Fabrication of different adsorbents based on zirconium oxide, graphene oxide, and dextrin for removal of green malachite dye from aqueous solutions

Development of inorganic and mixed matrix membranes for application in toxic dyes-contaminated industrial effluents with in-situ treatments

Dyes are the most ubiquitous organic pollutants in industrial effluents. They are highly toxic to both plants and animals; thus, their removal is paramount to the sustainability of ecosystem. However, they have shown resistance to photolysis and various biological, physical, and chemical wastewater remediation processes. Membrane removal technology has been vital for the filtration/separation of the dyes. In comparison to polymeric membranes, inorganic and mixed matrix (MM) membranes have shown potentials to the removal of dyes. The inorganic and MM membranes are particularly effective due to their high porosity, enhanced stability, improved permeability, higher enhanced selectivity and good stability and resistance to harsh chemical and thermal conditions. They have shown prospects in filtration/separation, adsorption, and catalytic degradation of the dyes. This review highlighted the advantages of the inorganic and MM membranes for the various removal techniques for the treatments of the dyes. Methods for the membranes production have been reviewed. Their application for the filtration/separation and adsorption have been critically analyzed. Their application as support for advanced oxidation processes such as persulfate, photo-Fenton and photocatalytic degradations have been highlighted. The mechanisms underscoring the efficiency of the processes have been cited. Lastly, comments were given on the prospects and challenges of both inorganic and MM membranes towards removal of the dyes from industrial effluents.

Synthesis & fabrication of O-linked polymeric hybrids for recovery of textile dyes: Closed loop economy

Dyes are an important resource employed for the production systems in textile, paper, paint and leather industry. An estimate of 200,000 tons of dyes are discharged as textile effluent each year worldwide. It becomes imperative to recover these dyes by treating the effluents using economically viable routes. The present research was undertaken with the objective to attain zero emission and zero waste through development of novel polymeric hybrids as adsorbents. For this purpose, metal moieties (Al3+, Si4+, Ti4+ and Zr4+) were hybridized with polyacrylic acid, and cellulose acetate for the uptake of selected dyes under optimized parameters. The structural elucidation of four synthesized hybrids (MP-Al, MP-Si, MP-Ti and MP-Zr) by FTIR, EDX and TGA confirmed O-linked grafting of metal moieties with polymers and thermally stable porous materials. SEM micrographic images displayed void spaces providing channels for effective adsorption. The batch experiments demonstrated removal of malachite green (77-96%) and congo red (70-82%) upon contact of initial 45 min on polymeric hybrids On the other hand, pristine polyacrylic acid and cellulose acetate showed remarkably low removal of dyes. The adsorption mechanism is proposed as physical in nature following type II isotherm. Further, Langmuir and Ho's pseudo second order fitness was evaluated. In order to determine the economic viability of the present research, the real textile dyes were recovered in three consecutive cycles of adsorption and chemical treatment of hybrids. The results propose a system with positive impact on economy by maximum utilization of hybrids as adsorbents and recovery of textile dyes for reuse in textile processing.

Selective adsorption of organic dyes from aqueous environment using fermented maize extract-enhanced graphene oxide-durian shell derived activated carbon composite

A secure aquatic environment is essential for both aquatic and terrestrial life. However, rising populations and the industrial revolution have had a significant impact on the quality of the water environment. Despite the implementation of strong and adapted environmental policies for water treatment worldwide, the issue of organic dyes in wastewater remains challenging. Thus, this study aimed to develop an efficient, cost-effective, and sustainable material to treat methylene blue (MB) in an aqueous environment. In this research, maize extract solution (MES) was utilized as a green cross-linker to induce precipitation, conjugation, and enhance the adsorption performance of graphene oxide (GO) cross-linked with durian shell activated carbon (DSAC), resulting in the formation of a GO@DSAC composite. The composite was investigated for its adsorptive performance toward MB in aqueous media. The physicochemical characterization demonstrated that the cross-linking method significantly influenced the porous structure and surface chemistry of GO@DSAC. BET analysis revealed that the GO@DSAC exhibited dominant mesopores with a surface area of 803.67 m2/g. EDX and XPS measurements confirmed the successful cross-linking of GO with DSAC. The adsorption experiments were well described by the Harkin-Jura model and they followed pseudo-second order kinetics. The maximum adsorption capacity reached 666.67 mg/g at 318 K. Thermodynamic evaluation indicated a spontaneous, feasible, and endothermic in nature. Regenerability and reusability investigations demonstrated that the GO@DSAC composite could be reused for up to 10 desorption-adsorption cycles with a removal efficiency of 81.78%. The selective adsorptive performance of GO@DSAC was examined in a binary system containing Rhodamine B (RhB) and methylene orange (MO). The results showed a separation efficiency (α) of 98.89% for MB/MO and 93.66% for MB/RhB mixtures, underscoring outstanding separation capabilities of the GO@DSAC composite. Overall, the GO@DSAC composite displayed promising potential for the effective removal of cationic dyes from wastewater.

