Enhancement of sorption capacity of cocoa shell biomass modified with non-thermal plasma for removal of both cationic and anionic dyes from aqueous solution

Deep insights into kinetics, optimization and thermodynamic estimates of methylene blue adsorption from aqueous solution onto coffee husk (Coffee arabica) activated carbon

In the current study, an attempt was made to synthesize coffee husk (CH) activated carbon by chemical modification approach (sulphuric acid-activated CH (SACH) activated carbon) and was used as a valuable and economical sorbent for plausible remediation of Methylene blue (MB) dye. Batch mode trials were carried out by carefully varying the batch experimental variables: SACH activated carbon (SACH AC) dosage, pH, initial dye concentration, temperature, and contact time. The optimum equilibrium time for adsorption by SACH activated carbon was obtained as 60 min, and the maximum adsorption took place at 30 °C. Morphological and elemental composition, crystallinity behaviour, functional groups, and thermal stability were examined using SEM with EDX, XRD, FTIR, BET, TGA, and DTA and these tests showed successful production of activated carbon. The outcomes showed that chemical activation enhanced the number of pores and roughness which possibly maximized the adsorptive potential of coffee husk. The Box-Benken design (BBD) was used to optimize the MB dye adsorption studies and 99.48% MB dye removed at SACH AC dosage of 4.83 g/L at 30 °C for 60 min and pH 8.12, and the maximum adsorption was yielded for sulphuric acid-activated coffee husk carbon carbon with 88.1 mg/g maximum MB adsorption capacity. Langmuir- Freundlich model deliberately provided a better fit to the equilibrium data. The SACH AC-MB dye system kinetics showed a high goodness-of-fit with pseudo second order model, compared to other studied models. Change in Gibbs's free energy (ΔGo) of the system indicated spontaneity whereas low entropy value (ΔSo) suggested that the removal of MB dye on the SACH activated carbon was an enthalpy-driven process. The exothermic nature of the sorption cycle was affirmed by the negative enthalpy value (ΔHo). The adsorptive-desorptive studies reveal that SACH AC could be restored with the maximum adsorption efficiency being conserved after the fifth cycles. Overall, the outcomes revealed that sulphuric acid-activated coffee husk activated carbon (SACH AC) can be used as prompt alternative for low-cost sorbent for treating dye-laden synthetic wastewaters.

Effect of Cold Atmospheric Pressure Argon Plasma Jet Treatment on the Freeze-Dried Mucilage of Chia Seeds (Salvia hispanica L.)

In the present study, the effects of the treatment of chia seeds with a cold atmospheric pressure plasma jet (CP) using argon as a working gas for different times (30, 60, and 120 s) on the rheological, structural, and microstructural properties of the freeze-dried mucilages at -54 °C were investigated. All mucilage gels showed pseudoplastic flow behavior, and CP treatment of chia seeds increased the viscosity of mucilages, probably due to the cross-linking between polymer molecules. The dynamic rheological analysis revealed that all mucilages were elastic gels and that CP treatment improved the elastic properties in a treatment time-dependent manner. Large amplitude oscillatory shear (LAOS) results showed that freeze-dried mucilages showed Type I strain-thinning behavior. Similar to small amplitude oscillatory shear (SAOS) results, CP treatment has affected and improved the large deformation behavior of mucilages depending on treatment time. Meanwhile, Fourier transform infrared spectroscopy (FTIR) revealed the incorporation of hydroxyl groups onto the surface and the formation of C-O-C glycosidic bonds during plasma treatment. Scanning electron microscope (SEM) micrographs showed the formation of denser structures with CP treatment time. Regarding color properties, CP treatment decreased the lightness values of mucilages. Overall, this study showed that CP is an effective way to modify both the SAOS and LAOS properties of freeze-dried chia mucilage and improve viscosity.

