Adsorption of methylene blue dye from the aqueous solution via bio-adsorption in the inverse fluidized-bed adsorption column using the torrefied rice husk

Methylene blue removal using nano-TiO2/MWCNT/Chitosan hydrogel composite beads in aqueous medium

Dyestuff, one of the most hazardous compounds in terms of threats to people and the environment, is found in wastewater from industrial usage. The removal of Methylene Blue (MB) from a water-based medium has been studied by numerous researchers using a variety of adsorbents. To remove MB from aqueous solution, nano-TiO2/MWCNT/Chitosan hydrogel composite beads (n-TiO2/MWCNT/Cht) were developed in this study using a sol-gel method. This research discusses the characterisation of a new adsorbent substance using Infrared Spectroscopy (FT-IR) analysis and scanning electron microscopy (SEM). The optimal pH, adsorbent dosage, duration, and starting concentration were ascertained by analyzing the removal efficiencies of MB using the batch adsorption method. Adsorption behaviour at the equilibrium state has been investigated using a variety of adsorption isotherms, including Freundlich, Langmuir, and Dubinin-Radushkevich. The Langmuir adsorption isotherm has been useful to clarify adsorption behaviors. nTiO2-Cht/MWCNT had an adsorption capacity of 80.65 mg/g for MB. The pseudo-second-order kinetic model offered the best agreement to the experimental data for the adsorption of MB. Kinetic models of pseudo-first-order and pseudo-second-order were employed to explore the adsorption processes of MB on the n-TiO2/MWCNT/Cht. This study demonstrated the efficiency of n-TiO2/MWCNT/Cht for the removal of MB from a water-based solution.

Methylene blue and Congo red dye elimination from synthetic wastewater using Albizia lebbeck seed pod powder: isotherm and kinetic and mechanistic studies

This research examined the effectiveness of using Albizia lebbeck seed pods (ALB) as an adsorbent to remove dye effluents and clean up wastewater. More specifically, the binding capacity of methylene blue (MB) and Congo red (CR) dyes from aqueous solution using unmodified Albizia lebbeck seed pods (UALB) and citric acid modified Albizia lebbeck seed pods (CALB) were compared. The adsorbents underwent characterization via the use of Fourier transform infrared spectroscopy and scanning electron microscopy. Several operational factors were investigated using batch tests to ascertain their effects. These parameters included pH, adsorbent dose, interaction duration, and initial dye concentration. The residual dye concentrations were determined, and the data generated were fitted to equilibrium and kinetic models. In CALB and UALB, MB adsorption ideal pH values were 10 and 12, whereas CR optimal pH values were 3 and 2. Also, MB and CR equilibrium durations were 360 and 240 min, respectively. Temkin model best described the adsorption in CALB (r 2  = 0.9916, 0.9484) whereas Freundlich worked well for UALB in MB and CR (r 2  = 0.9626, 0.9871). Kinetic modeling of the adsorption data showed that the pseudo-second-order kinetic model provided the best fit (r 2  = 0.9998, 0.9999) for CALB and (r 2  = 1, 0.9992) for UALB for both MB and CR dyes. Maximum adsorption for MB was 9.499 mg/g and for CR it was 8.628 mg/g, and the findings showed a positive linear correlation between the concentration of dye-ions and their adsorption ability. The CALB also demonstrated superior efficacy in the removal of MB (4.661 mg/g) dye relative to CR (4.113 mg/g). The results of this study demonstrate that the use of ALB, in both modified and unmodified forms, is a cost-effective and efficient approach for the removal of MB and CR from the aqueous environment.

Understanding the column and batch adsorption mechanism of pesticide 2,4,5-T utilizing alginate-biomass hydrogel capsule: A computational and economic investigation

Water pollution has remained a pressing concern in recent years, presenting multifaceted challenges in search of effective mitigation strategies. Our study, which targets mitigating pollution caused by 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a significant aquatic pollutant, is innovative in its approach. We have identified adsorption as a promising, cost-effective method for its removal. Our research strategy involves dynamic adsorption utilizing a peristaltic pump and composite beads containing activated carbon and sodium alginate (CA/Alg), a novel combination that mimics industrial processes. To optimize column adsorption, we examine bead stability under varied pH conditions and optimize parameters such as concentration, adsorption time, and pH through batch adsorption experiments, employing experimental design techniques. Additionally, we optimize column adsorption factors, including bead height, circulation time, and flow rate, crucial for process efficiency, and under these optimum conditions (C2,4,5-T = 80 ppm. pH = 2, t = 27h30min, H = 30 cm and D = 0.5 mL/min) the capacity of adsorption equal to 748.25 mg/g. Characterization techniques like SEM, EDX, BET analysis, XRD, and FTIR provide insights into the morphology, composition, surface area (331 m2/g), pore volume (0.11 cm3/g), crystal structure, and functional groups of the CA-P/Alg adsorbent. Theoretical analysis elucidates the adsorption mechanism and interaction with pollutants. Economic analysis, encompassing CAPEX and OPEX estimation, evaluates the feasibility of implementing this cleanup method at an industrial scale, considering initial investment and ongoing operational costs, indicating potential savings of 64 % compared with the activated carbon normally used on the Moroccan market. This comprehensive and innovative approach addresses water pollution challenges effectively while ensuring economic viability for industry-scale implementation.