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.

Effective removal of malachite green from local dyeing wastewater using zinc-tungstate based materials

The frequent use of an industrial dye such as malachite green (MG) has caused major water body deterioration and is one of the most pressing global challenges, demanding effective treatment techniques. To solve these issues, a simplistic method was developed to synthesize zinc-tungstate (ZnWO4) nanoparticles and also dope the surface matrix of the ZnWO4 nanoparticles using nonmetals of boron (B), carbon (C), and nitrogen (N) at different ratios for enhanced MG removal from wastewater. The prepared nanomaterials were characterized by different methods for crystal structure composition, surface properties, surface morphology, microstructures, functional groups, and elemental oxidation states. The BET analysis revealed a mesoporous structure with surface areas of 30.740 m2/g for ZnWO4, 38.513 m2/g for ZnWO4@BCN, 37.368 m2/g for ZnWO4@BCN/B, 39.325 m2/g for ZnWO4@BCN/C, and 45.436 m2/g for ZnWO4@BCN/N nanocomposites. The best removal of MG was accomplished at pH (8), contact period (50 min), nanoadsorbent dose (0.8 g/L), initial MG concentration (20 mg/L), and temperature (303 K). The maximum adsorption capacities of ZnWO4 and ZnWO4@BCN/N towards MG were 218.645 and 251.758 mg/g, respectively. At equilibrium, the Freundlich isotherm and pseudo-second-order kinetic models were the best fits for the experimental data of MG adsorption on both nanoadsorbents. After eight cycles of adsorption and desorption, both ZnWO4 and ZnWO4@BCN/N were found to be good at removing MG, with efficiencies of 71.00 and 74.20%, respectively. Thermodynamic investigations further validated the spontaneity and endothermic nature of the adsorption process. All study findings confirm the nanoadsorbents exceptional capability and economic feasibility for removing MG dye.

Significant photocatalytic decomposition of malachite green dye in aqueous solutions utilizing facilely synthesized barium titanate nanoparticles

The release of malachite green dye into water sources has detrimental effects on the liver, kidneys, and respiratory system. Additionally, this dye can impede photosynthesis and disrupt the growth and development of plants. As a result, in this study, barium titanate nanoparticles (BaTiO₃) were facilely synthesized using the Pechini sol-gel method at 600 °C (abbreviated as EA600) and 800 °C (abbreviated as EA800) for the efficient removal of malachite green dye from aqueous media. The Pechini sol-gel method plays a crucial role in the production of barium titanate nanoparticles due to its simplicity and ability to precisely control the crystallite size. The synthesized barium titanate nanoparticles were characterized by several instruments, such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy, and a diffuse reflectance spectrophotometer. The XRD analysis confirmed that the mean crystallite size of the EA600 and EA800 samples is 14.83 and 22.27 nm, respectively. Furthermore, the HR-TEM images confirmed that the EA600 and EA800 samples exhibit irregular and polyhedral structures, with mean diameters of 45.19 and 72.83 nm, respectively. Additionally, the synthesized barium titanate nanoparticles were utilized as catalysts for the effective photocatalytic decomposition of malachite green dye in aqueous media. About 99.27 and 93.94% of 100 mL of 25 mg/L malachite green dye solution were decomposed using 0.05 g of the EA600 and EA800 nanoparticles within 80 min, respectively. The effectiveness of synthesized BaTiO₃ nanoparticles as catalysts stems from their unique characteristics, including small crystallite sizes, a low rate of hole/electron recombination owing to ferroelectric properties, high chemical stability, and the ability to be regenerated and reused multiple times without any loss in efficiency.

Adsorbent biochar derived from corn stalk core for highly efficient removal of bisphenol A

Environmental-friendly biochar (BC) with low cost was obtained by simple pyrolysis of corn stalk core, which was employed as an adsorbent for efficiently removing organic pollutants in water. The physicochemical properties of BCs were characterized by various techniques, including X-ray diffractometer (XRD), Fourier transforms infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Raman, Thermogravimetric (TGA), N₂ adsorption-desorption and zeta potential tests. The influence of pyrolysis temperature on the structure and adsorption efficiency of the adsorbent was emphasized. The graphitization degree and sp² carbon content of BCs were enhanced by increasing the pyrolysis temperature, which was favorable for the enhancement of the adsorption efficiency. The adsorption results showed that corn stalk core calcined at 900 °C (BC-900) displayed exceptional adsorption efficiency toward bisphenol A (BPA) in wide pH (1-13) and temperature (0-90 °C) ranges. Moreover, adsorbent BC-900 could adsorb various pollutants from water, including antibiotics, organic dyes, and phenol (50 mg·L^-1). The adsorption process of BPA over BC-900 matched well with the Langmuir isotherm and pseudo-second-order kinetic model. Mechanism investigation suggested that large specific surface area and pore filling acted the foremost role in the adsorption process. Adsorbent BC-900 has the potential application in wastewater treatment due to its simple preparation, low cost, and excellent adsorption efficiency.

