Eriochrome black adsorption on yellow passion fruit peel (Passiflora edulis f. Flavicarpa) treated with sodium hydroxide and nitric acid: study of adsorption isotherms, kinetic models and thermodynamic parameters

High removal of volatile organic compounds on hierarchical carbons prepared from agro-industrial waste of banana fruit production for air decontamination

Activated carbons were prepared from residues from agro-industrial banana production (banana pseudostem) and evaluated in the capture of five different volatile organic compounds (VOCs): dichloromethane, chloroform, ethyl acetate, hexane, and cyclohexane. The biomass was first submitted to a hydrothermal treatment in the presence of KOH or ZnCl2 as activating agents, followed by a dry pyrolysis. This new advance in methodology contributes to producing activated carbons with hierarchical porosity and high surface areas (701-1312 m2 g-1), promoting increased interest in managing waste from banana fruit agricultural production. VOC capture studies were performed by thermal analysis, and capture capacities were similar to or higher than those presented in the literature. Higher adsorption capacities were related to the amount of available micropores, and the capture capacity was enhanced by the contribution of small mesopores. As the highest adsorbed amounts of dichloromethane (933 mg g-1 at 25 °C) were obtained for the material activated with ZnCl2 (1:3), further studies were carried out for this system. The experimental data was fitted using a pseudo-first-order kinetic model. A study was carried out in different atmospheres (He, N2, air), showing that co-adsorption is occurring. Under simulated environmental conditions, the capture capacity decreased slightly at equilibrium, and the new adsorbent was used for up to ten cycles without significantly losing its efficiency, indicating good application in the field.

Powdered silk: A promising biopolymer for the treatment of dye contaminated water

Discharge of textile dye effluents into water bodies is creating stress to aquatic life and contaminating water resources. In this study, a new biopolymer adsorbent silk fibroin (SF) was prepared from Bombyx mori silk fibroin (SF) and used for removal of Solochrome Black-T (SB-T) from water. This innovative adsorbent exhibits an exceptional adsorption capacity of 20.08 mg/g, achieving a removal efficiency of approximately 98.6 % within 60 min. Notably, the powdered SF adsorbent demonstrates rapid kinetics, surpassing the performance of previously reported similar adsorbents in adsorption capacity and reaction speed. The molecular weight and particle diameter of the material were observed to be > 1.243 kDa and 3 μm, respectively. The experimental investigations were performed on different parameters, viz., adsorbent dosage, contact time, repeatability, and desorption-adsorption study. The experimental data well fit for the Langmuir model (R2 = 0.937, qmax = 20.08 mg/g) and the pseudo-second-order kinetics (R2 = 0.921 and qe = 1.496 mg/g). Compared to the adsorbents reported in the literature, the newly prepared SF showed high adsorption capacity and faster kinetics to address real-life situations. The novelty of this work extends beyond its remarkable adsorption capabilities. The SF adsorbent offers a cost-effective, sustainable solution and regenerable adsorption material with minimal negative environmental impacts. This regenerability, with its versatility and broad applicability, positions powdered SF fibroin as a transformative technology in water treatment and environmental protection.

Removal of Cr(VI) from water by in natura and magnetic nanomodified hydroponic lettuce roots

Biosorption is a viable and environmentally friendly process to remove pollutants and species of commercial interest. Biological materials are employed as adsorbents for the retention, removal, or recovery of potentially toxic metals from aqueous matrices. Hexavalent chromium is a potential contaminant commonly used in galvanoplasty and exhibits concerning effects on humans and the environment. The present work used in natura lettuce root (LR) and nanomodified lettuce root (LR-NP) for Cr(VI) adsorption from water medium. The nanomodification was performed by coprecipitation of magnetite nanoparticles on LR. All materials were morphologically and chemically characterized. The conditions used in removing Cr(VI) were determined by evaluating the pH at the point of zero charge (pHPZC = 5.96 and 6.50 for LR and LR-NP, respectively), pH, kinetics, and sorption capacity in batch procedures. The maximum sorption capacity of these materials was reached at pH 1.0 and 30 min of adsorbent-adsorbate contact time. The pseudo-second-order kinetic equation provided the best adjustments with r2 0.9982 and 0.9812 for LR and LR-NP, respectively. Experimental sorption capacity (Qexp) results were 4.51 ± 0.04 mg/g, 2.48 ± 0.57 mg/g, and 3.84 ± 0.08 mg/g for LR, NP, and LR-NP, respectively, at a 10 g/L adsorbent dose. Six isothermal models (Langmuir, Freundlich, Sips, Temkin, DR, and Hill) fit the experimental data to describe the adsorption process. Freundlich best fit the experimental data suggesting physisorption. Despite showing slightly lower Qexp than LR, LR-NP provides a feasible manner to remove the Cr(VI)-containing biosorbent from the medium after sorption given its magnetic characteristic.