Plasma Surface Engineering of Natural and Sustainable Polymeric Derivatives and Their Potential Applications

Recently, natural as well as synthetic polymers have been receiving significant attention as candidates to replace non-renewable materials. With the exponential developments in the world each day, the collateral damage to the environment is incessant. Increased demands for reducing pollution and energy consumption are the driving force behind the research related to surface-modified natural fibers (NFs), polymers, and various derivatives of them such as natural-fiber-reinforced polymer composites. Natural fibers have received special attention for industrial applications due to their favorable characteristics, such as low cost, abundance, light weight, and biodegradable nature. Even though NFs offer many potential applications, they still face some challenges in terms of durability, strength, and processing. Many of these have been addressed by various surface modification methodologies and compositing with polymers. Among different surface treatment strategies, low-temperature plasma (LTP) surface treatment has recently received special attention for tailoring surface properties of different materials, including NFs and synthetic polymers, without affecting any of the bulk properties of these materials. Hence, it is very important to get an overview of the latest developments in this field. The present article attempts to give an overview of different materials such as NFs, synthetic polymers, and composites. Special attention was placed on the low-temperature plasma-based surface engineering of these materials for diverse applications, which include but are not limited to environmental remediation, packaging, biomedical devices, and sensor development.

Egg-derived porous plasma modified clay composite for wastewater remediation

Clays are often envisaged as an alternative to activated carbon for wastewater pollutant adsorption. However, conclusive results have only been obtained for clays heavily chemically modified. In this study, a greener approach is proposed to improve the retention capacity of clays. It consists in mixing clay (C) with eggshell (ES) and calcine, and then exposing to gliding arc plasma (ESC-800/PL). The resulting materials were characterized by nitrogen physisorption, FTIR, XRD, TGA/DTG, and point of zero charge analyses. The preparation gives porous platelet agglomerates resulting from the kaolinite-metakaolinite transition, thereby increasing their internal specific surface area and capacity to retain pollutants. This granular distribution is kept stable by partial pozzolanic reactions avoiding deagglomeration. The specific surface area and total pore volume increased respectively from 14 m² g^-1 and 0.049 cm³ g^-1 to 89 m² g^-1 and 0.061 cm³ g^-1 leading to an enhanced removal efficiency of Fast Green and Orange G dyes from polluted water. The maximum adsorption capacity occurred at 298 K attaining values of 32.34 and 14.78 mg g^-1 for OG and FG, respectively. The pH plays a crucial role in the maximum sorption of dyes, and the experimental data were successfully adjusted to pseudo-first-order kinetic and Liu isotherm model.

Cocoa bean shells: a review into the chemical profile, the bioactivity and the biotransformation to enhance their potential applications in foods

During processing, cocoa bean shells (CBS) are de-hulled from the bean and discarded as waste. Undermined by its chemical and bioactive composition, CBS is abundant in dietary fiber and phenolic compounds that may serve the valorization purpose of this by-product material into prebiotic and functional ingredients. In addition, the cell-wall components of CBS can be combined through enzymatic feruloylation to obtain feruloylated oligo- and polysaccharides (FOs), further enhancing the techno-functional properties. FOs have attracted scientific attention due to their prebiotic, antimicrobial, anti-inflammatory and antioxidant functions inherent to their structural features. This review covers the chemical and bioactive compositions of CBS as well as their modifications upon cocoa processing. Physical, chemical, and enzymatic approaches to extract and bio-transform bioactive components from the cell wall matrix of CBS were also discussed. Although nonspecific to CBS, studies were compiled to investigate efforts done to extract and produce feruloylated oligo- and polysaccharides from the cell wall materials.

Plasma-enhanced modification of polysaccharides for wastewater treatment: A review

In this work, novel polysaccharide-based sorbents modified with plasma technologies are discussed. Plasma selectively modifies the surface properties by generating specific moieties, enhancing adsorption performance, and the physical-chemical properties of the material without modifying its bulk properties. Among plasma technologies, cold plasma is more suitable and energy-efficient, since thermal-sensitive materials could be modified using this technology. Besides, atmospheric-pressure plasma systems possess the required features to scale-up plasma technologies for surface modification of sorbents. Moreover, a big challenge is the semi-continuous operation to modify sorbents as it would decrease overall process costs. Due to its low-cost and extensive availability, polysaccharide-based sorbents are promising substrates for plasma-enhanced modification to develop highly efficient adsorbents. The development of polysaccharide-based materials includes modified cellulose, chitosan, or lignocellulosic materials with functionalities that increase adsorption capacity and selectivity towards a specific organic or inorganic pollutant.