Exploration of Reactive Black 5 Dye Desorption from Composite Hydrogel Beads—Adsorbent Reusability, Kinetic and Equilibrium Isotherms

A low-cost adsorbent was prepared by using cherry stones powder and chitosan and used to retain Reactive Black 5 dye from aqueous solution. Then, the spent material was submitted to a regeneration process. Five different eluents (water, sodium hydroxide, hydrochloric acid, sodium chloride and ethanol) were tested. Among them, sodium hydroxide was selected for an advanced investigation. Values of three working conditions, namely the eluent volume, its concentration and the desorption temperature, were optimized by Response Surface Methodology-Box–Behnken Design. In the established settings (NaOH volume: 30 mL, NaOH concentration: 1.5 M, working temperature: 40 °C), three successive cycles of adsorption/desorption were conducted. The analysis performed by Scanning Electron Microscopy and by Fourier Transform Infrared Spectroscopy revealed the evolution of the adsorbent throughout the dye elution from the material. Pseudo-second-order kinetic model and Freundlich equilibrium isotherm were able to accurately describe the desorption process. Based on the acquired results, our outcomes sustain the suitability of the synthesized material as dye adsorbent and the possibility of efficaciously recycling and reusing it.

Preparation of zirconium oxide nanoparticles from rosette concentrate using two distinct and sequential techniques: hydrothermal and fusion digestion

The preparation of zirconium dioxide nanoparticles (ZrO2-NPs) as hard ceramics was accomplished from rosette zircon concentrate through two consecutive alkaline digestion reactions. The rosette zircon concentration in the Abu Khashaba area consists mainly of zircon and monazite minerals. Using different operating conditions, the hydrothermal digestion by autoclave and the conventional alkaline fusion methods was performed upon the non-magnetic concentrate of rosette in order to complete the removal of monazite firstly and to complete the purification of zircon metal secondly. All monazite content and undesirable impurities were removed by the hydrothermal method using optimal digestion conditions such as 4 mol/L NaOH solutions, 1/6 solid to liquid, 2 h dissolving time, and a temperature of 423 K. The residual zircon (84% Zr) was subjected to complete digestion using NaOH with a zircon-to-alkali ratio of 1/1.5 and a fusion temperature of 923 K. ZrO2-NPs were synthesized using the hydrothermal technique at 473 K for 7 h. The calcined ZrO2-NPs were characterized by X-ray diffraction, scan electron microscope, and transmittance electron microscope. Purified silica was also obtained as a by-product from washing solutions of fused zircon.

The effect of Fe-Zn mole ratio (2:1) bimetallic nanoparticles supported by hydroxyethyl cellulose/graphene oxide for high-efficiency removal of doxycycline

In this research, Hydroxyethyl cellulose - graphene oxide HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1) nanocomposite as adsorbents were fabricated by crosslinking ethylene glycol dimethacrylate (EGDMA) to study the thermodynamic, kinetic and isotherm of doxycycline antibiotic adsorption. The morphology and structure of the adsorbents were analyzed by Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FE-SEM- EDX), and Transmission electron microscopy (TEM). The adsorption behavior of doxycycline (DOX) was studied with different parameters including doxycycline concentration, pH, the dose of adsorbent (HEC-GO and HEC-GO/Fe-Zn, mole ratio (2:1)), contact time, and temperature. The optimal conditions for the removal of DOX are pH = 3.0, contact time 100 min, and 20 min for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1). The removal percentage for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1) was 97% and 95.5%, respectively. Equilibrium adsorption isotherms such as the Langmuir, Freundlich, and Temkin models were analyzed according to the experimental data. Also, four adsorption kinetics were investigated for removing DOX. The Langmuir isotherm and pseudo-second-order kinetic models provided the best fit for experimental data for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1). Thermodynamic data showed that negative values of Gibbs free energy (ΔG°) and the negative value of enthalpy (ΔH°) of the adsorption process for adsorbents. It means that DOX removal was a spontaneous and exothermic reaction.