Novel granular bentonite-carbon sorbents: textural characterization, adsorption-desorption isotherm, kinetics, and cost estimation

This research focuses on the synthesis of novel low-cost granular sorbents based on bentonite clay of the Navbahor deposit, dust fraction of Angren brown coal, and agricultural wastes such as straw and sawdust to meet the internal needs of the Republic of Uzbekistan. The impact of the initial mixture ingredients on the structural and textural properties of bentonite-coal sorbents (BCSs) has been studied using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, optical microscopy, and nitrogen adsorption-desorption analysis. For determining the sorption capacity of BCSs, a standard model substance methylene blue (MB), was applied. It was revealed that the maximum adsorption amount of MB was 5.3 mg∙g-1 during 2 h of contact. Prolonging the contact time to 24 h allowed for more extensive diffusion of dye molecules into the sorbent's pores, increasing the adsorption capacity to 13 mg∙g-1. It was demonstrated that BCSs could be regenerated by strong oxidizing agents such as sulfuric acid and hydrogen peroxide, with sulfuric acid proving more effective. Regeneration fully restores sorption properties, particularly at low dye concentrations (up to 0.2 mg∙ml-1). Despite slight reductions in adsorption capacity over multiple regeneration cycles, the sorbents maintain their structural integrity and durability. It is shown that compared to imported expensive activated carbon, the gross profitability of the in-house production of such granular BCSs within the territory of Uzbekistan increases from 48 to 78%, while the net income increases almost three times.

Expermental investigation on adsorption of methylene blue dye from waste water using corncob cellulose-based hydrogel

Hydrogel from corncob cellulose was synthesized in this investigation. The synthesized Hydrogel was characterized by SEM, XRD, and FTIR instruments. As the results indicate the synthesized hydrogel has required and important features, these suggest the suitability of hydrogel for the adsorption of methylene blue dye (MBD). Three important process variables (dosage, contact time, and initial concentration) with three levels were studied during the adsorption process at 30 °C and neutral pH. The efficiency of hydrogel for adsorption of MBD was determined in each experiment. The experimental results were statistically analyzed and interpreted. The maximum removal efficiency was achieved at 2.22 g/L of dosage, 80.36 min of contact time, and 74.54 mg/L of initial concentration. At this condition, 98.25% of MBD was achieved through experimental tests. Kinetics, isotherm, and thermodynamics studies were performed. Langmuir isotherm is more suitable to describe the adsorption process and the Pseudo second-order kinetic model fits this process. From the thermodynamics studies, all negative values of change in Gibbs free energy (ΔG°), and positive value of change in enthalpy (ΔH°), and change in entropy (ΔS°) indicate that the carried out experimental process is a spontaneous and endothermic. Moreover, the regeneration experiment for adsorbent was performed. The treatment of real textile industry waste water was conducted and the removal efficiency of hydrogel was 64.76%. This removal percentage reduction from sythetic aqueous solution is due to involvement of other pollutants in the real waste water. The synthesized hydrogel adsorbent is suitable up to the third cycle without significant loss in removal efficiency.

Efficient and synergistic treatment of selenium (IV)-contaminated wastewater and mercury (II)-contaminated soil by anaerobic granular sludge: Performance and mechanisms

Wastewater containing selenium (Se) and soil contaminated by mercury (Hg) are two environmental problems, but they are rarely considered for synergistic treatment. In this work, anaerobic granular sludge (AnGS) was used to address both of the aforementioned issues simultaneously. The performance and mechanisms of Se(IV) removal from wastewater and Hg(II) immobilization in soil were investigated using various technologies. The results of the reactor operation indicated that the AnGS efficiently removed Se from wastewater, with a removal rate of 99.94 ± 0.05%. The microbial communities in the AnGS could rapidly reduce Se(IV) to Se0 nanoparticles (SeNPs). However, the AnGS lost the ability to reduce Se(IV) once the Se0 content reached the saturation value of 5.68 g Se/L. The excess sludge of Se0-rich AnGS was applied to remediate soil contaminated with Hg(II). The Se0-rich AnGS largely decreased the percentage of soil Hg in the mobile, extractable phase, with up to 99.1 ± 0.3% immobilization. Soil Hg(II) and Hg0 can react with Se (-II) and Se0, respectively, to form HgSe. The formation of inert HgSe was an important pathway for immobilizing Hg. Subsequently, the pot experiments indicated that soil remediation using Se0-rich AnGS significantly decreased the Hg content in pea plants. Especially, the content of Hg decreased from 555 ± 100 to 24 ± 3 μg/kg in roots after remediation. In summary, AnGS is an efficient and cost-effective material for synergistically treating Se-contaminated wastewater and Hg-contaminated soil.

