Egg By-Products as a Tool to Remove Direct Blue 78 Dye from Wastewater: Kinetic, Equilibrium Modeling, Thermodynamics and Desorption Properties

A Comprehensive Strategy for Stepwise Design of a Lab PROTOTYPE for the Removal of Emerging Contaminants in Water Using Cyclodextrin Polymers as Adsorbent Material

The significant environmental issue of water pollution caused by emerging contaminants underscores the imperative for developing novel cleanup methods that are efficient, economically viable, and that are intended to operate at high capacity and under continuous flows at the industrial scale. This study shows the results of the operational design to build a prototype for the retention at lab scale of pollutant residues in water by using as adsorbent material, insoluble polymers prepared by β-cyclodextrin and epichlorohydrin as a cross-linking agent. Laboratory in-batch tests were run to find out the adsorbent performances against furosemide and hydrochlorothiazide as pollutant models. The initial evaluation concerning the dosage of adsorbent, pH levels, agitation, and concentration of pharmaceutical pollutants enabled us to identify the optimal conditions for conducting the subsequent experiments. The adsorption kinetic and the mechanisms involved were evaluated revealing that the experimental data perfectly fit the pseudo second-order model, with the adsorption process being mainly governed by chemisorption. With KF constant values of 0.044 (L/g) and 0.029 (L/g) for furosemide and hydrochlorothiazide, respectively, and the determination coefficient (R2) being higher than 0.9 for both compounds, Freundlich yielded the most favorable outcomes, suggesting that the adsorption process occurs on heterogeneous surfaces involving both chemisorption and physisorption processes. The maximum monolayer adsorption capacity (qmax) obtained by the Langmuir isotherm revealed a saturation of the β-CDs-EPI polymer surface 1.45 times higher for furosemide (qmax = 1.282 mg/g) than hydrochlorothiazide (qmax = 0.844 mg/g). Based on these results, the sizing design and building of a lab-scale model were carried out, which in turn will be used later to evaluate its performance working in continuous flow in a real scenario.

One-step synthesis of magnetic fly ash composites for methylene blue removal: batch and column study

This study focuses on the synthesis of magnetic fly ash composites and its application for the removal of methylene blue (MB) from wastewater. By-product of oil power plants, oil fly ash, was treated with magnetic nanoparticles after chemical surface modification and dubbed modified fly ash (MFA). MFA was characterized by X-ray fluorescence, diffractogram analysis, scanning electron microscopy, energy-dispersive X-ray (EDX), and Fourier transform infrared (FT-IR) and N2 physisorption. MB (methylene blue) was removed from an aqueous solution using the response surface modelling (RSM) technique, which was used for optimization reasons. All four independent factors were investigated to see how they affected the removal process: adsorbent dosage; contact time; pH; and beginning dye concentration. The rate of MB removal was strongly influenced by the pH of the solution. The Langmuir and Freundlich models were used to examine equilibrium data A for MB adsorption onto the MFA in linear and nonlinear forms. Langmuir gave a better fit. The adsorption kinetics shown by increased kinetic statistics were better characterized by a pseudo-second-order MFA model. As far as thermodynamic characteristics go, adsorption is endothermic and occurs spontaneously. It has been proven that MFA may be used as an adsorbent to remove MB dye with high efficiency, and the quadratic model has been proved to be statistically significant.

Synthesis and Assessment of Antimicrobial Composites of Ag Nanoparticles or AgNO3 and Egg Shell Membranes

Engineering research has been expanded by the advent of material fusion, which has led to the development of composites that are more reliable and cost-effective. This investigation aims to utilise this concept to promote a circular economy by maximizing the adsorption of silver nanoparticles and silver nitrate onto recycled chicken eggshell membranes, resulting in optimized antimicrobial silver/eggshell membrane composites. The pH, time, concentration, and adsorption temperatures were optimized. It was confirmed that these composites were excellent candidates for use in antimicrobial applications. The silver nanoparticles were produced through chemical synthesis using sodium borohydride as a reducing agent and through adsorption/surface reduction of silver nitrate on eggshell membranes. The composites were thoroughly characterized by various techniques, including spectrophotometry, atomic absorption spectrometry, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, as well as agar well diffusion and MTT assay. The results indicate that silver/eggshell membrane composites with excellent antimicrobial properties were produced using both silver nanoparticles and silver nitrate at a pH of 6, 25 °C, and after 48 h of agitation. These materials exhibited remarkable antimicrobial activity against Pseudomonas aeruginosa and Bacillus subtilis, resulting in 27.77% and 15.34% cell death, respectively.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Removal of an Azo Dye from Wastewater through the Use of Two Technologies: Magnetic Cyclodextrin Polymers and Pulsed Light

