Low-cost sorbent for the removal of aniline and methyl orange from liquid-phase: Aloe Vera leaves wastes

Alginate magnetic graphene oxide biocomposite synthesis for removal of aromatic amines from aqueous samples

In the present work, alginate magnetic graphene oxide biocomposite was synthesized for the removal and extraction of aromatic amines (aniline, p-chloroaniline (PCA), and p-nitroaniline (PNA)) from water samples. The biocomposite was investigated for its physiochemical characteristics such as surface morphology, functional groups, phase determination, and elemental composition. The results revealed that the functional groups of graphene oxide and alginate retained in biocomposite with magnetic properties. The biocomposite was applied to water samples for the removal and extraction of aniline, p-chloroaniline, and p-nitroaniline through adsorption process. The adsorption process was studied under various experimental conditions like time, pH, concentration, dose, and temperature, and all the parameters were optimized. The maximum adsorption capacities at room temperature have an optimum pH = 4 for aniline = 18.39 mg g^-1, for PCA = 17.13 mg g^-1, and for PNA = 15.24 mg g^-1. Kinetic and isotherm models showed that the experimental data is best fitted to pseudo-second-order kinetic model and the Langmuir isotherm model. Thermodynamic study suggested that the adsorption process is exothermic and spontaneous. Ethanol was found to be the best eluent for the extraction of all the three analytes suggested by the extraction study. The maximum percent recoveries from spiked water samples were calculated for aniline = 98.82%, PCA = 96.65%, and PNA = 93.55% which showed that alginate magnetic graphene oxide biocomposite could be a useful and ecofriendly adsorbent for the removal of organic pollutants in water treatment processes.

WITHDRAWN: Heavy metal ions and dyes removal from aqueous solution using Aloevera-based biosorbent: A systematic review

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Ionic liquid treated leaves of Juglans regia as an adsorbent for the removal of methyl orange dye: experimental, computational, and statistical approach

The novel biosorbents prepared by surface modification from leaves of Juglans regia plant were exploited for removal of methyl orange dye from aqueous solution. The leaves in the form of dust and charcoal were separately impregnated with 1-butyl-3-methyl imidazolium bromide (I) to obtain adsorbents namely J. regia dust/charcoal impregnated with I (JRDI/JRCI) which were characterized using advanced analytical approaches. The impregnation of ionic liquid was confirmed by the appearance of new bands. Langmuir isotherm fitted well; the calculated adsorption capacity being 59.37 (JRDI) and 102.72 mg g^-1 (JRCI). The kinetic study revealed that sorption obeyed the pseudo-first order model; the experimental adsorption capacity being 53.53 (JRDI) and 86.82 mg g^-1 (JRCI) at selected conditions of pH 3, initial dye concentration 100 ppm, dosage of adsorbent 0.3 g and contact time 70 min. The mathematical models which predicted adsorption capacity as 51.5 (JRDI) and 82.1 mg g^-1 (JRCI) were found at par with experimental values. Fukui condensed functions revealed that adsorbents had electron deficient electrophilic reaction sites while dye had electron-rich nucleophilic reaction sites. The structural properties and good adsorption capability of adsorbents indicate that they could be used as potential, eco-friendly adsorbents for the treatment of negatively charged dye pollutants.

Recent advances in the aqueous applications of PEDOT

Water is ubiquitous in life - from making up the majority of the Earth's surface (by area) to over half of the human body (by weight). It stands to reason that materials are likely to contact water at some point during their lifetime. In the specific case of sensors however, there is a need to consider materials that display stable function while immersed in aqueous applications. This mini-review will discuss the most recent advances (2018 to 2021) in the application of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) in aqueous environments. At its heart, the use of PEDOT in aqueous applications relies on nanoscale understanding and/or nanoengineered structures and properties. This enables their use in water-based settings such as within the human body or buried in agricultural soils.

