Application of cupuassu shell as biosorbent for the removal of textile dyes from aqueous solution

Sorption of ciprofloxacin and enrofloxacin on alkaline cropland soil in semiarid regions: Roles of pH, ionic strength, and ion type

Animals manure and chemical fertilizers are widely applied to agricultural soils to mitigate soil fertility decline resulting from intensive farming practices. However, the use of antibiotics such as ciprofloxacin (CIP) and enrofloxacin (ENR) in these manures introduces certain environmental risks. The sorption of CIP and ENR in soil is influenced by various factors. Soil cations (i.e., Na+, K+, Mg2+, and Ca2+) and artificially introduced ions (NH4+) can affect the sorption behavior of CIP and ENR in alkaline agricultural soils through mechanisms such as ion exchange and competitive sorption. To investigate the effects of ionic strength and ion type on the sorption of antibiotics in alkaline agricultural soil, batch equilibrium experiments were conducted in this study. The results showed that the affinity of alkaline farmland soil to CIP and ENR was poor, and Kd was only 159 L/kg and 89 L/kg, respectively. Increases in temperature and pH inhibited CIP and ENR sorption on soil. Mineral elements in the soil strongly inhibited CIP and ENR sorption. Conversely, NH4+ promoted the Kd values of CIP and ENR by 46% and 221%, respectively. Additionally, under different influencing factors, both the sorption affinity (Kd) and sorption amount of ENR were lower than those of CIP. These findings indicate that ENR has a greater migration potential and poses a greater environmental risk in agricultural soils. Alkaline soil and mineral elements increase the migration potential of CIP, ENR, but the introduction of NH4+ in agricultural production can weaken the migration potential of them.

Removal of Azo Dyes from Water Using Natural Luffa cylindrica as a Non-Conventional Adsorbent

Reducing high concentrations of pollutants such as heavy metals, pesticides, drugs, and dyes from water is an emerging necessity. We evaluated the use of Luffa cylindrica (Lc) as a natural non-conventional adsorbent to remove azo dye mixture (ADM) from water. The capacity of Lc at three different doses (2.5, 5.0, and 10.0 g/L) was evaluated using three concentrations of azo dyes (0.125, 0.250, and 0.500 g/L). The removal percent (R%), maximum adsorption capacity (Qm), isotherm and kinetics adsorption models, and pH influence were evaluated, and Fourier-transform infrared spectroscopy and scanning electron microscopy were performed. The maximum R% was 70.8% for 10.0 g L-1Lc and 0.125 g L-1 ADM. The Qm of Lc was 161.29 mg g-1. Adsorption by Lc obeys a Langmuir isotherm and occurs through the pseudo-second-order kinetic model. Statistical analysis showed that the adsorbent dose, the azo dye concentration, and contact time significantly influenced R% and the adsorption capacity. These findings indicate that Lc could be used as a natural non-conventional adsorbent to reduce ADM in water, and it has a potential application in the pretreatment of wastewaters.

Utilization of aquatic biomass as biosorbent for sustainable production of high surface area, nano- microporous, for removing two dyes from wastewater

The majority of environmental researchers are becoming increasingly concerned with the manufacture of inexpensive adsorbents for the detoxification of industrial effluents. To address one of the significant and well-known pollution issues with certain drains that act as hotspots and contribute to coastal pollution in Alexandria, this study aims to develop an economical, ecologically friendly sorbent. This study assessed the efficacy of a biomass-coated magnetic composite and a magnetic active adsorbent for the removal of two dyes from an industrially contaminated sewer using a wetland plant (Phragmites australis). Using magnetic biosorbent, the biosorption of Xylenol orange and Congo red ions from polluted drain discharge in Abu Qir Bay was evaluated in the current study. Using scanning electron microscopy imaging and Fourier transform infra-red analysis; the surface function and morphology of the nano-biosorbent were examined. At room temperature, the effects of initial dye concentration, pH, contact time, and nano-biosorbent concentration have all been investigated. The greatest percentages that nano-biosorbent can remove from Congo red and Xylenol orange are 97% and 47%, respectively. The removal of the initial Congo red concentration varied from 42 to 97%, while the removal of the initial Xylenol orange concentration varied from 30 to 47%. The adsorption capacity was shown to be strongly pH-dependent; capacity dose as pH value increased, with pH 10 being the ideal pH for Congo red and pH 6 being the ideal pH value for Xylenol orange. The adsorption capacity for Congo red varied between 0.96 and 3.36 and the adsorption capacity for Xylenol orange varied between 0.18 and 17.58. The removal capacity decreased from 3.36 to 0.96 mg/g when the biosorbent dosage was increased from 0.05 to 0.5 g/L for Congo red, in case of Xylenol orange, the removal capacity increased from 0.18 to 17.58 mg/g when the biosorbent dosage was increased from 0.05 to 0.5 g/L. The removal capacity of Congo red increases quickly with time and varied from 1.66 to 1.88 of contact time; while the removal capacity of Xylenol orange varied between 3.08 and 4.62 of contact time. For the dyes under study, kinetics and adsorption equilibrium were examined. Within 180 min, the equilibrium was attained because to the quick adsorption process. For Congo red and Xylenol orange, the highest adsorption capacities were 3.36 and 17.58 mg g-1, respectively. The equilibrium data were assessed using a number of isotherm models, including Langmuir, Freundlich, BET, and Tempkin, while the kinetic data were examined using a variety of kinetic models, including pseudo-first- and pseudo-second-order equations. The pseudo-second-order equation provides the greatest accuracy for the kinetic data and Langmuir model is the closest fit for the equilibrium data.

