Assessment of green tea-enabled iron/calcined bentonite nanocomposites for phosphate removal and recovery

We suggest using green tea enabled iron nanoparticles supported on calcined bentonite (G-nZVI/B) to remove and recover phosphate from synthetic wastewater. The nanocomposites are proposed as an eco-innovative adsorbent material for wastewater treatment plants. Adsorption columns packed with this novel nanocomposite would help overcome the footprint obstacle of wastewater treatment plants in a cost-effective way. We assessed the effect of various iron (Fe) /calcined bentonite (Cal-B) mass ratios (2 g Cal-B/2 g Fe, 2 g Fe, 2 g Cal-B/0.56 g Fe) and Fe/Green tea extract (GT) volumetric ratios (1/1, 1/0.5, 1/0.1) in 9 different nanocomposites (GnZVI/B). The nanocomposites were characterized using BET, SEM, TEM, FT-IR, XRD, and XPS. The recipe for the optimized nanocomposite composition was found as follows: NC2 (Fe: 2 g, Calcined bentonite: 2 g, Fe/Green tea extract: (1/0.5) (V/V)). TEM analysis demonstrated that size of the iron nanoparticles (INPs) was within the range of 8-30 nm for NC2. Adsorption isotherms and kinetic models were carried out with the optimized nanocomposite under the following conditions: Room temperature; adsorbent dosage = 5 g/L; initial phosphate concentration: 10-900 mg/L, and contact time = 5-1500 min. The results revealed that the maximum adsorption capacity was 58.60 mg/g using Sips model (R-2 = 0.959), and the adsorption rate constant was 23.017 mg/(g. min) using Elovich model (R-2 = 0.971). Chemisorption was suggested to be the major mechanism of phosphate removal from an aqueous solution. The adsorption and recovery efficiencies were determined to be 98.60% and 53.48% using 1 g of NC2 with 50 mg/L initial phosphate concentration.

Automated summary

In this study, green tea enabled iron nanoparticles supported on calcined bentonite were proposed for the removal and recovery of phosphate from wastewater. The optimized nanocomposite showed high adsorption capacity and rate, making it a promising adsorbent for wastewater treatment.