Facile Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles in the Presence of Sodium Bis (2-ethyl-hexyl) Sulfosuccinate and Their Application in Dyes Removal from Single and Binary Aqueous Solutions

A research study was conducted to establish the effect of the presence of sodium bis-2-ethyl-hexyl-sulfosuccinate (DOSS) surfactant on the size, shape, and magnetic properties of cobalt ferrite nanoparticles, and also on their ability to remove anionic dyes from synthetic aqueous solutions. The effect of the molar ratio cobalt ferrite to surfactant (1:0.1; 1:0.25 and 1:0.5) on the physicochemical properties of the prepared cobalt ferrite particles was evaluated using different characterization techniques, such as FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption analysis, and magnetic measurements. The results revealed that the surfactant has a significant impact on the textural and magnetic properties of CoFe₂O₄. The capacity of the synthesized CoFe₂O₄ samples to remove two anionic dyes, Congo Red (CR) and Methyl Orange (MO), by adsorption from aqueous solutions and the factors affecting the adsorption process, such as contact time, concentration of dyes in the initial solution, pH of the media, and the presence of a competing agent were investigated in batch experiments. Desorption experiments were performed to demonstrate the reusability of the adsorbents.

Aloe vera as Promising Material for Water Treatment: A Review

Aloe vera plant offers a sustainable solution for the removal of various pollutants from water. Due to its chemical composition, Aloe vera has been explored as coagulant/flocculant and biosorbent for water treatment. Most of the used materials displayed significant pollutants removals depending on the used preparation methods. AV-based materials have been investigated and successfully used as coagulant/flocculant for water treatment at laboratory scale. Selected AV-based materials could reduce the solids (total suspended solids (TSS), suspended solids (SS), total dissolved solids (TDS), and dissolved solids (DS)), turbidity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), heavy metals, and color, with removal percentages varied depending on the coagulant/flocculant materials and on the wastewater characteristics. In the same context, AV materials can be used as biological flocculant for wastewater sludge treatment, allowing good solid–liquid separation and promoting sludge settling. Moreover, using different methods, AV material-based biosorbents were prepared and successfully used for pollutants (heavy metal dyes and phenol) elimination from water. Related results showed significant pollutant removal efficiency associated with an interesting adsorption capacity comparable to other biosorbents derived from natural products. Interestingly, the enzymatic system of Aloe vera (carboxypeptidase, glutathione peroxidase, and superoxide dismutase) has been exploited to degrade textile dyes. The obtained results showed high promise for removal efficiencies of various kinds of pollutants. However, results varied depending on the methodology used to prepare the Aloe vera based materials. Because of its valuable properties (composition, abundance, ecofriendly and biodegradable), Aloe vera may be useful for water treatment.

Kinetics and thermodynamic studies of Methyl Orange removal by polyvinylidene fluoride-PEDOT mats

We report the preparation of poly(3,4-ethylene dioxythiophene) (PEDOT)-modified polyvinylidene fluoride electrospun fibers and their use as a novel adsorbent material for the removal of the anionic dye Methyl Orange (MO) from aqueous media. This novel adsorbent material can be used to selectively remove MO on a wide pH range (3.0-10.0), with a maximum capacity of 143.8 mg/g at pH 3.0. When used in a recirculating filtration system, the maximum absorption capacity was reached in a shorter time (20 min) than that observed for batch mode experiments (360 min). Based on the analyses of the kinetics and adsorption isotherm data, one can conclude that the predominant mechanism of interaction between the membrane and the dissolved dye molecules is electrostatic. Besides, considering the estimated values for the Gibbs energy, and entropy and enthalpy changes, it was established that the adsorption process is spontaneous and occurs in an endothermic manner. The good mechanical and environmental stability of these membranes allowed their use in at least 20 consecutive adsorption/desorption cycles, without significant loss of their characteristics. We suggest that the physical-chemical characteristics of PEDOT make these hybrid mats a promising adsorbent material for use in water remediation protocols and effluent treatment systems.