Biosorption of acid brown 14 dye to mandarin-CO-TETA derived from mandarin peels

Several agronomic waste-materials are presently being widely used as bio-adsorbents for the treatment of toxic wastes such as dyes and heavy metals from industrial activities, which has resulted in critical global environmental issues. Therefore, there is a need to continue searching for more effective means of mitigating these industrial effluents. Synthetic aromatic dyes such as Acid Brown (AB14) dye are one such industrial effluent that is causing a serious global issue owing to the huge amount of these unsafe effluents released into the ecosystem daily as contaminants. Consequently, their confiscation from the environment is critical. Hence, in this study, Mandarin-CO-TETA (MCT) derived from mandarin peels was utilized for the removal of AB14 dyes. The synthesized biosorbent was subsequently characterized employing FTIR, TGA, BET, and SEM coupled with an EDX. The biosorption of this dye was observed to be pH-dependent, with the optimum removal of this dye being noticed at pH 1.5 and was ascribed to the electrostatic interaction between the positively charged sites on the biosorbent and the anionic AB14 dye. The biosorption process of AB14 dye was ideally described by employing the pseudo-second-order (PSO) and the Langmuir (LNR) models. The ideal biosorption capacity was calculated to be 416.67 mg/g and the biosorption process was indicative of monolayer sorption of AB14 dye to MCT biosorbent. Thus, the studied biosorbent can be employed as a low-cost activated biomass-based biosorbent for the treatment of AB14 dyes from industrial activities before they are further released into the environment, thus mitigating environmental contamination.

Effects of acute and chronic chromium stress on the expression of heat shock protein genes and activities of antioxidant enzymes in larvae of Orthetrum albistylum

The dragonfly species Orthetrum albistylum, can accumulate heavy metals from its aquatic environment and thus serves as a biological indicator for monitoring and evaluating water quality. Heat shock proteins (HSPs) play important biological roles in resistance to various types of environmental stress. The full-length cDNA sequences of the heat shock cognate (hsc) 70 and heat shock protein (hsp) 70 genes were cloned from O. albistylum larvae. Relative levels of expression of hsc70 and hsp70 in the head, epidermis, midgut, and adipose tissue were measured by qRT-PCR after chronic and acute contamination of 5-8 instar larvae with chromium (Cr) solution, and under control conditions. Activities of superoxide dismutase (SOD) and catalase (CAT) in chronically contaminated larvae were also measured. Phylogenetic analysis revealed that the cloned hsc70 and hsp70 genes were highly homologous to known HSP70 family members reported in other insects. The mRNA levels of hsc70 and hsp70 did not differ significantly in various larval tissues. Under chronic chromium stress, hsc70 and hsp70 expression were upregulated to a maximum and then downregulated; hsp70 mRNA levels were higher than those of hsc70 at all concentrations of chromium. Under acute chromium stress, hsc70 expression was inhibited at low chromium concentrations and upregulated at chromium concentrations higher than 125 mg/L. However, hsp70 expression was higher than that in the control group and markedly higher than that of hsc70. Changes in SOD and CAT activities displayed consistent trends for different chronic chromium concentrations, first increasing and then decreasing over time. Collectively, these findings demonstrated the response of the HSP family of genes and antioxidant enzymes following exposure to heavy metal stress, as well as their potential applicability as biomarkers for monitoring environmental pollutants.

Banana Peel Powder Biosorbent for Removal of Hazardous Organic Pollutants from Wastewater

Disposing of pollutants in water sources poses risks to human health and the environment, but biosorption has emerged as an eco-friendly, cost-effective, and green alternative for wastewater treatment. This work shows the ability of banana peel powder (BPP) biosorbents for efficient sorption of methylene blue (MB), atrazine, and glyphosate pollutants. The biosorbent highlights several surface chemical functional groups and morphologies containing agglomerated microsized particles and microporous structures. BPP showed a 66% elimination of MB in 60 min, with an adsorption capacity (qe) of ~33 mg g-1, and a combination of film diffusion and chemisorption governed the sorption process. The biosorbent removed 91% and 97% of atrazine and glyphosate pesticides after 120 min, with qe of 3.26 and 3.02 mg g-1, respectively. The glyphosate and atrazine uptake best followed the Elovich and the pseudo-first-order kinetic, respectively, revealing different sorption mechanisms. Our results suggest that BPP is a low-cost biomaterial for green and environmentally friendly wastewater treatment.