Plasma jet assisted carbonization and activation of coffee ground waste

Activated carbon has been extensively utilized to adsorb pollutants generated by industrial activities. There have been many attempts to efficiently produce activated carbon from spent coffee grounds in the field of environmental technology. In this study, the feasibility of the novel production of activated carbon from coffee ground waste using a plasma jet was evaluated. A rotating gliding arc generator was designed that used an N₂ plasma jet for the carbonization process and a CO₂ plasma jet for the activation process. It was confirmed that the coffee ground waste could be carbonized and activated by the two plasma jets in the same reactor. The characteristics of the surface morphologies of the activated carbon samples varied depending on the plasma treatment conditions, such as the electric power of the plasma jet and the treatment time. The results implied that the adsorption capacity of the activated carbon could be optimized by regulating the pore size and distribution based on the plasma treatment conditions with regard to the molecular size of the target adsorbate.

Insight into the removal process mechanism of pharmaceutical compounds and dyes on plasma-modified biomass: the key role of adsorbate specificity

The reason that some molecules, but not others, are easily adsorbed was not fully understood. In order to spotlight the effect of morphological structure and surface functional composition of adsorbate rather than focusing only on the nature of adsorbent as in most of literature reports, this work reports the biosorption of two dyes (anionic Orange G and cationic malachite green) and two pharmaceuticals (Ibuprofen and ampicillin) as target representative contaminants onto plasma-modified cocoa shell (CPHP) used as alternative low-cost adsorbent. As results, when molecules were mixed in solution and then exposed to a substrate, the factors that affect adsorption include the relative solvation of the adsorbates, the ability of each molecule to adhere to the surface, and the degree of interaction between the molecules once they were adsorbed. The maximum adsorbed amounts at 298 K of OG, MG, IBP, and AMP were 23.96, 14.65, 13.99, and 06.66 mg/g, respectively. The most solvated molecules may not adsorb rapidly to the surface, while comparatively, the less soluble molecules will aggregate, so as to maximize self-interactions via Van der Waals, hydrogen bonds or other interactions. This work demonstrated that the adsorbate intrinsic properties could play a significant role in the adsorption process. Hence, properties such as functional active groups, dimensions, and hydrophobicity were the determining parameters in the adsorption process mechanism. Accordingly, the pharmaceuticals biosorption mechanism involved π-π bonding, hydrophobic effect, electrostatic interaction, and van der Waals forces whereas the dye biosorption mechanism was dominated as well known by electrostatic attraction and hydrogen bonding phenomenon. Experimental parameters such as initial pH of solution and contact time were optimized. The optimum pH values were 2.0 for ibuprofen (IBP) and 7.0 for ampicillin (AMP). The kinetics of adsorption and the experimental isotherms data were analyzed using non-linear models. Results indicated that Avrami fractional order was the most successfully fitted model for pharmaceutical biosorption and based on the statistical values of SD and R²_adj parameters, Liu isotherm was the most successfully fitted model.

Cocoa Bean Shell-A By-Product with Nutritional Properties and Biofunctional Potential

Cocoa bean shells (CBS) are one of the main by-products from the transformation of cocoa beans, representing 10%‒17% of the total cocoa bean weight. Hence, their disposal could lead to environmental and economic issues. As CBS could be a source of nutrients and interesting compounds, such as fiber (around 50% w/w), cocoa volatile compounds, proteins, minerals, vitamins, and a large spectrum of polyphenols, CBS may be a valuable ingredient/additive for innovative and functional foods. In fact, the valorization of food by-products within the frame of a circular economy is becoming crucial due to economic and environmental reasons. The aim of this review is to look over the chemical and nutritional composition of CBS and to revise the several uses that have been proposed in order to valorize this by-product for food, livestock feed, or industrial usages, but also for different medical applications. A special focus will be directed to studies that have reported the biofunctional potential of CBS for human health, such as antibacterial, antiviral, anticarcinogenic, antidiabetic, or neuroprotective activities, benefits for the cardiovascular system, or an anti-inflammatory capacity.

