Congo Red Removal Efficiency Research Articles

Carboxylic acid-assisted hydration for the preparation of mesoporous magnesium hydroxide/magnesium oxide with ultra-high adsorption performance and selective adsorption: Experiments and DFT investigations

Herein, mesoporous Mg(OH)2 is prepared by one-step hydration method using microcrystalline magnesite as raw material and acetic acid as hydration agent, and the mesoporous MgO is obtained after thermal conversion. The adsorption experiments on three single dye systems (Congo red (CR), methyl orange (MO) and methylene blue (MB)) and three binary mixed dye systems (CR/MO, CR/MB and MO/MB) show that mesoporous MgO possesses superior adsorption selectivity towards anionic dyes. The mesoporous Mg(OH)2 with cardroom-like structure, obvious pore channel and abundant edge and concern shows good adsorption capacity for CR (6591.96 mg/g) and MO (3087.04 mg/g). The mesoporous MgO obtained by calcination has high specific surface area (66 m2/g) and partially inherits the cardroom-like structure of Mg(OH)2, exhibiting remarkable adsorption performance (CR: 10521.89 mg/g; MO: 6694.65 mg/g). CR and MO adsorption on the Mg(OH)2/MgO accords with the Langmuir model and pseudo-second-order kinetic model. The density functional theory (DFT) is employed to evaluate the reactivity of CR/MO, such as molecular frontier orbital energies and energy gap, demonstrating that CR exhibits superior reactivity and adsorptive capacity in comparison to MO. The MgO sample is regenerated by calcination after CR/MO adsorption and the CR removal efficiency of MgO reaches above 85 % after 10 cycles.

Preparation of GO/BiOI composites and their degradation performance in Congo red solution

GO/BiOI photocatalytic nanocomposites were synthesized through a hydrolysis precipitation method, utilizing (Bi(NO3)3·5H2O) as the bismuth precursor and graphene oxide (GO) as the substrate. The removal effect of the material on Congo red (CR) in water was investigated by taking CR as the target pollutant. The composite’s structure and characteristics were examined through various analytical methods, including XRD, BET, FT-IR, FE-SEM, TEM, and UV–Vis techniques. The findings indicate that the integration of GO with BiOI preserves the layered crystalline structure of BiOI and mitigates particle aggregation. The specific surface area of the GO/BiOI composites increased significantly, from 21.98 m2/g for BiOI to 80.2586 m2/g, and the bandgap was decreased from 1.94 eV to 1.82 eV. The GO/BiOI photocatalytic degradation conformed to the first-order kinetic model. When the initial concentration of CR was 20 mg/L, the rate constant was the largest, and the correlation coefficient was 0.9988. At a dosage of 200 mg/L for GO/BiOI, with an initial concentration of 20 mg/L for CR solution, a pH level of 5, and under LED illumination at 12 W, the composite material achieved a CR removal efficiency of 96.09 %. After being reused five times, the removal rate could still reach more than 90 %.

Congo red removal using microwave assisted pyrolysis derived magnetic hemp hurd biochar

Industrial hemp hurd (HH) are the residue obtained after the decortication of the hemp plant for fibre production, which is seldom explored for biochar potential and as adsorbent for dye removal. The present study focused on the microwave-assisted pyrolysis (MAP) of HH for biochar production, magnetization and application for Congo red (CR) removal from aqueous solutions. Magnetic hemp hurd biochar (MHB) depicted a heterogeneous surface with 4.84 µm pore size, 17.64 m2/g surface area, and 10.05 wt% Fe. CR removal of 92 % was achieved under optimum conditions i.e., treatment time: 120 min, pH: 8, and initial CR concentration: 10 mg/L with MHB dosage of 0.6 g/L. The CR adsorption on MHB was well-fitted with the Freundlich isotherm (R2 - 0.971), owing to the heterogeneous surface of MHB. A strong match with pseudo-second order model (R2 - 0.973), indicated chemisorption as the likely adsorption mechanism. MHB exhibited 87 % CR removal efficiency after three successive reutilization cycles. The outcomes of CR removal efficiency and MHB reusability indicated its potential application for adsorptive removal of CR from aqueous systems.