Structural Properties of Graphene Oxide Prepared from Graphite by Three Different Methods and the Effect on Removal of Cr(VI) from Aqueous Solution

Herein, three types of graphene oxides (GOs, GO-M1, GO-M2 and GO-M3) have been successfully prepared from graphite by three different methods and utilized for the removal of Cr(VI) from aqueous solutions. Further, the effects of initial concentration and pH, adsorbent dosage, contact time and temperature on the adsorption performance of GOs were investigated by batch adsorption experiments. Furthermore, the adsorption mechanisms for Cr(VI) adsorption by GOs are mainly the redox reaction and electrostatic attraction, while there are also pore filling, ion exchange and complexation involved in these adsorption processes. The adsorption kinetic and isotherm data indicate that these adsorption processes of GOs on Cr(VI) are dominantly monolayer chemisorption and equilibrium can be reached in 30 min. The saturation adsorption capacities (Q_m, 298.15 K) of GO-M1, GO-M2 and GO-M3 for Cr(VI) are estimated to be 3.5412 mg⋅g^-1, 2.3631 mg⋅g^-1 and 7.0358 mg⋅g^-1, respectively. Moreover, the adsorption thermodynamic study showed that these adsorption processes of Cr(VI) by the three types of GOs at 298.15 K to 323.15 K are endothermic, entropy-driven and thermodynamically spontaneous and feasible. Overall, these findings provided vital insights into the mechanism and application of Cr(VI) removal by GOs.

Fabrication and implementation of bimetallic Fe/Zn nanoparticles (mole ratio 1:1) loading on hydroxyethylcellulose - Graphene oxide for removal of tetracycline antibiotic from aqueous solution

Tetracycline (TC) as an antibiotic with high consumption causes the spread of contamination in an aqueous solution. In recent decades, antibiotics are the main cause of hindering the growth of microorganisms. Also, they are one of the important groups of pharmaceuticals with extensive usage in human and veterinary medicine. In the first work of its kind, we used a suitable adsorbent of biodegradable hydroxyethylcellulose (HEC) with graphene oxide (GO) by crosslinking ethylene glycol dimethacrylate (EGDMA) and the Fe/Zn with mole ratio 1:1 bimetallic nanoparticles with HEC-GO support. The materials were identified using FTIR, FE-SEM, EDX, TEM, and TG- DSC analyses. The factors affecting the adsorption process (contact time, initial concentration of TC, solution pH, adsorbent dosage, and reaction temperature) were evaluated in a series of batch systems. The adsorption data showed that the high adsorption capacity was obtained on the HEC-GO and HEC-GO/Fe-Zn (mole ratio 1:1) nanocomposites at pH 3. Also, the contact time as the main factor affecting the adsorption process by adsorbents was investigated and the best contact time was 100 and 20 min. The TC removal percentages of both adsorbents were 85% and 95% for HEC-GO and HEC-GO/Fe-Zn, respectively. The maximum adsorption capacity for TC was evaluated by the isotherm models. The experimental data fitted well with the Langmuir model. In addition, pseudo-first-order, pseudo-second-order, intraparticle diffusion, and the Elovich models were applied to kinetic data. The data indicated that TC adsorption on HEC-GO and HEC-GO/Fe-Zn (mole ratio 1:1) followed the pseudo-second-order kinetic model. The thermodynamic parameters implied that the adsorption process was spontaneous and exothermic. Nano-biocomposite (HEC-GO/Fe-Zn) can be used as an adsorbent to remove water pollutants.

Performance of Dye Removal from Single and Binary Component Systems by Adsorption on Composite Hydrogel Beads Derived from Fruits Wastes Entrapped in Natural Polymeric Matrix

The treatment of contaminated water is currently a major concern worldwide. This work was directed towards the preparation of a composite hydrogel by entrapping cherry stones powder on chitosan, which is known as one of the most abundant natural polymers. The synthesized material was characterized by scanning electron microscopy, by Fourier transform infrared spectroscopy, and by the point of zero charge determination. Its ability to remove two azo dyes models (Acid Red 66 and Reactive Black 5) existing in single form and in binary mixture was evaluated. Response Surface Methodology-Central Composite Design was used to optimize three parameters affecting the process while targeting the lowest final contaminant concentrations. The best results were obtained at pH 2, an adsorbent dose of 100 g/L, and a temperature of 30 °C, when more than 90% of the pollutants from the single component systems and more than 70% of those of the binary mixtures were removed from their aqueous solutions. The adsorption process was in accordance with Elovich and pseudo-second-order kinetic models, and closely followed the Freundlich and Temkin equilibrium isotherms. The obtained results led to the conclusion that the prepared hydrogel composite possesses the ability to successfully retain the target molecules and that it can be considered as a viable adsorbent material.

Removal of Dye from Aquatic Environments: State-of-the-Art and Future Perspectives

Surface water sources play a vital role in numerous aspects of societal demand, including as sources of drinking water and water used for agricultural and industrial purposes [...]