Removal of aniline from wastewater by electro-polymerization with superior energy efficiency

Removal of toxic aniline from wastewater is of great importance in industrial manufacture. Traditional electrochemical methods encounter obstacles such as high energy consumption in mineralization and severe electrode passivation in electro-polymerization. In this paper, we report a practical electro-polymerization method by using Ti/Sb-SnO₂/PbO₂ anode to treat high concentration aniline wastewater. The cyclic voltammetric experiment was conducted and the problem of electrode passivation was solved by increasing the electrode potential. In the experiments of treating aniline wastewater, the produced solid polymer can separate from water rather than sticking to electrode surface. Elemental analysis shows that oxygen is incorporated in the polymer. Experiments were conducted under different conditions, including current density, pH and initial concentration of aniline and Na₂SO₄. The electro-polymerization route accounts for nearly 50% contribution in the removal of chemical oxygen demand (COD). Our electro-polymerization method gives an apparent current efficiency (ACE) of 232.15% and an energy consumption (E_p) of 0.008658 kWh g^-1_COD^-1 when half of COD is removed at a current density of 15 mA cm^-2, pH of 7.0, initial aniline concentration of 1.2 g L^-1 and Na₂SO₄ concentration of 4 g L.^-1.

Dewaxed Honeycomb as an Economic and Sustainable Scavenger for Malachite Green from Water

Dewaxed honeycomb powder (HCP) was used as a promising adsorbent for removal of malachite green (MG) from aqueous solution. Raw honeycomb was strategically dewaxed by petroleum ether, and the purified product was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), pH_zpc, and proximate analysis. A high uptake capacity (123 mg/g) was found at neutral pH. Experimental data follow pseudo-second-order kinetics (k ₂ as 0.45 × 10^-2 g/min/mg, R ² = 0.986) and Langmuir isotherm with R ² 0.999. Thermodynamic parameters suggested a spontaneous (ΔG = -26.28 kJ/mol) and exothermic (ΔH = -11.61 kJ/mol) process, which suggests increased randomness (ΔS = 0.0486 kJ/mol) at the solid-liquid interface during the adsorption process. The material can be regenerated by ordinary salt solution (1 M NaCl) and efficiently reused for three cycles with a minimal loss in efficiency. Adsorption mechanism is proposed to be a combination of electrostatic interaction and π-π stacking between aromatic units of HCP and MG. Abundant availability, possibility of wax commercialization, economic sustainability, and comprehensive waste management make HCP an ideal choice for dye decolorization.

Bio-Waste Aloe vera Leaves as an Efficient Adsorbent for Titan Yellow from Wastewater: Structuring of a Novel Adsorbent Using Plackett-Burman Factorial Design

Titan yellow (TY), a triazene azo dye, was removed from contaminated wastewater samples using a green adsorbent recycled from Aloe vera leaves (AV) waste. Two adsorbents were developed—air-dried Aloe vera (ADAV) and thermally treated Aloe vera (TTAV). Adsorption efficacy of both adsorbents was assessed in terms of percent removal (%R) of TY and adsorption capacity (qe). ADAV had a better performance compared to TTAV. Plackett–Burman design (PBD) was exploited to establish the experimental pattern of the study. Four variables were studied: pH, adsorbent dose (AD), dye concentration (DC), and stirring time (ST). Analysis of variance (ANOVA) at 95.0 confidence interval (CI), control, and quality charts helped establish regression model(s). Characterization of both adsorbents was performed using FT-IR/Raman spectroscopy together with TGA/dTGA and SEM/energy dispersive X-ray spectroscopy (EDX) analyses. Textural properties were determined using nitrogen adsorption isotherms at 77 K. Results showed that the surface areas of ADAV and TTAV300 were 3.940 and 7.076 m2/g, respectively. Raman analysis showed that the TTAV had clear D- and G-bands. Equilibrium studies revealed that data were well fitted to Freundlich isotherm with a maximum adsorption capacity of 55.25 mg/g using Langmuir equation, and the adsorption was physisorption. Adsorption followed a pseudo-second order that occurred in two steps—diffusion and then adsorption.