Fabrication and characterization of C–doped TiO2 nanoparticles for the photodegradation of organic dyes

A low-cost sol-gel method is used to synthesize C-doped TiO2 (C–TiO2) nanoparticles. Nanoparticles of undoped TiO2 and varying C weight percentages (4%, 6%, and 8%) of C–TiO2 are generated. XRD, FTIR, FESEM-EDS, UV–Vis DRS, PL, BET, and XPS are used to analyze the characteristics of all the nanoparticles. The EDS data indicate that the TiO2 lattice has been successfully doped with carbon. The band-gap energy of 6% C–TiO2 is shifted to 2.94 eV, as confirmed by UV–Vis DRS, resulting in improved visible-light absorption and, hence, increased photocatalytic activity by lowering the electron-hole recombination rate. Under natural sunlight irradiation, 6% C–TiO2 achieves a 91% removal efficiency of Rhodamine B (RhB) dye in 90 min and 84% removal efficiency of Congo Red (CR) dye in 30 min. A probable photodegradation pathway was estimated using the scavenger test, and the •O2 − and •OH radicals are recognized as potentially active species for RhB degradation.

Room temperature synthesis of copper-modified ZIF-8/Chitosan for enhanced adsorptive removal of congo red

The synthesis of Cu(II)-doped ZIF-8/Chitosan by means of the one-pot method at room temperature was successfully carried out. The synthesized materials exhibit enhanced adsorption properties for the removal of Congo red (CR) dye. The structural and morphological properties of Cu(II)-doped ZIF-8/Chitosan were characterized. Cu(II)-doped ZIF-8/Chitosan achieved the most optimal CR removal efficiency and CR adsorption capacity (153.85 mg/g) due to its higher specific surface area (522.776 m2/g) compared to ZIF-8/Chitosan (514.882 m2/g). Electrostatic attraction, hydrogen bonding, and π-π interaction are the main interactions for the higher adsorption performance. The CR adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. The results of the thermodynamic adsorption indicated that the process of CR adsorption by Cu-doped ZIF-8/Chitosan was an endothermic reaction. The experimental results indicate that the Cu(II)-doped ZIF-8/Chitosan material has the potential to be used in wastewater treatment for the removal of anionic dyes.

Efficient degradation of organic pollutants with sodium percarbonate by activation with CuFeS2 prepared from precursors of different valence states

Four chalcopyrite (CuFeS2) catalysts were fabricated by a hydrothermal method using different copper and iron precursors at different valence states. The prepared CuFeS2 samples were then evaluated for the oxidative degradation of Congo red (CR) using sodium percarbonate (SPC) as the oxidant. The sample of CuFeS2-1, which was prepared from Cu (I) and Fe (II) precursors, exhibited the highest CR removal efficiency of 96.6% among the four CuFeS2 samples. Using CuFeS2-1 as the optimum catalyst, the effects of operation and environmental factors on the removal efficiency of CR were investigated in detail. Mechanism studies showed that CO3•− was the main reactive oxidative species in the reaction process, while O2•− and low-valent sulfur species together promoted the regeneration of Fe (II) and Cu (I) sites on the catalyst. Furthermore, density functional theory (DFT) calculations were used in combination with liquid chromatography-mass spectrometer (LC-MS) to propose the plausible degradation pathway. Finally, toxicity prediction showed that most of the degradation products showed decreased toxicity compared to the parent CR, and toxicity evaluation with Vigna radiata further revealed the declined toxicity.

