity of 232.2 mg g−1 compared with the other low-cost adsorbents. These results support the utilization of tea waste for the removal of hazardous metal contaminants from aqueous systems.

Magnetic NH2-MIL-101(Al)/Chitosan nanocomposite as a novel adsorbent for the removal of azithromycin: modeling and process optimization

“…Compared to Langmuir isotherm model, Freundlich isotherm model had the poorest fit with experimental data, as determined by comparison of R 2 and χ 2 values. However, high values of k F (60.837 L mg -1 ) and n parameter (greater than 1) indicated that adsorption of adsorbate on adsorbent was acceptable/feasible 54 , 55 . Table 3 reveals that the experimental data are less consistent with the Temkin isotherm model than either of the previous two models.…”

Characterization of activated carbon produced from the green algae Spirogyra used as a cost-effective adsorbent for enhanced removal of copper(ii): application in industrial wastewater treatment

“…The broad absorption band around 3600–3200 cm −1 is related to the presence of stretching vibrations of hydrogen bonds (hydroxyl groups –OH from carboxyls, phenols or alcohols), or stretching N–H groups in primary amines, secondary amines, and/or amides. 33,38 The low-intensity peak was around 3340 cm −1 in SP, which shifted to 3440 cm −1 in SPAC. This may be due to the pyrolysis process, which weakened the hydrogen bonding interaction.…”

The Dynamic Behaviour of a Binary Adsorbent in a Fixed Bed Column for the Removal of Pb2+ Ions from Contaminated Water Bodies

“…The mass transfer zone (MTZ) represents the length of unused bed and is calculated using the following equation [17]:…”

“…Agricultural waste materials in particular have been widely researched as potential adsorbents for metal removal from contaminated water sources [14][15][16]. Some of these adsorbents include the use of spent tea leaves [17], fruit peels [18] and banana peel powder [19]. The recycling of waste materials is considered a sustainable approach towards waste management practices serving to solve disposal problems which aligns with the circular economy [20].…”