Sustainable remediation of dye-contaminated wastewater using novel cross-linked Hex-CCP-co-PPT microspheres

The presence of dyes in contaminated water poses substantial dangers to the health of both humans and aquatic life. A process called precipitation polymerization was used to create unique cross-linked hexa-chlorocyclotriphosphazene-co-phenolphthalein (Hex-CCP-co-PPT) microspheres for the purpose of this research. Advanced methods such as X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermogravimetry (DTG) were used to characterise these microspheres. In a simulated solution, the performance of Hex-CCP-co-PPTs as a sorbent for removing MB dye was investigated, and the results showed an unprecedentedly high removal rate of 88.4% for MB. Temperature of 25 °C, a Hex-CCP-co-PPTs dose of 40 mg, an MB concentration of 20 ppm, an MB solution volume of 20 mL, a contact time of 40 min, and a pH of 9 were found to be the optimal experimental conditions. According to the results of the kinetic and adsorption analyses, the PSO and Langmuir adsorption models are the best ones to use. These models favour the chemi-sorption nature and mono-layered adsorption of MB in comparison to Hex-CCP-co-PPTs. Importantly, the thermodynamic analysis demonstrated that the process of removing MB by utilizing Hex-CCP-co-PPTs was endothermic and occurred spontaneously. These findings highlight the potential application of Hex-CCP-co-PPT microspheres in Algal Membrane Bioreactors (AMBRs) for the efficient and sustainable removal of dye from wastewater. This would contribute to the protection of ecosystems as well as the public's health.

Adsorption-photocatalytic degradation abilities of γ-irradiated chitosan-ZnO-AgNP composite for organic dye removal and antibacterial activity

We synthesized a γ-irradiated chitosan-ZnO-AgNPs (ICZA) composite by using a simple hydrogels method. We evaluated its adsorption/photocatalytic degradation abilities for the removal of an organic dye and its antibacterial activity. The XRD, SEM, TEM, EDS, and FTIR techniques were used to characterize the obtained samples. Based on the adsorption and degradation of methylene blue (MB) in the dark and under UV light irradiation, the adsorption and the photocatalytic activity of the as-obtained samples were evaluated. The optimum conditions for synthesizing the composite were as follows: contact time of 210 min, a dosage of 2 g/L, MB concentration of 40 mg/L, and a solution pH of 8.0. The ICZA had a high adsorption capacity, which was suitable for removing MB from the aqueous solutions; it showed a maximum adsorption capacity (qm) of 92.59 mg/g. The fit of the adsorption isotherms with the Langmuir model was satisfactory. The photocatalytic degradation ability of the composite was also better than that of other catalysts in the presence of UV light, with an apparent rate constant (kapp) of 3.08 × 10-2. The synthesized ICZA also showed good antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 12.5 g/mL and 50 g/mL under light-incubation and dark-incubation conditions. Finally, we discussed the hypothesized mechanism of the adsorption/photocatalytic activity and antibacterial activity of the ICZA composite in this study.

Efficient dye removal from industrial wastewater using sustainable activated carbon and its polyamide nanocomposite derived from agricultural and industrial wastes in column systems

Sugar beet crown (SBC) waste was employed to produce sustainable activated carbon (AC) by a thermo-chemical activation procedure using a fixed ratio of H3PO4/SBC (1 : 1 w/w ratio) at 550 °C/2 h. An activated carbon/polyamide nano-composite (AC/PA) was also prepared through the polymerization of the fabricated AC (90%) with polyamide (PA, 10%) synthetic textile waste using a proper dissolving agent at a specified w/w ratio with the employed polymer (formic acid/PA = 82/18%). Both AC and its derivative AC/PA were employed in the remediation of dyes from industrial wastewater in column systems, and their efficiencies were compared at various applied experimental conditions. The adsorption of the industrial dye waste (IDW) was a pH-, flow rate-, and bed thickness-controlled process by the regarded adsorbents. Kinetic studies confirmed the suitability of the Thomas equation over the Yoon and Nelson model in predicting the dynamic adsorption process of IDW by AC and AC/PA as was assured by the close agreement among the calculated and experimental uptake capacities of both adsorbents at the same applied flow rates, suggesting the chemisorption nature of IDW adsorption. Additionally, electrostatic attraction was the leading mechanism of IDW adsorption by AC and AC/PA composite with some advantages of the former over the latter.