ZIF-8 metal-organic network/poly(vinyl alcohol) composite for adsorptive removal of various organic dyes

The removal of organic dyes from wastewater is crucial for environmental protection and water treatment. In this study, a ZIF-8/poly(vinyl alcohol) (PVA) composite was prepared for highly efficient dye adsorption using the contra-diffusion method. We investigated the conditions for ZIF-8-PVA to adsorb congo red (CR), including the influences of contact times, initial CR concentrations, pH values, and cyclic use. The results demonstrated that ZIF-8-PVA had a high Brunauer-Emmett-Teller (BET) surface area of 1704.03 m2/g. It exhibited a high removal efficiency of 98.43 % for CR, and its maximum adsorption capacity was 829.39 mg/g. After six cycles of adsorption, the removal efficiency of CR remained over 94.36 %. The removal efficiency of CR under a range of pH from 3 to 10 was consistently over 96.30 %. Moreover, ZIF-8-PVA also displayed adsorption capacity for various cationic and anionic dyes. The adsorption process aligned well with both the Langmuir model and the pseudo-second-order kinetic model. Based on FTIR, XPS, and swelling degree analyses, the adsorption mechanism was elucidated. Due to its universality and reusability, ZIF-8-PVA is suitable for practical application.

Upcycling of sugar refining mud solid waste as a novel adsorbent for removing methylene blue and Congo red from wastewater.

The feasibility of utilizing the mud solid waste (MSW) produced during the carbonation process of sugar refining as a cost-effective and environmentally friendly alternative for the water removal of methylene blue (MB) and Congo red (CR), being highly utilized organic dyes representing cationic and anionic species, respectively is presented. Prior to its use, the MSW was dried at 110 °C for 24 h and sieved through a 100-mesh screen. The chief constituent of the MSW utilized was CaCO3, with a point of zero charge (PZC) found at pH 8.4 and 7.96 m2 g-1 total surface area. XRD and FTIR data indicate the presence of interactions between the dyes and the MSW surface, indicating effective adsorption. Different variables, such as initial dye concentration, MSW weight, solution pH, contact time, and temperature, were all examined to determine the optimal dye removal conditions. A central composite design (CCD) approach based on response surface methodology (RSM) modeling was utilized to identify statistically significant parameters for MB and CR adsorption capacities onto the MSW adsorbent. The removal equilibrium was typically reached in 120 minutes, with the greatest removal efficiency of CR taking place at pH 2 and 328 K, while the highest MB removal efficiency was obtained at pH 12 and 296 K. Kinetic studies suggest the adsorption of both dyes on the MSW follow pseudo-second-order rates, as evident through the high correlations obtained. Linearized and non-linearized Langmuir models showed strong correlations indicating maximum adsorption capacities of 86.6 and 72.3 mg g-1 for MB and CR, respectively. High regeneration and reusability potential of the MSW was demonstrated especially for the adsorption of CR, where the removal efficiency was nearly constant throughout five adsorption cycles, ranging from 93 to 91%, while the reduction in the removal for MB was much more significantly impacted, diminishing from 95 to 79% after the five cycles.

NaOH-Activated Natural Glauconite for Low-Cost Adsorption of Congo Red Dye

To explore the adsorption of Congo red (CR) dye from textile effluent, natural clay glauconite was employed as a sustainable and inexpensive adsorbent. The effects of varying concentrations of sodium hydroxide (NaOH) on glauconite alteration were examined. Furthermore, this research focuses on the optimal NaOH concentration that improves removal efficiency and adsorption capacity. Thus, four NaOH solutions of concentrations ranging from 1 M to 4 M were used to activate glauconite raw (GL), indicated as GLACT1M, GLACT2M, GLACT3M, and GLACT4M. These samples were characterized using different analysis tools. The effects of starting concentration, adsorption time, adsorbent dosage, pH, temperature, and reusability on removal efficacy were all investigated. The data show that the CR removal efficiency increases with modification up to a 2 M NaOH activation, beyond which it begins to decrease. At 25 °C and pH 7, the CR removal efficiencies were ~77%, 72%, 80%, 34.5%, and 30.5% by GL, GLACT1M, GLACT2M, GLACT3M, and GLACT4M, respectively. Batch experiments were performed to explore both the kinetics and isotherms of CR adsorption to determine the impact of different experimental conditions accurately. Moreover, isotherm interpretations demonstrated that the Freundlich isotherm closely matches the experimental results. The pseudo-second-order model clearly explains the obtained results (R2 = 0.998) from 5 to 25 ppm for GL, GLACT1M, GLACT2M, and GLACT3M, but GLACT4 is expressed by the Elovich model from 20 to 25 ppm. The reusability investigation revealed that the reusability of adsorbents could be achieved efficiently. The findings suggest that glauconite and its NaOH-activated forms can be employed as natural and affordable adsorbents for removing CR from textile effluent.