Removal and enrichment of Cr(VI) from aqueous solutions by lotus seed pods

Chromium (Cr(VI)) is highly toxic and carcinogenic. Cr(VI) water pollution has become more and more serious. This article reports on a study in which lotus seed pods (LSP), an agricultural waste product, was used to efficiently remove Cr(VI) from an aqueous solution, and the carbonization product of LSP after the removal of Cr(VI) (CPLSP) can be regarded as a resource containing Cr. Cr(VI) removed by LSP fits a pseudo-second-order model. pH levels greatly influence the amount of Cr removed. The maximum removal of Cr(VI) by LSP in aqueous solution was 153.85 mg/g. The possible removal mechanism is absorption, redox, and reabsorption based upon SEM/EDS, FT-IR, and XPS spectra results. The Cr content of CPLSP was 42.95% by ammonium persulfate oxidation titrimetric method. These results suggest that LSP can be an excellent, low cost, biomaterial for removing and enriching Cr(VI) from an aqueous solution. PRACTITIONER POINTS: Lotus seed pods are an efficient adsorbent for Cr(VI) from aqueous solutions. The Cr removal by lotus seed pods occurs via absorption, redox, and reabsorption. Cr can be captured after the pods are carbonized. Lotus seed pods can be applied to the removal and enrichment of Cr(VI) from waste water.

Recent advances for dyes removal using novel adsorbents: A review

Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Numerous researchers have attempted to seek or design alternative materials for dye adsorption. However, using various novel adsorbents to remove dyes has not been extensively reviewed before. In this review, the key advancement on the preparation and modification of novel adsorbents and their adsorption capacities for dyes removal under various conditions have been highlighted and discussed. Specific adsorption mechanisms and functionalization methods, particularly for increasing adsorption capacities are discussed for each adsorbent. This review article mainly includes (1) the categorization, side effects and removal technologies of dyes; (2) the characteristics, advantages and limitations of each sort of adsorbents; (3) the functionalization and modification methods and controlling mechanisms; and (4) discussion on the problems and future perspectives about adsorption technology from adsorbents aspects and practical application aspects.

Date palm ash-MgAl-layered double hydroxide composite: sustainable adsorbent for effective removal of methyl orange and eriochrome black-T from aqueous phase

Date palm ash (DPA) and MgAl-layered double hydroxide (LDH) composites were synthesized by the co-precipitation method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET). The DPA-MgAl-LDH (DPA/MgAl) composites were employed for the removal of methyl orange (MO) and eriochrome black-T (EBT) from aqueous phase. Incorporation of 33.33% (w/w) DPA into the layers of MgAl increased the surface area from 44.46 to 140.65 m²/g, which leads to the improved adsorption performance. The maximum adsorption capacity of DPA/MgAl (1:2) at 298 K was 242.98 and 425.16 (mg/g) for MO and EBT, respectively. The adsorption data of dyes were adequately fitted by a pseudo-second-order and Langmuir isotherm model. The composite showed excellent reusability performance up to three cycles. Addition of DPA into MgAl-LDH resulted in an effective low-cost adsorbent for decontamination of dyes from wastewater. Graphical abstract ᅟ.

Gliding arc plasma pre-treatment of kaolin in spatial post-discharge mode for removal of Reactive Red 2 dye from aqueous solution

This study investigates the ability of spatial post-discharge mode functionalized kaolin to remove textile dye Reactive Red 2 from aqueous solution compared to that of the raw kaolinite. To fulfill the aim, the removal conditions, including plasma exposure time, processed mode (direct and post-discharge), pH of the aqueous dye solution, initial dye concentration and adsorbent dosage, were investigated. The changes that occur on clay surfaces before and after gliding arc plasma treatment were followed by Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen physisorption. The point of zero charge and the changes of the textural properties after gliding arc plasma treatment were also examined. The experimental data were analyzed using pseudo-first-order, pseudo-second-order and empirical Elovich models. The diffusion phenomenon was also studied. The results obtained indicate that spatial post-discharge pre-treatment of kaolin deeply influences the functional groups of some of its minerals as well as the morphology and texture of its particles. Consequently, at room temperature (∼30 °C), the maximum adsorption capacities of natural raw kaolin clay were tripled after treatment with gliding arc plasma in spatial post-discharge mode and were almost doubled after the direct treatment mode.