Water pollution by dyes is a huge environmental problem; there is a necessity to produce new decolorization methods that are effective, cost-attractive, and acceptable in industrial use. Magnetic cyclodextrin polymers offer the advantage of easy separation from the dye solution. In this work, the β-CD-EPI-magnetic (β-cyclodextrin-epichlorohydrin) polymer was synthesized, characterized, and tested for removal of the azo dye Direct Red 83:1 from water, and the fraction of non-adsorbed dye was degraded by an advanced oxidation process. The polymer was characterized in terms of the particle size distribution and surface morphology (FE-SEM), elemental analysis (EA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), infrared spectrophotometry (IR), and X-ray powder diffraction (XRD). The reported results hint that 0.5 g and pH 5.0 were the best conditions to carry out both kinetic and isotherm models. A 30 min contact time was needed to reach equilibrium with a qmax of 32.0 mg/g. The results indicated that the pseudo-second-order and intraparticle diffusion models were involved in the assembly of Direct Red 83:1 onto the magnetic adsorbent. Regarding the isotherms discussed, the Freundlich model correctly reproduced the experimental data so that adsorption was confirmed to take place onto heterogeneous surfaces. The calculation of the thermodynamic parameters further demonstrates the spontaneous character of the adsorption phenomena (ΔG° = −27,556.9 J/mol) and endothermic phenomena (ΔH° = 8757.1 J/mol) at 25 °C. Furthermore, a good reusability of the polymer was evidenced after six cycles of regeneration, with a negligible decline in the adsorption extent (10%) regarding its initial capacity. Finally, the residual dye in solution after treatment with magnetic adsorbents was degraded by using an advanced oxidation process (AOP) with pulsed light and hydrogen peroxide (343 mg/L); >90% of the dye was degraded after receiving a fluence of 118 J/cm2; the discoloration followed a pseudo first-order kinetics where the degradation rate was 0.0196 cm2/J. The newly synthesized β-CD-EPI-magnetic polymer exhibited good adsorption properties and separability from water which, when complemented with a pulsed light-AOP, may offer a good alternative to remove dyes such as Direct Red 83:1 from water. It allows for the reuse of both the polymer and the dye in the dyeing process.

Advanced graphene oxide-based membranes as a potential alternative for dyes removal: A review

Graphene oxide (GO) is one of the most well-known graphene derivatives which, due to its outstanding chemical, electrical and optical properties as well as its high oxygen content, has been recently applied in several fields such as in the construction of sensors, as antimicrobial agent for biomedical applications, as well as nanofiller material for membranes applied in wastewater treatment. In this last-mentioned field, the synthesis and functionalization of membranes with GO has proven to improve the performance of membranes applied in the treatment of wastewater containing dyes, regarding antifouling behavior, selectivity and flux. In this review, an overview of water pollution caused by effluents containing synthetic dyes, the advantages and limitations of GO-based membranes and the latest research advances on the use of GO-based membranes for dyes removal, including its impact on membrane performance, are discussed in detail. The future panorama of the applicability of GO-based membranes for the treatment of water contaminated by dyes is also provided.

Factors Affecting Synthetic Dye Adsorption; Desorption Studies: A Review of Results from the Last Five Years (2017-2021)

The primary, most obvious parameter indicating water quality is the color of the water. Not only can it be aesthetically disturbing, but it can also be an indicator of contamination. Clean, high-quality water is a valuable, essential asset. Of the available technologies for removing dyes, adsorption is the most used method due to its ease of use, cost-effectiveness, and high efficiency. The adsorption process is influenced by several parameters, which are the basis of all laboratories researching the optimum conditions. The main objective of this review is to provide up-to-date information on the most studied influencing factors. The effects of initial dye concentration, pH, adsorbent dosage, particle size and temperature are illustrated through examples from the last five years (2017-2021) of research. Moreover, general trends are drawn based on these findings. The removal time ranged from 5 min to 36 h (E = 100% was achieved within 5-60 min). In addition, nearly 80% efficiency can be achieved with just 0.05 g of adsorbent. It is important to reduce adsorbent particle size (with Φ decrease E = 8-99%). Among the dyes analyzed in this paper, Methylene Blue, Congo Red, Malachite Green, Crystal Violet were the most frequently studied. Our conclusions are based on previously published literature.