Construction of a reusable Ce-Fe bimetallic oxide flocculant featuring coordinately unsaturated Fe3+ Lewis acid sites for highly efficient and selective removal of Congo Red

Numerous flocculants have been developed to target the removal of Congo Red (CR), a non-degradable and carcinogenic dye. However, challenges such as non-reusability and potential adverse effects limit their widespread application. To address this, a novel cerium oxide-iron (III) oxide (CeO2-Fe2O3, denoted as CeFe) flocculant featuring coordinatively unsaturated Fe3+ Lewis acid sites was synthesized for selective CR removal. Unlike many counterparts, CeFe maintains its efficiency over repeated uses and showcases exceptional stability. The pronounced interaction between CeO2 and Fe2O3 enhances the coordination unsaturation in CeFe, amplifying the electrophilicity of Fe3+ species and creating more Lewis acid sites. According to the results of characterizations and DFT studies, these sites effectively chelate the −NH3 and −N = N − groups on CR molecules, leading to efficient flocculation. Under optimized conditions (pH=6, initial CR concentration of 400 mg/L, and CeFe dosage of 50 mg/L), CeFe achieved a CR removal efficiency of 95.60 ± 0.90%. This research positions CeFe as a promising, reusable flocculant for efficient CR removal, suggesting a new direction in flocculant design.

Efficient adsorption of azo anionic dye Congo Red by micro-nano metal-organic framework MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge: Preparation, characterization and adsorption performance

Micro-nano metal-organic framework (MIL-68(Fe)) for efficient adsorption of azo anionic dye Congo red (CR) was successfully prepared by one-step hydrothermal method under acidic environment. And a MIL-68(Fe)/chitosan composite sponge (MIL-68(Fe)/CS) was prepared under the coating of chitosan (CS). After comparing the performance of MIL-68(Fe) and MIL-68(Fe)/CS, we focus on exploring MIL-68(Fe)/CS. It ensured the CR removal efficiency while reaching the adsorption equilibrium faster than MIL-68(Fe), and solved the defect that the powder was difficult to be stripped by water after adsorption. The physicochemical properties and surface morphology of the adsorbent were characterized by SEM, FTIR, XRD, TGA, BET, and Zeta potential. The effects of pH, contact time, adsorbent dosage, initial solution concentration and temperature on the adsorption performance of the adsorbent were systematically analyzed. The pseudo-second-order model and the Sips model were most consistent for the adsorption process, indicating that the adsorption process of MIL-68(Fe)/chitosan composite sponge on CR is a complex physicochemical process. The removal rates of CR by MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge reached the maximum values of 99.55 % and 99.51 % at 318 K, respectively. And the maximum adsorption capacity of CR by MIL-68(Fe)/chitosan composite sponge at 318 K was 1184.16 mg·g−1. After six cycles of adsorption and desorption, the removal rate of CR was still higher than 80 %. The synergistic effects of π-π stacking, electrostatic interactions, hydrogen bonding and pore filling have important effects on CR removal.

Enhanced adsorption effect of defect ordering Mg/Al on layered double hydroxides nanosheets with highly efficient removal of Congo red

The non-conventional structure layered double hydroxides (LDHs) as pollutant adsorbents with significant adsorption efficiency are promising valuable research topics. In this work, the defect ordering MgAl-LDHs nanosheets for the highly efficient removal of Congo red (CR) are designed and fabricated by a facile environmental-friendly hydrothermal method based on solid insoluble substances magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) as precursors. The decrease of Mg/Al ordering changes the interlayer spacing of LDHs and improves the defect sites with low oxygen coordination on the LDHs laminate, which enhances the removal efficiency of CR from 45.6 to 97.7%. This study reveals that a defect enhancing combined mechanism of surface adsorption and the anion-exchange in MgAl-LDHs can obtain an outstanding adsorption efficiency for removing CR. The reactivity of the Mg/Al disorder with O defect on the LDHs laminate increases with the reduction of frontier orbitals energy gap (ΔEgap), resulting in a high adsorption capacity for CR. The uncover of the defect enhancing adsorption mechanism provides a new strategy to fabricate MgAl-LDHs with high capability for wastewater remediation.