Coagulation-adsorption-oxidation for removing dyes from tannery wastewater

Dye removal from tannery wastewater is now a great concern given the ramifications for the environment in which the effluent ends up. Recently, the application of tannery solid waste as a byproduct to remove pollutants from tannery wastewater has garnered increasing attention. This study aims to extract biochar from tannery liming sludge for the removal of dye from wastewater. The activated (600 ºC) biochar was characterized by SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), and surface area analysis utilizing the BET (Brunauer-Emmett-Teller) method and pH_pzc (point of zero charges) analysis. The surface area and pH_pzc of the biochar were determined as 9.29 m²/g and 8.7, respectively. The batch-wise coagulation-adsorption-oxidation was investigated for its efficacy in dye removal. The optimized conditions were as follows: the efficiency of dye, BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) were attained at 94.9%, 95.7% and 93.5%, respectively. SEM, EDS, and FTIR analyses before and after adsorption revealed that the derived biochar could adsorb dye from tannery wastewater. The adsorption behavior of the biochar fitted well to the Freundlich isotherm (R² = 0.9987) and Pseudo 2^nd order (R² = 0.9996) kinetic model. This investigation provides a new dimension for state-of-the-art utilization of tannery solid waste as a feasible strategy to remove dye from tannery wastewater.

Application of Alkali Lignin and Spruce Sawdust for the Effective Removal of Reactive Dyes from Model Wastewater

Today, the emphasis is on environmentally friendly materials. Alkali lignin and spruce sawdust are suitable natural alternatives for removing dyes from wastewater. The main reason for using alkaline lignin as a sorbent is the recovery of waste black liquor from the paper industry. This work deals with removing dyes from wastewater using spruce sawdust and lignin at two different temperatures. The decolorization yields were calculated as the final values. Increasing the temperature during adsorption leads to higher decolorization yields, which may be due to the fact that some substances react only at elevated temperatures. The results of this research are useful for the treatment of industrial wastewater in paper mills, and the waste black liquor (alkaline lignin) can be used as a biosorbent.

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.

Enhanced photocatalytic degradation of Reactive Red 120 dye under solar light using BiPO4@g-C3N4 nanocomposite photocatalyst

Azo dyes such as Reactive Red 120 raise great concerns about their increased harmfulness. Photocatalytic degradation is considered to be one of the most efficient techniques for Reactive Red 120 degradation. Herein, a highly solar active graphitic carbon nitride-assisted bismuth phosphate nanocomposite (BiPO₄@g-C₃N₄) was synthesized by the thermal decomposition of melamine followed by the co-precipitation method. Various analytical techniques were utilized to characterize the prepared BiPO₄, g-C₃N₄, and BiPO₄@g-C₃N₄ nanocomposites. Scanning electron microscopy (SEM) shows the nanorods and particle morphology of the bare BiPO₄ and g-C₃N₄ respectively. Furthermore, the optical band gap energies of the BiPO₄, g-C₃N₄, and BiPO₄@g-C₃N₄ nanocomposite have been calculated to be 4.20, 2.66, and 2.68 eV respectively. Under sunlight, the BiPO₄@g-C₃N₄ nanocomposite showed higher photocatalytic activity towards the degradation of RR120. The BiPO₄@g-C₃N₄ nanocomposite efficiently degrades the RR120 under sunlight with a higher first-order reaction rate constant of 0.0145 min^-1. This is seven times higher than that of bare BiPO₄ (0.0019 min^-1) nanorods and four times greater than g-C₃N₄ (0.0036 min^-1). The photocatalytic efficiency was found to be maximum at pH 4 and decreased as the pH of the solution increased. Even after five recycle runs, the catalyst performance of the RR120 dye has decreased by less than 5%, indicating the high stability of the BiPO₄@g-C₃N₄ nanocomposite. Furthermore, the radical trapping experiment demonstrates that the active species in the dye degradation process are holes and hydroxide radicals. The photocatalytic mechanism was proposed for the BiPO₄@g-C₃N₄ nanocomposite and further validated by the electrochemical impedance spectroscopy analysis.

Regeneration of dye-saturated activated carbon through advanced oxidative processes: A review

Activated carbon (AC) is a porous carbon-rich material that is widely used to remove pollutants, such as synthetic dyes, from contaminated water. Although quite efficient, the use of this technology is limited to the ability of the AC to be regenerated and/or reused. Conventional regeneration procedures are inefficient, requiring the development and/or implementation of new approaches. Advanced Oxidative Processes (AOP) have unique properties that result in high efficiency in wastewater treatment. The use of these technologies in the regeneration of AC has gained considerable prominence due to the ability to remove organic pollutants concentrated in the AC. During this process, the oxidizing species produced interact with the substrates adsorbed on the AC, in a non-selective way, mineralizing them and/or reducing their recalcitrance. Although widely used in wastewater treatment, few reviews focus on the use of AOP as AC regeneration technology, causing an insufficient exchange of information and ideas for strategic development in this area. Therefore, in this review, the authors present an overview of the use of some AOP (Photolysis, Peroxidation, Fenton reaction and Advanced electrochemical oxidative processes) when applied in regeneration of dye-saturated AC, including the mechanisms involved in the different processes, the general aspects that affect individual processes and the different methods established to quantify the effectiveness of regeneration.