Modified wheat straw-derived graphene for the removal of Eriochrome Black T: characterization, isotherm, and kinetic studies

A cost-effective and environment-benign adsorbent was prepared from an abundant agro-waste material. Wheat straw was reduced to graphene and then modified by crosslinking to epichlorohydrin. During the conversion process of wheat straw to graphene, the specific surface area increased more than 100 times (from 4 to 415 m² g^-1). The adsorption efficiency of raw wheat straw, graphene nanosheets, and modified graphene against Eriochrome Black T (EBT) were 8.0, 34.7, and 74.4%, respectively. The modified graphene was further investigated for the effect of environmental condition, i.e., pH (3 to 11), EBT concentration (25-100 mg L^-1), adsorbent dosage (0.25-0.75 g L^-1), contact time (5-60 min), and solution temperature (30-60 °C). The dye removal remained at a high level under a wide range of pH from 3 to 9. The EBT removal decreased from 87.3 to 54.5 by increasing dye concentration and increased from 38.2 to 85.4% by increasing adsorbent dose in the studied ranges. Dye removal also increased by mixing time from 5 to 30 min, whereas a slight drop was observed by continuing agitation up to 60 min. Conducting experiments at various temperatures revealed an endothermic process. Pseudo-first-order and pseudo-second-order models were adequate to represent the adsorption kinetics. Isotherm models suggest a multilayer adsorption of EBT molecules on heterogeneous modified graphene surface with a maximum adsorption capacity of 146.2 mg g^-1. The present work demonstrated that the modified graphene obtained from available and low-cost agro-wastes could be used effectively as adsorbent against EBT from aqueous media.

Recent Achievements in Polymer Bio-Based Flocculants for Water Treatment

Polymer flocculants are used to promote solid-liquid separation processes in potable water and wastewater treatment. Recently, bio-based flocculants have received a lot of attention due to their superior advantages over conventional synthetic polymers or inorganic agents. Among natural polymers, polysaccharides show many benefits such as biodegradability, non-toxicity, ability to undergo different chemical modifications, and wide accessibility from renewable sources. The following article provides an overview of bio-based flocculants and their potential application in water treatment, which may be an indication to look for safer alternatives compared to synthetic polymers. Based on the recent literature, a new approach in searching for biopolymer flocculants sources, flocculation mechanisms, test methods, and factors affecting this process are presented. Particular attention is paid to flocculants based on starch, cellulose, chitosan, and their derivatives because they are low-cost and ecological materials, accepted in industrial practice. New trends in water treatment technology, including biosynthetic polymers, nanobioflocculants, and stimulant-responsive flocculants are also considered.

Synthesis of New Cyclodextrin-Based Adsorbents to Remove Direct Red 83:1

Two cyclodextrins (CDs), γ– and hydroxypropyl (HP)–γ–CDs were used to synthesize new adsorbents by using epichlorohydrin (EPI) as cross-linking agent in order to remove Direct Red 83:1 (DR) from water. Both polymers were characterized in terms of Fourier spectroscopy, nuclear magnetic resonance, particle size distribution and thermogravimetric analysis. Experimental data for both polymers were well fitted to the pseudo-second order and intraparticle diffusion model, indicating that in the adsorption both chemical and physical interactions are essential in the removal of DR. Three different isotherm models were analyzed, concluding that γ–CDs–EPI followed the Temkin isotherm and HP–γ–CDs-EPI the Freundlich isotherm, these results suggested that the adsorption was happening onto heterogeneous surfaces. The results of the Gibbs free energy showed that the adsorption was spontaneous at room temperature. In order to eliminate the remaining dye after the polymer treatment, and advanced oxidation process (AOP) was considered, achieving more than 90% of removal combining both mechanisms.

Novel Bioderived Composites from Wastes

The recycling and reuse of solid wastes can be considered important challenges for civil and environmental applications in the frame of a more sustainable model of development and the consumption of new resources and energy [...].