A strategy-purifying wastewater with waste materials: Zn2+ modified waste red mud as recoverable adsorbents with an enhanced removal capacity of congo red

The strategy, called purifying wastewater with waste materials (PWWM), can simultaneously improve the secondary utilization of industrial waste materials and in turn, reduce environmental pollution. However, the PWWM strategy has still not been extensively used because of its low purification efficiency of organic pollutants and extremely difficult secondary utilization process. Herein, we use zinc aluminum silicate (ZAS) to modify waste granular red mud (GRM) to form a recoverable adsorbent, called ZAS/GRM adsorbent. The ZAS has been found to exhibit exceptional adsorption performance with the ability to firmly anchor onto the surface of GRM, in which heavy metal ions can effectively solidify and reduce their outflow. Furthermore, many voids have been tactfully designed in the ZAS/GRM adsorbents by using a water vapor project, which provide more active sites for congo red (CR) organic dye, thereby remarkably improving the removal efficiency of CR. From our purification of CR, we find that the CR adsorption capacity of the ZAS/GRM adsorbent is 3.509 mg g−1, which is four times higher than pure GRM (0.820 mg g−1). This study demonstrates our PWWM strategy is highly effective and can inspire more research on waste reuse.

Fabrication of a corn stalk derived cellulose-based bio-adsorbent to remove Congo red from wastewater: Investigation on its ultra-high adsorption performance and mechanism

A cellulose-based bio-absorbent with various and plenty of amino groups was successfully prepared from corn stalk to achieve quantitative removal of Congo red from wastewater with wide pH values (5 ≤ pH ≤ 10). The maximum removal amount was 8.0 mmol·g−1 (5572 mg·g−1) under pH = 6.0 and 45 °C, which was obviously higher than reported absorbents. Investigation on dynamic adsorption and recyclability in authentic wastewater found that the removal efficiency of Congo red was >98 % within 180 min and decreased slightly in industrial water after five cycles, denoting this adsorbent with great potential for environmental application. The characterization results proved that 7.58 mmol·g−1 of different amino groups (-NH2, -NH- and -NR2) were introduced on adsorbent surface by two steps of modification and were the major functional groups for adsorption of Congo red. The inferred adsorption mechanism revealed that Congo red could be adsorbed equivalently on the amino groups by strong electrostatic interactions or hydrogen bonds. Different amino groups played different roles in adsorption due to great differences in protonation ability in 5 ≤ pH ≤ 10. The study was expected to high-efficiently remove Congo red from acidic or alkaline wastewater, and offered an alternative strategy for biowaste treatment of corn stalks in a high value-added manner.

A novel route for the facile synthesis of NH2-MIL-53(Fe) and its highly efficient and selective adsorption of congo red