Green products from herbal medicine wastes by subcritical water treatment

Herbal medicine wastes (HMWs) are byproducts of medicine factories, which are mainly landfilled for their environmental problems. Only bearing in mind the contamination and concerns caused by the COVID-19 pandemic and environmental emissions, the worth of herbal medicine wastes management and conversion to green products can be understood. In this work, subcritical water treatment was carried out batch-wise in a stainless tube reactor in the pressure range of 0.792-30.0 MPa, varying the temperature (127-327 °C) and time (1-60 min) of extraction. This resulted in new and green material sources, including organic acids, amino acids, and sugars. Amazingly, at very low extraction times (below 5 min) and high temperatures (above 277 °C), about 99% of HMWs were efficaciously converted to clean products by subcritical hydrothermal treatment. The results of hydrothermal extraction after 5 min indicated that at low temperatures (127-227 °C), the total organic carbon in the aqueous phase increased as the residual solid phase decreased, reaching a peak around 220 °C. Acetone soluble extracts or fat phase appeared above 227 °C and reached a maximum yield of 21% at 357 °C. Aspartic acid, threonine, and glycine were the primary amino acids; glycolic acid, formic acid, lactic acid, and acetic acid were obtained as the main organic acids, glucose, fructose, and cellobiose were substantial sugars produced from the aqueous phase after 5 min of hydrothermal subcritical hydrolysis extraction.

Improvement of endoglucanase production by Aspergillus brasiliensis in solid-state fermentation using cupuaçu (Theobroma grandiflorum) residue as substrate

AIMS

Optimize the production of Aspergillus brasiliensis endoglucanase in a solid-phase bioprocess using cupuaçu shell as substrate.

METHODS AND RESULTS

The shells were supplemented with nitrogen and phosphorous and used as a substrate. The centesimal and inorganic composition of the residue was determined, and found to be rich in fibres, and possessed essential elements for fungal growth. In the initial cultivation of A. brasiliensis, endoglucanase activity of 7.35 U g^-1 was obtained. A factorial experimental design was used to determine the most significant variables for the bioprocess. The interactions between moisture, temperature and nitrogen source were noteworthy (p < 0.05). From the rotational central composite design, the optimization of temperature and nitrogen supplementation was obtained, and this reached 40.50 U g^-1 , which is an increase of more than five times the value obtained initially. The enzymatic extract was applied as the biocatalyst in the hydrolysis of cupuaçu shells and, after 48 h, it was possible to observe the production of reducing sugars.

CONCLUSIONS

Cupuaçu shell can be used as a substrate for endoglucanase production by A. brasiliensis. The process was optimized for the cultivation temperature and the nitrogen source. The enzymatic extract can be applied in the hydrolysis of lignocellulosic biomass.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cupuaçu shells can be used to produce cellulases, a product of high added value that can generate economic and environmental benefits for communities and companies producing derivatives of the cupuaçu fruit.

Adsorption of Reactive Red 195 from aqueous medium using Lotus (Nelumbo nucifera) leaf powder chemically modified with dimethylamine: characterization, isotherms, kinetics, thermodynamics, and mechanism assessment

NOVELTY STATEMENT

In the modern era, dyes are inevitable and their surging usage leads to colossal contamination of aqueous streams, thereby threatening both the land and aquatic species. One among such dye is anionic Reactive Red 195 (RR 195), and traceable even at minute concentrations of aqueous streams, posing a severe threat to living species. Moreover, RR 195 is highly recalcitrant offering resistance to biodegradation due to the presence of an azo (-N=N-) group within its structure. Thus, there is a definite need to address the issue of eliminating RR 195 from industrial wastewater effluents. In lieu of this, the primitive objective of this study is to test the effectiveness of the natural adsorbent lotus leaf (Nelumbo nucifera) for the selective sorption of RR 195 from the aqueous stream. Although ample literature is available on the direct utilization of lotus leaf as adsorbent, yet no study was performed on the chemical modification (dimethylamine) of the aforementioned adsorbent. Hence, an attempt has been made in this direction to add a new sorbent into the adsorbents database.

Evaluation of Cocoa Beans Shell Powder as a Bioadsorbent of Congo Red Dye Aqueous Solutions

The use of synthetic dyes in the textile, leather, and paper industries is a source of groundwater pollution around the world. There are different methods for the treatment of wastewater that has been contaminated with dyes, among which adsorption with agro-industrial wastes is gaining relevance. In the present study, the adsorption capacity of cocoa bean shell powder was evaluated when it was used as a bioadsorbent for Congo red dye in an aqueous medium. A 2⁴ central factorial design with central and axial points was proposed to determine the adsorption capacity. The factors that were studied were the adsorbent (0.06–0.15 g), Congo red (40–120 mg L⁻¹), pH (3–11), and time (4–36 h). The bioadsorbent was characterized through scanning electron microscopy and Fourier-transform infrared spectroscopy. The effects of the factors on the adsorption capacity for Congo red using cocoa bean shell were nonlinear, and they were modeled with a second-order polynomial (p < 0.05) and with an R² of 0.84. The bioadsorbent obtained a maximum adsorption of 89.96% in runs. The process of optimization by using the surface response allowed the maximization of the adsorption, and the validation showed that 95.79% adsorption of the dye was obtained.