Environmentally Friendly Mesoporous Nanocomposite Prepared from Al-Dross Waste with Remarkable Adsorption Ability for Toxic Anionic Dye

In this work, a mesoporous nanocomposite composed of nanogibbsite (α-Al(OH)3) and nanosilica was prepared. Gibbsite nanoparticles (GNPs) with a crystal size of ≈38 nm were prepared from Al-dross industrial waste products in an acidic environment at 100°C. Nanosilica (NS) with a crystal size of ≈13 nm was prepared from sodium silicate using dilute hydrochloric acid. The deposition of nanosilica onto gibbsite particles was investigated. The mesoporous silica-gibbsite (NSG) nanocomposite was examined by evaluating its ability to adsorb the toxic anionic dye Eriochrome black T (EBT) from aqueous solution. The compositional and morphological properties of NSG nanocomposites were studied by means of the FTIR spectroscopy, X-ray fluorescence (XRF), XRD, SEM, and TEM techniques. The effect of dye concentration, pH, adsorbent dose, contact time, and temperature was investigated. The sorption models, the isotherms, and the thermodynamic parameters ΔHo, ΔGo, and ΔSo were evaluated. The N2 adsorption-desorption isotherms revealed that mixing the two prepared materials (NS and GNPs) to form the NSG nanocomposite resulted in good properties (a surface area of 62.34 m2·g−1, a pore radius of 22.717 nm, and a pore volume of 0.7081 cm3·g−1). The results show that the prepared NSG nanocomposite has a remarkable ability to adsorb toxic anionic dyes.

Photocatalytic Degradation of Diazinon in Aqueous Solutions Using Immobilized MgO Nanoparticles on Concrete

Photocatalytic degradation of diazinon in the aqueous solution using UV light and MgO nanoparticle (NPs) immobilized on the concrete was investigated. Prepared catalyst was characterized using TEM, XRD, SEM, and EDX techniques. The results showed that the average particle size of immobilized MgO NPs was 38.3 nm and NPs appropriately was coated on the concrete surface. The performance of degradation and mineralization of diazinon was evaluated by HPLC and TOC techniques, respectively. The effect of operational parameters including pH value, initial pesticide concentration, and contact time were studied on the removal and mineralization of diazinon by a photocatalytic process. The results showed that the MgO NPs and UV light had little effect in removing pesticide when used individually. On the other hand, diazinon can be effectively degraded by immobilized MgO NPs in the presence of UV light. Degradation products of diazinon using the proposed photocatalytic technique were identified by the GC-MS analysis. The maximum diazinon removal (99.46 %) was obtained under the conditions; pH 7, diazinon concentration of 5 mg/L, and contact time of 120 minutes. Also, the lowest energy consumption conditions were as follow; pH 7, diazinon concentration of 5 mg/L, and contact time of 30 minutes.

Aloe vera waste biomass-based adsorbents for the removal of aquatic pollutants: A review

Aloe vera has been cultivated for many centuries for its beneficial properties, finding application in a wide range of medical and health products. Nowadays, the research has also focused on an alternative use of Aloe vera which is related to environmental applications such as clean water technology/wastewater treatment process. In recent years, biosorption has been shown to be a cost-effective and efficient alternative method for removing various pollutants from wastewater and water. This work provides a comprehensive review on using Aloe vera waste biomass-based sorbents, as well as modified counterparts, for the removal of heavy metals, dyes and other pollutants from aqueous media. The discussed biosorbents have been grouped in five categories based on the treatment of the Aloe vera leaves. Adsorption mechanisms, in addition to the significant factors influencing sorption capability like physical and chemical properties of the adsorbent, initial concentration, initial pH and temperature of the solution, dosage and contact time, have been discussed in detail. Furthermore, the applied equilibrium and kinetic models have been also summarized. The history, taxonomy, botany, and applications of Aloe vera are also presented in brief.