Remediation of Cd (II) Ion from an Aqueous Solution by a Starch-Based Activated Carbon: Experimental and Density Functional Theory (DFT) Approach

Heavy metal ion pollution is a serious threat for aquatic and terrestrial living beings. Adsorption is a facile process to encounter heavy metal pollution. Various types of adsorbents have been developed and used for environmental remediation. Activated carbon is one of the cheapest adsorbents derived from various biomass. In this work, the adsorption of cadmium ions (Cd (II)) with starch-based activated carbon (AC) having a specific surface area of 1600 m2 g−1 was investigated in a series of batch laboratory studies. The effective operating parameters, such as initial pH (pH0), initial concentration of metal ions, contact time, and temperature on the adsorption, were investigated. Validation of the kinetic study shows that the adsorption process is better predicted by the pseudo-second-order model. The extended Freundlich and Langmuir isotherms were applied to the study. The results show that the metal ion adsorption capacities of activated carbon increased with increasing pH, and it was found that maximum adsorption (284 mg g−1) of Cd (II) was achieved at pH solution of 5.5–6. The thermodynamic parameters, such as ∆G, ∆H, and ∆S, were found to be −17.42 kJ mol−1, 8.49 kJ mol−1, and 58.66 J mol−1 K−1, respectively, revealing that the adsorption mechanism is endothermic, spontaneous, and feasible. Furthermore, the density functional theory simulations demonstrated that the activated carbon strongly interacted with toxicity and mobility, so it is very urgent to remove this species from industrial wastewater before it is discharged into the environment. The adsorption energy calculated for all interactive sites was negative (−43.41 kJ mol−1 to −967.74 kJ mol−1), showing effective interaction between the adsorbate and adsorbent. The PDOS clearly shows that there is a stronger overlapping at the Femi level between the d orbital of the Cd ion and the p orbital of the O atom, showing a strong interaction and confirming the chemical bond formation between the Cd (II) ion and O atom.

Utilization of fruit and vegetable waste to produce value-added products: Conventional utilization and emerging opportunities-A review

Fruit and vegetables are one of the most consumed commodities globally, accounting for more than 42% of total food wastage. These vegetal foods can be consumed raw, processed, or taken as an addition to other food items. The continuous rise in population, in addition to technological advancements, has led to an imbalance in demand supply, resulting in increased food wastage globally. Although source reduction and recycling have shown promising results, more evaluations concerning economics and environmental impacts need to be given importance. The need of the hour lies in finding a possible method towards effective utilization for fruit and vegetable waste to generate value-added products which are more eco-friendly, cheaper, and sustainable. Thus, this article attempts to focus on the conventional and emerging opportunities of fruit and vegetable waste to generate value-added products. Conventional utilization, namely briquetting, waste to energy conversion, enzymatic degradation, and adsorption, as well as emerging opportunities in the areas of nutraceuticals, packaging, flavoring agents, and waste induced nanoparticles, have been emphasized. Additionally, recommendations and future perspectives towards better utilization of vegetal waste have been given importance. This review aims to narrow down the path towards evaluating the most techno-economic and efficient waste management technique for fruits and vegetable valorization, which can be promoted in the long term.

Removal of azo dye from aqueous solution by a low-cost activated carbon prepared from coal: adsorption kinetics, isotherms study, and DFT simulation

The high-risk organic pollutants produced by industries are of growing concern. The highly porous coal-based activated carbon (AC) having a specific surface area of 3452.8 m²/g is used for the adsorption of azo dye from synthetic solution. The sorbent is characterized through BET, SEM, TEM, XRD, FT-IR, TGA, and zeta potential. The sorbent exhibits - 18.7 mV surface charge, which is high enough for making suspension. The maximum dye uptake of 333 mg/g is observed in sorbent under acidic medium. The thermodynamics parameters like ∆G, ∆H, and ΔS were found to be - 12.40 kJ mol^-1, 39.66 kJ mol^-1, and 174.55 J mol^-1 K^-1 at 293 K, respectively, revealing that the adsorption mechanism is spontaneous, endothermic, and feasible. The experimental data follows the Langmuir and D-R models. The adsorption follows pseudo 2nd-order kinetics. DFT investigation shows that the dye sorption onto AC in configuration No. 4 (CFG-4) is more effective, as this configuration has high ∆H (enthalpy change) and adsorption energy (E_ads). This is confirmed by Mullikan atomic charge transfer phenomenon.