Elimination of basic blue 9 by electrocoagulation coupled with pelletized natural dead leaves (Sapindus mukorossi) biosorption

Elimination of basic blue 9 (BB-9), a cationic textile dye, by electrocoagulation coupled with biosorption exploiting pelletized natural dead leaves (PNDL) of Sapindus mukorossi, an economic alternative biosorbent, was investigated. The experimental runs were conducted in a laboratory-scale hybrid reactor loaded with Al electrodes, aeration spargers and PNDL packed twin suspended buckets. The pelletized adsorbents offer key advantages of good mechanical stability, lesser clogging risk, and easy disengagement as compared to powdered adsorbents. The parameters of current density, pH, PNDL dose, and initial dye concentration were studied for the decolorization and COD removal efficiency. The experimental results revealed that up to 99.9% decolorization and 90.01% COD removal efficiency achieved after 8 min at optimum condition of current density (j)=20.27 mA/cm², pH = 9, PNDL dose = 6 g/L, and initial dye concentration = 50 mg/L. The BB-9 elimination followed the first-order kinetics with K₁=0.318 min^-1 and R²=0.997. The results revealed the potential of PNDL as a feasible biosorbent with the effective performance of the coupled process.

Modeling the removal of Reactive Red 120 dye from aqueous effluents by activated carbon

The adsorption isotherms of Reactive Red 120 (RR-120) on Brazilian pine-fruit shell activated carbon, at six temperatures (298, 303, 308, 313, 318 and 323 K) and pH = 6, were determined and interpreted using a double layer model with one energy. A statistical physics treatment established the formulation of this model. Steric and energetic parameters related to the adsorption process, such as the number of adsorbed molecules per site, the receptor sites density and the concentration at half-saturation, have been considered. Thermodynamic potential functions such as entropy, internal energy and Gibbs free enthalpy are analyzed, and the choice of the models is based on assumptions in correlation with experimental conditions. By numerical fitting, the investigated parameters were deduced. The theoretical expressions provide a good understanding and interpretation of the adsorption isotherms at the microscopic level. We believe that our work contributes to new theoretical insights on the dye adsorption in order to know the physical nature of the adsorption process.

Upgrading of agro-industrial green biomass residues from chocolate industry for adsorption process: diffusion and mechanistic insights

In the last decades, the world suffers from the wastes those results from unprecedented growth in the food industry. This context investigated the characteristics and suitability of utilizing cocoa shell (CS), an agro-industrial residual biomass waste from the chocolate industry, without any chemical and/or physical treatment. It is an abundant, low-cost, and green adsorbent that can be utilized for the effective removal of basic blue (BB41) as an example of cationic dye from aqueous solutions. The CS showed high adsorption potential (90.04%) with the mild operating condition, 45 min adsorption time, pH 6, CS dose 4 g/L, BB41 concentration 10 mg/L, stirring speed 400 rpm at 295 K. The kinetic, equilibrium, isotherms and mechanism studies revealed that the BB41 adsorption onto CS was attained mainly by electrostatic interaction, π-π stacking interaction, hydrogen bonding, covalent bond, and physical mechanisms. Besides, the organic functional groups played an important role during the adsorption process. The thermodynamic parameters suggested that the adsorption of BB41 dye was the non-spontaneous endothermic process with an activation energy 18.28 kJ/mol. From the industrial point of view, this work offers an economical push in waste management and also a green approach for the effective removal of toxic dyes from textile wastewater.

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.

Textile finishing dyes and their impact on aquatic environs

In the present review, we have been able to describe the different families of dyes and pigments used in textile finishing processes (Yarns, fabrics, nonwovens, knits and rugs) such as dyeing and printing. These dyes are reactive, direct, dispersed, indigo, sulphur and vats. Such that their presence in the liquid effluents resulting from the textile washing constitutes a serious risk, in the absence of their purification, for the quality of receiving aquatic environments. Indeed, the presence of these dyes and pigments can cause a significant alteration in the ecological conditions of the aquatic fauna and flora, because of the lack of their biodegradability. This has a negative impact on the equilibrium of the aquatic environment by causing serious dangers, namely the obvious dangers (Eutrophication, under-oxygenation, color, turbidity and odor), the long-term dangers (Persistence, bioaccumulation of carcinogenic aromatic products and formation of by-products of chlorination), mutagenicity and carcinogenicity.