Cold plasma-assisted regeneration of biochar for dye adsorption

Environmental remedies, including adsorption-based water purification, are now being asked to meet the requirement for a low-carbon circular economy requiring low energy and low material consumption. In this regard, we tested the possibility of regenerating adsorbents via cold plasma (CP) treatment for less use of adsorbents and no washing solution. In the adsorption of methylene blue (MB) using carbonized rice husk (CRH) and five successive regeneration cycles by CP treatment, the removal efficiencies were maintained at a moderate level (∼70% of the initial performance), unlike five consecutive adsorption without CP treatment (∼9-13% of the initial performance). The regeneration of CRH by CP treatment was also double-checked by the FESEM, EDS, BET, FTIR, XPS, and surface zeta potential measurements. The successfully recovered adsorption capability is related to the remediation of adsorption sites. It is also worth noting that the required power consumption for recycling by CP treatment was about 6.4 times lower than carbonizing new rice husks. This work provides insights into recovering adsorbents using CP without rigorous, costly, and energy-intensive processes.

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.

Column optimization of adsorption and evaluation of bed parameters-based on removal of arsenite ion using rice husk

The objective of this study deals with column optimization of adsorption-based on removal of arsenite ion using rice husk. The parameters affecting the column adsorption study, i.e., influent-concentration, bed depth, and flow rate, were optimized. The range of parameters, i.e., influent-concentration (15-50 mg/L), flow rate (20, 35, 45, and 60 mL/min), and bed depth (15-60 mm), were studied experimentally. Kinetics models Bohart-Adams and Hutchins were studied to measure the amount adsorbed, depth of mass transfer zone, saturated concentration, and time observed at 10% & 90% breakthrough. The percentage amount adsorbed q_m enhanced with enhancement in bed depth but got reduced with influent ions concentration and volumetric flow rate. Established model Bohart-Adams and Hutchins equations were used for calculation of mass transfer zone which came out to be 51 mm. An adsorption capacity (q_m) of 4.5 mg/g for arsenite ions was achieved at optimum parameter values of 60 mm of bed depth, 20 mL/min volumetric flow rate, and 50 mg/L of influent ions concentration. The adsorption bed parameters were also evaluated using Hutchins and Michaels equations. The column study proved rice husk to be a potential adsorbent for the adsorption of arsenite.

Comparative Adsorption Performance of Carbon-containing Hydroxyapatite Derived Tenggiri (Scomberomorini) and Belida (Chitala) Fish Bone for Methylene Blue

The utilization of fishbone as the carbon source for methylene blue adsorption has been successfully studied. Fishbone was prepared from two kinds of fish such as marine fisheries (ex. Tenggiri) and freshwater fisheries (ex. Belida). The carbons were prepared by carbonation of fishbone powder at  500 °C for 2 h. Physical properties of carbons were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), Scanning Electron Microscope (SEM), and hydrophobicity. The carbons were utilized as the adsorbent for removing methylene blue by varying the contact time, initial dye concentration, and temperature. It is concluded that both carbons can very good adsorb the methylene blue. The adsorption performance of carbon (TFC) from Tenggiri fish is better than carbon (BFC) from Belida fish. The adsorption was well fitted with the Langmuir adsorption model (R2 ~ 0.998) and the pseudo-second-order model. This indicated that the dye molecules were adsorbed on the surface-active site of carbon via chemical binding, forming an adsorbate monolayer. Thermodynamic parameters, including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS), indicated that the adsorption of methylene blue onto the carbon from fishbone was spontaneous. Thus, carbon from fishbone can be applied as a low-cost adsorbent to treat industrial effluents contaminated with methylene blue. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Acetaminophen removal by calcium alginate/activated hydrochar composite beads: Batch and fixed-bed studies

The occurrence of acetaminophen in surface water has been reported worldwide, indicating the need of alternative wastewater treatments. Activated hydrochar (AHC) is efficient for pharmaceuticals removal. Powdered AHC presents challenges that hamper its expansion. However, these issues can be overcome by adding polymers, such as alginate, in composite beads. Therefore, the present study aimed to develop and characterize alginate/brewer's spent grain AHC beads, applying them to acetaminophen adsorption in batch and fixed-bed experiments. The adsorbent presented a high surface area (533.42 m² g^-1) and Fourier-transform infrared spectroscopy (FTIR) showed that alginate assigned new functional groups to the composite. Batch studies revealed an endothermic behavior and maximum adsorption capacity of 165.94 mg g^-1, with an equilibrium time of 240 min. The fixed-bed maximum adsorption capacity was 127.01 mg g^-1, with a mass transfer zone of 5.89 cm. The importance of alginate for the adsorbent development has been successfully proven.