Application of carbon from pomegranate husk for the removal of ibuprofen, cadmium and methylene blue from water

The presence of pharmaceutical products, dyes, and toxic metal ions in water is a major problem worldwide. This work developed low-cost pomegranate-based materials to uptake ibuprofen, cadmium and methylene blue from water. Pomegranate husks (PPH) were carbonized at 400 °C to form carbonized pomegranate husk (CPH), and nanoparticles were loaded into the carbon surface (NPH) by co-precipitation. SEM micrographs showed that the morphology of carbon was highly porous compared to pristine pomegranate husk. The data for BET revealed that CPH and NPH, had about a 20-fold increase in surface area of 142 m2/g and 190 m2/g respectively compared with 9.27 m2/g for PPH. The composites exhibited larger pore sizes and volumes. TEM images confirmed the loading of nanoparticles. The FTIR results showed that the materials had on their surface oxygenated groups such as -OH, -C]O, -COC and other groups like -NH and -C]C which are anticipated to play an essential role in the sorption of the pollutants. It was found that removal efficiency increased when there was a progressive increase in pollutant concentration for all adsorbents. The best pH value of the solution for the sorption processes was pH 8. The recorded adsorption capacities at pH 8 for Cd(II), IBU and MB were 92.85, 39.77 and 95.89 mg/g for NPH, 72.60, 32.58 and 80.59 mg/g for CPH and 32.78, 16.12 and 40.79 mg/g for PPH. Contact time studies showed three sorption steps. Step 1: rapid increase at the initial stage. Step 2: marginal uptake. Step 3: plateau. The trends indicated that sorption was influenced by temperature variation. The data for the thermodynamic parameter △Ho suggest that all the sorption processes were endothermic; the obtained positive values indicate this. The △Ho for PPH was between (64.33-69.08 kJ/mol), 82.84-86.03 kJ/mol for CPH and 87.17-88.96 kJ/mol for NPH. For PPH, molecular interactions were physisorption, and chemisorption for CPH and NPH. The △So has positive values, showing increased freedom during the sorption. The adsorbents followed PSO based on uptake processes involving syngenetic mechanisms.

Pine bark crosslinked to cyclodextrin for the adsorption of 2-nitrophenol from an aqueous solution

Adsorbents that are less expensive and more effective at removing organic micropollutants from wastewater have been developed through several approaches. Pine bark was treated with sodium hydroxide and then cross-linked to cyclodextrin using hexamethylene diisocyanate, in this study as an efficient adsorbent in the removal of 2-nitrophenol. FTIR, TGA and pHpzc analysis were used to characterize the biosorbent. The effects of pH, adsorbent mass, contact time and initial concentration on 2-nitrophenol removal was examined through batch adsorption studies. Pine bark crosslinked to cyclodextrin (PB-CD) surface functionalities was confirmed by FTIR analysis. It was discovered that solution pH, adsorbent mass, concentration and contact time all played a crucial role in the 2-nitrophenol uptake on PB-CD biosorbent and pine bark (PB) treated with sodium hydroxide. 2-Nitrophenol equilibrium was achieved with 0.05 g of adsorbents, with an initial concentration of 100–200 mg/dm3 at pH 5 after 60 min. The pseudo-second-order kinetic model and the Langmuir isotherm model significantly fitted the adsorption process. The Langmuir maximum capacities for PB and PB-CD were 47.36 mg/g and 77.82 mg/g, respectively. Overall, in the removal of 2-nitrophenol from an aqueous solution, PB-CD biosorbent is more cost-effective and efficient, in comparison with previously reported biosorbents in literature.

The Improvement of Natural Thai Bentonite Modified with Cationic Surfactants on Hexavalent Chromium Adsorption from an Aqueous Solution

This work was performed to evaluate the adsorption properties of modified Thai bentonites (MTBs) on hexavalent chromium (Cr(VI)) by using a popularly capable surfactant (hexadecyltrimethylammonium bromide (HDTMA)) compared to an alternative surfactant (cetylpyridinium chloride (CPC)). The adsorption properties of the surfactant load, adsorbent weight, contact time, initial Cr(VI) concentration, and temperature of the MTBs were evaluated. The results revealed that a higher surfactant load significantly affected the Cr(VI) adsorption, and the equilibrium adsorption was achieved at 60 min. The adsorption capacity improved when the adsorbent weight, contact time, initial concentration, and temperature increased as the highest adsorption capacities of 1CPC and 1HDTMA were 45.55 and 46.03 mg g-1, respectively. The isotherm and kinetic adsorptions were described by the Freundlich model and pseudo-second-order model, respectively, while thermodynamics indicated endothermic adsorption. After adsorption, X-ray absorption near-edge structure and extended X-ray absorption fine structure data showed that Cr ions did not change the valency state between Cr(VI) and Cr(III). Additionally, the adsorption mechanism can be depicted as the ion exchange between the Cr(VI) ion and the surfactant molecule. Structural evaluations by XRD, FTIR, FESEM, EDS, and TEM found that both MTBs (1CPC and 1HDTMA) with the best adsorption performance for Cr(VI) had obvious changes at both the interlayer structure and the external surface. The interlayer spacing was expanded from 14.85 Å to 20.48 Å (1CPC) and 18.79 Å (1HDTMA), and the new functional groups (CH2 scissoring, C–H symmetric stretching, C–H asymmetric stretching, and N–CH3 scissoring) and elemental compositions (Br and Cl) were observed in both MTBs. They demonstrated that the complete intercalation of surfactant molecules on bentonite structures supported Cr(VI) adsorption. Overall, the data indicate that MTBs were perfectly adsorbed on Cr(VI), and CPC was demonstrated to be a cheap alternative agent due to its adsorption capacity compared to the popularly capable HDTMA.