A passively immobilized novel biomagsorbent for the effective biosorptive treatment of dye contamination

A new magnetic bio-based composite was designed by the magnetic modification of passively immobilized fungal cells. It was utilized for biosorptive decolorization of reactive dye-contaminated aquatic media. As a greener option, waste tea leaf tissues were used for the first time as an immobilization matrix for microbial cells. Immobilized magnetic cells (biomagsorbent) could be effectively used in both batch and dynamic flow mode treatment processes and real environmental application. Rapid equilibrium and high decolorization yields were observed for the target dye (reactive violet 1). The temperature did not significantly affect the process. Langmuir and the pseudo-second-order models could be better used to fit the process equilibrium and kinetics, respectively. Maximum monolayer sorption capacity was 152.88 mg g^-1. High biosorption and desorption yields for 50 consecutive dynamic flow decolorization cycles were recorded as striking results. The breakthrough time was 3420 min. Simulated and industrial water treatment performance of biomagsorbent was found to be more than 90%. The mechanism was evaluated by IR and zeta potential analysis. The magnetic character of the sorbent provided good mechanical durability, easy separation, and excellent regeneration ability. Consequently, this work provides new insight into scalar enhancement of water treatment.

Using modified fish scale waste from Sardinella brasiliensis as a low-cost adsorbent to remove dyes from textile effluents

Textile industry wastewater has become a cause of concern to environmentalists due to its toxic composition and the difficulty of breaking down certain dyes. In this study, modified fish scales of Sardinella brasiliensis (SSb) were used as an alternative for a low-cost adsorbent to remove dyes from textile wastewaters. Adsorption efficiency was assessed by measuring the general, kinetic, and thermodynamic physico-chemical parameters of adsorption isotherms, using Reactive Turquoise Blue 15 (RTB15) and Reactive Red 120 (RR120) dyes as adsorbate models, as local textile industries commonly use these dyes. The isothermal data from the batch experiments were inserted in the Langmuir, Freundlich, and Langmuir-Freundlich (SIPS) equations; the Langmuir isotherm equation showed the most appropriate. The thermodynamic parameters showed that adsorption of dyes by the modified SSb adsorbent was an endothermic yet spontaneous process in the case of RR120. Sorbent-based on SSb material was concluded as adsorbing both of the tested dyes. Because of its abundant availability, and the small amount of activation needed to turn it into an adsorbent, this biowaste can be employed as a low-cost alternative for removal of dyes in the treatment of textile wastewater.

Supercritical Fluid Extraction of Fat and Caffeine with Theobromine Retention in the Cocoa Shell

The cocoa shell is a residue of low commercial value, which represents an alternative for obtaining substances of added value for the food and pharmaceutical industry. Substances of interest in the shell include fat and methylxanthines (theobromine and caffeine). In order to obtain the extraction behavior with supercritical CO2, a 23 factorial design was proposed with six central points, taking dynamic extraction into consideration. The following factors were involved: pressure (2,000–6,000 psi), temperature (313–333 K), and time (30–90 min). The obtained yield was between 3.66% and 15.30%. Fat was the substance that was extracted most effectively (94.73%). Caffeine demonstrated variability in the residue, with at least six treatments that exceeded a removal rate of more than 90%, while it was practically impossible to extract theobromine. The difference with regard to the extraction of theobromine may be attributed to its low solubility. Characterization using FT–IR showed the modifications before and after the process, providing clear evidence of the changes corresponding to the fat at 2,924, 2,854 and 1,745 cm−1. The results presented establish the basis for the extraction of substances such as fats and methylxanthines from a cocoa shell with the use of CO2.

Adsorption of Rhodamine B dye from aqueous solution onto acid treated banana peel: Response surface methodology, kinetics and isotherm studies

The adsorption of rhodamine B (RhB) using acid modified banana peels has been examined. Chemical characteristics of the adsorbents were observed in order to determine active functional groups. The major functional groups on the surface were OH, C = O, C = C and C-O-C. Interactions between operational parameters were studied using the central composite design (CCD) of response surface methodology (RSM). The predictions of the model output indicated that operational factors influenced responses at a confidence level of 95% (P<0.05). The optimum conditions for adsorption were pH 2 at a 0.2 g/L dose within 60 minutes of contact time. Isotherm studies were carried out using the optimized process variables. The data revealed that RhB adsorption fitted the Langmuir isotherm equation while the reduction of COD followed the Freundlich isotherm. Kinetic experiments fitted the pseudo second order model for RhB removal and COD reduction. The adsorption mechanism was not the only rate controlling step. Diffusion through the boundary layer described the pattern of adsorption.