Metal-organic frameworks (MOFs) have shown attractive advantages in adsorbing dyes from wastewater. However, their complex synthesis processes and poor stability have limited their applications. Herein, we proposed a novel two-step route to prepare NH2-MIL-53(Fe) at room temperature and investigated its dye adsorption performance. The prepared NH2-MIL-53(Fe) displayed high water stability in the pH range of 3–11. Moreover, NH2-MIL-53(Fe) showed a significantly higher adsorption capacity and faster adsorption rate towards congo red (CR) than the other selected dyes, with more than 99 % of CR being removed by NH2-MIL-53(Fe) within 20 min. The maximum adsorption capacity of NH2-MIL-53(Fe) for CR was 1877 mg·g−1. Besides, the removal efficiency of CR could maintain higher than 80 % within the tested pH range (3 to 11), and removal efficiency was consistently higher than 95 % at different NaCl concentrations (0 to 0.4 M). The dynamic CR adsorption process matched the pseudo-second-order kinetic model and fitted well using the Langmuir model, suggesting that the adsorption of CR onto NH2-MIL-53(Fe) was a monomolecular-layer chemical adsorption process. More importantly, NH2-MIL-53(Fe) showed high removal efficiency and good reusability towards CR in both synthetic and model wastewater. Mechanistic studies suggested that the removal of CR was attributed to the synergistic effects of the π-π stacking interactions, hydrogen bonds and electrostatic interactions between CR and NH2-MIL-53(Fe). Overall, the present study provides a novel strategy for the facile synthesis of NH2-MIL-53(Fe), highlights the excellent adsorption performance and reusability towards CR and underlies the adsorption mechanisms involved.

Characterization of microspheres γ-AlOOH and the excellent removal efficiency of Congo red

In this paper, Microspheres γ-AlOOH (MB) was synthesized by spray drying. Compared with commercial boehmite (CB) adsorbent, the microsphere morphology of MB is stronger than that of bulk CB in terms of thermal stability and specific surface area. The adsorption equilibrium of MB on Congo red under acidic conditions was reached within 20 min, much faster than CB. The adsorption process of MB on Congo red conformed to the pseudo-second-order and Langmuir model. The maximum adsorption capacity reached 1131.94 mg g−1, which was better than that reported in the literature. The activation energy of 21.11 kJ mol−1 and Gibbs free energy of the adsorption process of Congo red by MB were analyzed, etc. The adsorption process was determined as physical adsorption. MB has strong regeneration and adsorption capacity and has great potential for adsorbing Congo red in wastewater.

Synthesis of Sulfonated Polystyrene-Based Porous Activated Carbon for Organic Dyes Removal from Aqueous Solutions

Nowadays, aquatic pollution is one of the most important global challenges, due to discharges a wide variety of various hazardous materials from different activities which have significant environmental, economic and healthy impacts. Industries and activities related to organic dyes onsume large amounts of water and contribute significantly to the growing problem of water pollution. The current study describes the conversion of plant wastes into activated carbon sphere incorporated sulfonated polystyrene (AC/SPS) for adsorptive removal of Rhodamine B (RhB) and Congo Red (CR) dyes in a batch process. The prepared materials were characterized by different techniques such as XRD, FTIR, FESEM, TEM, BET-BJH, and TGA. The AC/SPS in weight ratio of 10% was used as a novel adsorbent for RhB and CR remediation. Batch adsorption experiment have been studied by investigating the effect of contact time, adsorbent dose, initial pH, and temperature. The maximum removal efficiency of RhB and CR onto AC/SPS under optimized conditions was estimated to be 34% and 98%, respectively. In addition, it has been found that Freundlich model provided the most appropriate fit for the adsorption of both RhB and CR dyes. Based on the thermodynamic study, it was proven that the adsorption process for both dyes is endothermic and spontaneous. The change in entropy was estimated to be 190.59 and 65.40 J/mol K for CR and RhB dyes, respectively. The kinetic study revealed that the adsorption of CR and RhB dyes followed the pseudo-second order and pseudo-first order kinetic models, respectively.Graphical Abstract

Removal of refractory dyes by a novel chlorine-free coagulant of polyferric-silicate-acetate (PFSA): Characterization and performance evaluation

