Activated Carbon–Modified Iron Oxide Nanoparticles for Cr(VI) Removal: Optimization, Kinetics, Isotherms, Thermodynamics, Regeneration, and Mechanism Study

• Published in: Water, air, and soil pollution air, and soil pollution, 2023-09, Vol.234 (9), p.561-561, Article 561
• Main Authors: Sahu, Uttam Kumar, Tripathy, Swagatika, Gouda, Narayan, Mohanty, Hari Sankar, Sahu, Manoj Kumar, Panda, Sai Prabha, Krishna, Y Murali, Samantaray, Suchismita, Kumar, V Sneha Ravi, Banu, Nikahat, Acharya, Sonali, Jawad, Ali H
• Format: Article
• Language: English
• Subjects: Activated carbon; Adsorbents; Adsorption; air; Ammonium; ammonium carbonate; Ammonium compounds; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Azadirachta indica; Carbon; Carbonates; Chromium; Climate Change/Climate Change Impacts; crystal structure; Earth and Environmental Science; Endothermic reactions; endothermy; Environment; Environmental monitoring; experimental design; Ferric oxide; Hydrogeology; Iron oxides; Isotherms; Kinetics; Leaves; Magnetic saturation; Nanocomposites; Nanoparticles; Neem; Optimization; particle size; Removal; Saturation; soil; Soil Science & Conservation; sorption isotherms; Statistical analysis; surface area; Surface chemistry; thermodynamics; Uptake; Variance analysis; Wastewater; Wastewater treatment; water; Water Quality/Water Pollution
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-023-06588-y

In this study, the waste neem leaves ( Azadirachta indica ) gained visible attraction for neem leaf–activated carbon (NLAC) preparation in the thermal process by using ammonium carbonate as an activating agent. Using NLAC, a nanocomposite of NLAC/Fe 2 O 3 was synthesized by hydrothermal techniques for Cr(VI) elimination from the aqueous solution. The formation of NLAC/Fe 2 O 3 composite was additionally confirmed by the use of various powerful investigative techniques such as FE-SEM, VSM, TEM, EDX, FT-IR, XRD, and BET. The NLAC/Fe 2 O 3 has a saturation magnetization of 1.18 emu/g and surface area and pore volume of 245.2 m 2 /g and 0.038 cm 3 /g, respectively. The composite has crystalline structure and the average particle size of Fe 2 O 3 present on the activated carbon surface was about 14–17 nm. The BBD (Box-Behnken design) model was used for Cr(VI) removal and the obtained R 2 and adj- R 2 values for the model were very high about 0.9805 and 0.9555. The ANOVA data indicated that the Cr(VI) model was a statistically significant one with the F and p values of 39.17 and 0.0001. About 91.4% of Cr(VI) was removed by NLAC/Fe 2 O 3 composite in the optimized condition of 0.05 g of adsorbent dose, solution pH 3.58, and initial Cr(VI) solution of 10.42 mg/L respectively. The adsorption of Cr(VI) on NLAC/Fe 2 O 3 composite was imitated by the Langmuir isotherm model ( R 2 = 0.98), proceeded with the pseudo-second-order kinetics model ( R 2 = 0.99), and the maximum uptake capacity as calculated from the isotherm was 188.71 mg/g. The adsorption process was endothermic and adsorbent can be used for up to four cycles. This study showed that NLAC/Fe 2 O 3 composite could be employed as an effective, affordable cost adsorbent to remove pollutants from wastewater.