Hierarchically porous poly(ethylenimine) modified poly(styrene-co-divinylbenzene) microspheres for the adsorption of gold nanoparticles and simultaneously being transformed as the nanoparticles immobilized catalyst

With the extensive applications of gold nanoparticles (AuNPs) and the confirmation of their toxicity on human health and environment, it was urgent to remove AuNPs from environment. The hierarchically porous poly(ethylenimine) modified poly(styrene-co-divinylbenzene) microsphere (PEI-PS-DVB) was prepared and characterized by scanning electron microscopy, X-ray diffraction, transform infrared spectrometry, energy dispersive X-ray spectrometry, elemental analysis, contact angle, zeta potential analysis, N₂ adsorption-desorption and mercury intrusion porosimetry. PEI-PS-DVB possessed abundant flow-through pores (70-120 nm) and meso/micropores (<50 nm); the former pores enabled full availability of the adsorbent to relatively large adsorbate, i.e. AuNPs, with fast mass transfer, while the latter ones ensured large surface area for high adsorption capacity. Thanks to its plentiful nitrogen and special hierarchical pores, PEI-PS-DVB was suitable for the adsorption of AuNPs by electrostatic interaction and special affinity between nitrogen and Au. The adsorption obeyed the pseudo-first-order kinetic and Langmuir isotherm models. The maximum adsorption capacity based on Langmuir model was 806.5 mg/g. Moreover, PEI-PS-DVB adsorbing AuNPs could be the efficient catalyst for the reduction of 4-nitrophenol with satisfactory reusability. The developed hierarchically porous PEI-PS-DVB was a promising adsorbent for AuNPs with high adsorption capacity, and recycling usage of waste AuNPs conformed to the green and sustainable concept.

Biosorption of reactive yellow dye by malt bagasse

This research evaluated the biosorption potential of the 134% Yellow Reafix BR2 dye by the malt bagasse. Tests were conducted at batch conditions, under controlled agitation, pH, and temperature. The biosorbent was characterized through scanning electron microscopy and Fourier transform infrared spectroscopy, before and after biosorption. Malt bagasse presented a point of zero charge at 6.75. In the process variables evaluation, there was a greater biosorption potential in acidic pH, without a significant influence of size on the biosorbent particles. The equilibrium time was achieved in 360 min, with approximately 93% removal at the evaluated temperatures. The experimental data were best represented by the pseudo-second-order model. Biosorption was characterized as spontaneous and endothermic, with indicative of physical. Considering the equilibrium, the Langmuir isotherm was the one that best fit the experimental data, with a maximum biosorption capacity of 68.75 mg g–1 (at 303 K and pH 2). The removal suffered no significant interference with the presence of another dye nor with the increase of ionic strength. Thus, the malt bagasse shows potential to be used as a biosorbent in treatment systems of industrial effluents.

Exploring the Reusability of Synthetically Contaminated Wastewater Containing Crystal Violet Dye using Tectona grandis Sawdust as a Very Low-Cost Adsorbent

Present investigation explores the possible reusability of synthetically contaminated wastewater containing crystal violet (CV) organic dye using Tectona grandis sawdust (TGSD) waste as a very low-cost adsorbent. The adsorbent was characterized by proximate, SEM/EDX, FTIR, and XRD analyses. Batch adsorption studies were carried under changing conditions of contact time, the initial concentration of CV, pH, TGSD dose, TGSD particle size, and temperature. The experimental data were tested using Langmuir, Freundlich and Temkin isotherm models, and the data were best followed by Langmuir one. The kinetic results were examined in the light of different models and pseudo-second-order was obtained to be best obeyed. The values of ΔH° (28.642 kJ/mol), ΔG° (-10.776 to -7.080 kJ/mol) and ΔS° (121.8 J/K/mol) in the temperature range of 293-323 K suggested the overall process to be spontaneous, endothermic and associated with an increase in randomness. On the basis of experimental results and their analyses, it has been established that TGSD is one of the most effective adsorbents among those obtained from the domestic, agricultural and industrial wastes. Thus this adsorbent can be effectively utilized to make the impure wastewater reusable.

Sorptive removal of phenanthrene from aqueous solutions using magnetic and non-magnetic rice husk-derived biochars

A magnetically modified rice husk biochar (MBC) was successfully prepared by a hydrothermal method from original biochar (BC) and subsequently used to remove phenanthrene (PHE) from aqueous solutions. The porosity, specific surface area and hydrophobicity of BC were significantly improved (approx. two times) after magnetic modification. The adsorption data fitted well to pseudo-second-order kinetic and Langmuir models. Compared with BC, MBC had a faster adsorption rate and higher adsorption capacity of PHE. The adsorption equilibrium for PHE on MBC was achieved within 1.0 h. The maximum adsorption capacity of PHE on MBC was 97.6 mg g^-1 based on the analysis of the Sips model, which was significantly higher than that of other sources of BCs. The adsorption mechanism of the two BCs was mainly attributed to the action of surface functional groups and π-π-conjugated reactions. The adsorption of PHE on MBC mainly occurred in the functional groups of C-O and Fe₃O₄, but that on BC was mainly in the functional groups of -OH, N-H, C=C and C-O.