Assessing the Aflatoxin B₁ Adsorption Capacity between Biosorbents Using an In Vitro Multicompartmental Model Simulating the Dynamic Conditions in the Gastrointestinal Tract of Poultry

Experiments were carried out to evaluate the effectiveness of three different biosorbents (banana peel, Pyracantha leaves, and Aloe powder) in removing aflatoxin B₁ (AFB₁). A noncommercial mycotoxin binder (zeolite) was used as a reference material. A laboratory model that simulated the in vivo conditions of the poultry gastrointestinal tract was utilized to prove the removal efficiency of the biosorbents when added to AFB₁-contaminated diet (100 µg/kg). The concentration of AFB₁ was determined using antibody-based immunoaffinity column and spectrofluorometry methodologies. Z potential (ζ), point of zero charge (pHpzc), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), and UV-Vis diffuse reflectance spectroscopy (DRS) techniques were used to further characterize the biosorbents. The addition of the biosorbents (1.5%, w/w) to the diet significantly reduced the bioavailability of AFB₁ in the intestinal section. The highest aflatoxin adsorption values were 69% and 70% using Aloe powder and zeolite, respectively. A moderate biosorption uptake of 46% was achieved using Pyracantha leaves. The biomaterial with the lowest removal capacity was banana peel (28%). In conclusion, Aloe powder could be used as an alternative to conventional systems for AFB₁ removal.

Cationic Surfactant-modified Clay as an Adsorbent for the Removal of Synthetic Dyes from Aqueous Solutions

In this study, the potential of hexadecyl trimethyl ammonium bromide modified montmorillonite (HDTMA-Mt) to remove the synthetic dyes Alizarin Red S (ARS) and Bromocresol Green (BCG) from aqueous media was assessed. The effect of different factors including surfactant loading rate onto the clay, contact time, pH, adsorbent dosage and dye concentrations, on the removal of ARS and BCG in batch systems were investigated. The adsorbent was characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). The equilibrium time for ARS and BCG was reached at 40 and 20 min, respectively, under optimized conditions (i.e. pH = 3, adsorbent dosage=1 g/L, surfactant loading rate onto the clay 70% of the cation exchange capacity (CEC) for ARS and 120% of the CEC for BCG, ARS concentration 50 mg/L and BCG concentration 500 mg/L). The adsorption rate of both dyes fitted the pseudo-second-order kinetic model and the equilibrium data was described by the Freundlich isotherm equation. The maximum monolayer adsorption capacities were equal to 666.6 and 1250 mg/g for ARS and BCG, respectively. Therefore, the HDTMA-Mt can be considered as an effective adsorbent for the removal of ARS and BCG from aqueous solutions.

Adsorption of Congo Red Dye from Aqueous Solutions by Montmorillonite as a Low-cost Adsorbent

In this study, the sorption of Congo red (CR), as a toxic dye, from aqueous media was investigated using montmorillonite (MMT) as a low-cost adsorbent. The influence of several factors such as contact time, pH, adsorbent dosage, dye content, and ionic strength was investigated on the dye removal. MMT was characterized by Fourier transformed infrared (FTIR) spectroscopy and X-ray diffractometer (XRD). Different kinetic and isotherm models including pseudo-first and pseudo-second order kinetic and Langmuir and Freundlich were applied to analyze experimental data, respectively. The results showed that the data were well fitted by pseudo-second-order kinetic and Freundlich isotherm models. The optimum conditions for the sorption of CR were achieved over 40 min and at pH=2. According to the results of the present study, MMT can be used as a low-cost, eco-friendly and effective option for the adsorption of CR from aqueous solutions.