A novel chlorine-free coagulant of polyferric-silicate-acetate (PFSA) with varying Si/Fe molar ratios was applied to treat Congo red (CR) dye wastewater in order to determine its coagulation ability and performance. Images obtained from Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis revealed the functional group and morphology of PFSA. The results showed that the CR removal efficiency was the best at the Si/Fe molar ratio 1:1. According to the analysis of FTIR and SEM, PFSA was a polymeric complex containing polyferric-silicate-acetate polymer and hydroxyl iron oxide, which presented closely clustered rod shaped with many particles on its surface. Compared with polyferric acetate (PFC) and polysilicic acid (PSA), PFSA was more efficient and had a broader pH range of 5.5–10. The highest CR removal efficiencies recorded for PFSA, PFC and PSA were 93.6%, 88.3% and 70.4%, respectively. In addition, PFSA and PFC had wider range of temperature at optimal conditions. The analysis of coagulation properties revealed that the mechanisms of adsorption-bridging and enmeshment coagulation acted a crucial role in the coagulation process of PFSA. Therefore, PFSA will be a promising green-coagulant for treating actual wastewater containing refractory dyes, which can reduce environmental risk.

Adsorption of endocrine disruptive congo red onto biosynthesized silver nanoparticles loaded on Hildegardia barteri activated carbon

In this research work, silver nanoparticles (AgNPs) were prepared using green procedure and loaded on Hildegardia barteri activated carbon (HBAC) and then characterized for determination of morphology, crystals structure, functional groups, surface area and porosity, and size distribution, of the composite material using Scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET), and High-resolution transmission electron microscope (HRTEM). The AgNPs/HBAC nanocomposite was used for the removal of Congo red (CR) dye from aqueous solution. The antimicrobial activity of AgNPs/HBAC was tested against Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli and Bacillus subtilis bacteria using the agar well diffusion method. Parameters such as initial CR concentration (20–100 mg/L), adsorbent dosage (0.1–1 g), contact time (0–90 min), and adsorption temperature (308, 318 and 328 K) were investigated on a batch adsorption process to estimate the CR removal efficiency. The mesoporous AgNPs/HBAC had a BET surface area of 794 m2/g which enhanced CR adsorption capacity (161.29 mg/g). The Freundlich isotherm emerged the best fitted model, indicating surface heterogeneity (multilayer adsorption) between the CR and AgNPs/HBAC surface. The CR adsorption onto AgNPs/HBAC was adequately described by a pseudo-second order kinetic model, and the overall adsorption process was governed by Webber-Morris intraparticle diffusion, and liquid film diffusion models. Thermodynamic study revealed that the adsorption ability of AgNPs/HBAC toward CR was spontaneous, feasible, and exothermic. The developed AgNPs/HBAC could be used as a nano-adsorbent to mitigate the environmental problems caused by CR in wastewater. Regeneration and reusability of AgNPs/HBAC adsorption performance indicated adsorption efficiency greater than 85 % after five successive cycles.

Evaluation of Three Biomaterials from Coconut Mesocarp for Use in Water Treatments Polluted with an Anionic Dye

Coconut consumption leads to the generation of a large number of fibrous residues such as epicarp and mesocarp. In this study, bioadsorbents were prepared from coconut shells (CS), coconut cellulose (CC) and treated coconut cellulose (MCC) with cetyl trimethyl ammonium chloride (CTAC) for the elimination of Congo red (CR) in a watery solution. The impact of the adsorbent quantity (15, 25 and 35 mg) and initial concentration (40, 70 and 100 mg/L) were evaluated. Fourier transform infrared spectra (FTIR) confirmed the existence of OH−, C=O, COOH and CH2 groups in the adsorbents as well as the deformation of the bands between 3400 and 3800 cm−1 after the adsorption of CR, which was attributed to its capture in the bioadsorbent. From the bromatological analysis, a content of 48.94% lignin, 35.99% cellulose and 10.51% hemicellulose was found. SEM images showed a lignocellulosic essential surface origin for all adsorbents with presence of folds, roughness of an irregular exposed area and fibrous filaments. The average particle size was 0.45 mm and adsorbents had a mean porosity of 0.58. Increasing the initial concentration had a beneficial influence on the removal efficiency of CR, achieving a 99.9% removal with MCC. CS showed slow kinetics in the initial stages whereas CC and MCC achieved 78% and 99.98% removal at 120 min, respectively; an equilibrium was reached at 480 and 20 min, respectively. MCC, CC and CS achieved a maximum qe of 256.12 mg/g, 121.62 mg/g and 17.76 mg/g, respectively.