Modifying cellulose with metaphosphoric acid and its efficiency in removing brilliant green dye

In this study, cellulose was chemically modified through the addition of the phosphorylating agent, metaphosphoric acid in order to obtain a new material (MPCel) with higher adsorptive properties than the starting material. Both materials were characterized by infrared spectroscopy, X-ray diffraction, solid-state phosphorus-31 nuclear magnetic resonance spectroscopy and thermogravimetric analysis. Maximal adsorption capacity, at 45°C for pure cellulose, was 90.5mgg^-1, at pH=10 and contact time of 40min, with experimental isotherms better adjusted to the Langmuir model. MPCel at the same temperature conditions showed contact time of 10min, pH=10, and maximal adsorption capacity of 150.0mgg^-1, being better adjusted to the Temkin model. The kinetic study of both materials followed the pseudo-second-order model. Modification successfully occurred and both adsorbents were shown able to be capable of removing the brilliant green dye, but MPCel was more efficient for purpose, when compared to the pure cellulose.

Chemically Modified Polyvinyl Chloride for Removal of Thionine Dye (Lauth's Violet)

The chemical modification of hydrophobic polymer matrices is an alternative way to elchange their surface properties. The introduction of sulfonic groups in the polymer changes the surface properties such as adhesion, wettability, catalytic ability, and adsorption capacity. This work describes the production and application of chemically modified polyvinyl chloride (PVC) as adsorbent for dyes removal. Chemical modification of PVC was evaluated by infrared spectroscopy and elemental analysis, which indicated the presence of sulfonic groups on PVC. The chemically modified PVC (PVCDS) showed an ion exchange capacity of 1.03 mmol⁻¹, and efficiently removed the thionine dye (Lauth’s violet) from aqueous solutions, reaching equilibrium in 30 min. The adsorption kinetics was better adjusted for a pseudo second order model. This result indicates that the adsorption of thionine onto PVCDS occurs by chemisorption. Among the models for the state of equilibrium, SIPS and Langmuir exhibited the best fit to the experimental results and PVCDS showed high adsorption capacities (370 mg⁻¹). Thus, it is assumed that the system presents homogeneous characteristics to the distribution of active sites. The modification promoted the formation of surface characteristics favorable to the dye adsorption by the polymer.

Kinetics, isotherm, and thermodynamic studies of methylene blue adsorption from water by Mytella falcata waste

This work evaluates the application of Mytella falcata shells, discarded in large quantities in the state of Alagoas, Brazil, as adsorbent for methylene blue dye (MB). It was investigated how the amount of adsorbent (M), the average particle diameter (G), and the agitation speed (A) affected the adsorption. Kinetic and equilibrium studies were conducted, and the pseudo-second-order equation adequately represented the kinetic data and isotherms following Liu's model (q _max = 8.81 mg g^-1 at 60 °C). The adsorption was spontaneous, favorable, and endothermic. Mytella falcata shell is a suitable adsorbent for MB and could potentially contribute to its removal from the environment.

Eragrostis plana Nees as a novel eco-friendly adsorbent for removal of crystal violet from aqueous solutions

Eragrostis plana Nees (EPN) was used as new and eco-friendly adsorbent for the removal of crystal violet dye (CV) from aqueous solution. Specific surface area (BET), scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), point of zero charge (pH_PZC), and modified Boehm titration method were used to characterize the EPN material. The effects of initial pH of solution, adsorbent mass, contact time and initial dye concentration, and temperature were studied in batch adsorption mode. Kinetic data were evaluated by pseudo-first-order and pseudo-second-order models. The result exhibited that pseudo-second-order model well described the adsorption kinetics of CV onto EPN. Langmuir, Freundlich, and Sips isotherm models were used for analysis of the isothermal data. The equilibrium data of adsorption of CV onto EPN was better fitted with the Sips isotherm. Based on the Sips isotherm model, the maximum adsorption capacity was 76.20 ± 1.20 mg g^-1 at 333 K. A high desorption of CV from EPN was obtained using 1.00 mol L^-1 of CH₃COOH as eluent. The thermodynamic data indicated that the adsorption was spontaneous, endothermic, and physical process. EPN can be used as alternative adsorbent to remove CV from aqueous solution.

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

Removal of cationic dye, Azur II, and anionic dye, Reactive Red 2 (RR-2) from aqueous solutions, has been successfully achieved by using a modified agricultural biomaterial waste: cocoa shell husk (Theobroma cacao) treated by gliding arc plasma (CPHP). The biomass in its natural form CPHN and modified form CPHP was characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and point of zero charge (pH_pzc). Experimental variables such as initial pH, contact time, and temperature were optimized for adsorptive characteristics of CPHN and CPHP. The results show that the removal of the Azur II dye was favorable in the basic pH region (pH 10) while the Reactive Red 2 dye was favorable in the acidic pH region (pH 2). The minimum equilibrium time for Azur II and RR-2 dye was obtained after 40 and 240 min, respectively. The adsorption kinetics and isotherm data obtained were best described by a pseudo-second-order kinetic rate model and a combination of Langmuir-Freundlich isotherm models. This work indicates that the plasma-treated raw materials are good alternative multi-purpose sorbents for the removal of many coexisting pollutants from aqueous solutions.