Reusability Studies Research Articles

Nutrient recovery from freshwater aquaculture effluent by employing seawater driven zeolite-assisted forward osmosis process

This study focused on recovering nutrients from inland freshwater aquaculture effluent which contains dilute nutrients such as ammonium (NH4+) and phosphate (PO43-) ions. Forward osmosis (FO) process with the assistance of Mg-zeolite Y was employed to recover PO43- through chemical precipitation while NH4+ recovery was achieved by regenerating the zeolite. It showed that zeolite-assisted FO process requires 56.56 ± 2.88 h to dewater 87.5% of the feed solution while standalone FO process took only 51.08 ± 2.99 h. The difference in duration was due to the supplement of Mg2+ that reduces osmotic pressure gradient. The ammonium sorption process of Mg-zeolite Y introduced Mg2+ into the feed solution and facilitated the precipitation of PO43-. Phosphate recovery from the Ca-rich solution from standalone FO process resulted in amorphous calcium phosphate (ACP) with co-precipitation of calcite and dolomite. The zeolite-assisted FO process at pH 10.5 yielded optimal results with 98.46% phosphate recovery, forming mainly amorphous magnesium phosphate (AMP). Subsequently, a two-step precipitation process was proposed to recover Mg2+ as brucite. The concentrated feed solutions from the cycles underwent the proposed two-step precipitation study, resulting in 0.507 g/L of AMP and 5.4077 g/L of brucite. An average of 88.7% NH4+ recovery with high reuse efficiency of Mg-zeolite Y using magnesium sulfate as regenerating solution could be achieved. Reusability studies showed consistent or slightly higher water flux during the dewatering process. The composition of spent regenerant was investigated, and its reuse as liquid fertilizer was feasible after dilution.

Adsorptive performance of a new magnetic hydrochar nanocomposite for highly efficient removal of cadmium ions from water: Mechanism, modeling, and reusability studies

In this study, a novel and effective magnetic watermelon seed hydrochar (MWSHC) was successfully synthesized via hydrothermal carbonization technique and in situ co-precipitation method. The prepared magnetic watermelon seed waste hydrochar has been utilized for the elimination of cadmium ions from the aqueous environment. The structural morphology, surface properties, and thermal stability of MWSHC adsorbent were characterized using FTIR, SEM, XRD, BET surface area, and TGA analysis, which demonstrated the successful synthesis of MWSHC. An extensive study of Cd(II) adsorption was conducted by assessing the influence of contact time, adsorbent mass, pH, initial Cd(II) concentration, temperature, and coexisting cations on the adsorption process of Cd(II). The results revealed that the removal efficiency of Cd(II) was 96.60% achieved at pH 7.0, time: 300 min, and dosage: 0.01 g, T: 298 K. Adsorption isotherm and kinetic parameters were estimated. The results indicated that the Cd(II) adsorption onto MWSHC followed the Freundlich and pseudo-second-order models. Based on the Langmuir equation, the MWSHC has a maximum adsorption capacity of 347.2 mg/g at 298 K. The reusability of magnetic hydrochar nanocomposite was studied, revealing that around 84.4% Cd(II) was still removed after four cycles. In conclusion, the newly- prepared MWSHC adsorbent has the advantages of high adsorption capacity, cost-effectiveness, and easy separation, thus having promising applications in effectively removing cadmium(II) from the aqueous environment.

Rapid adsorption of benzotriazole onto oxidized carbon cloth as an easily separable adsorbent

A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin–Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR.

Bioconversion of starch to Cyclodextrin using Cyclodextrin glycosyltransferase immobilized on metal organic framework

The superiority of a metal organic framework, namely, MIL-101 (Cr) over conventional support, zeolite Y, as immobilization support for Cyclodextrin glycosyltransferase (CGTase) was investigated. The adsorption capacity, stability, and secondary structures of CGTase upon immobilization were investigated. CGTase adsorption on MIL-101 and zeolite Y was best represented by the Langmuir isotherm with optimum adsorption capacities of 37.5 and 6.1 mg/g on two supports, respectively. The deconvolution of the amide I band of the FTIR spectrum indicated that free CGTase molecules predominantly contain β-sheets, which increased with the immobilization on MIL-101 and zeolite Y from 56% to 84.1% and 69.7%, respectively, suggesting the existence of CGTase agglomerates on the supports. The CGTase immobilized on MIL-101 showed relative activity of about 50% at a substrate concentration of up to 4 g/L (compared with free enzymes) and above 3 times higher selectivity towards the more valuable α-CD. A diffusion–reaction model was used to predict the behavior of the immobilized system, and reusability studies revealed that immobilized CGTase may be utilized for numerous reaction cycles, with possible improvements via covalent attachment using glutaraldehyde. Overall, the obtained results in this study provide insights into the usefulness of MIL-101 as a suitable support for CGTase.

Sustainable synthesis of automobile fuel additive from glycerol and acetone and catalyst reusability studies

Sustainable synthesis of automobile fuel additive from glycerol and acetone and catalyst reusability studies

Wet-impregnated niobosilicate catalysts for glycerol conversion into solketal

Novel mesoporous niobosilicate materials with a homogeneous dispersion of niobium species were synthesized via impregnation of (NH4)3[Nb(O2)2(edtaO2)]·H2O·H2O2 on different hydrophilic surfaces of porous siliceous supports: extra small silica nanoparticles (XS-SiO2) and silica nanotubes (NTs-SiO2) bearing three different Si/Nb molar ratios of 74, 37 and 18. The Nb-silica catalysts obtained were calcined at 600 °C and then fully characterized by different physico-chemical techniques. The niobium precursor was found to be successfully loaded on the two silica support surfaces without noticeable modification of the silicate structural integrity. The Nb-containing catalysts were applied as active and selective heterogeneous catalysts for acid-catalyzed condensation of glycerol with acetone yielding solketal (2,2-dimethyl-1,3-dioxolane-4-methanol). The catalytic performance of these materials is ascribed to the enhanced accessibility of their active sites given by their morphology and to the suitable combination of acid sites. Moreover, no leaching of active sites was evidenced and the catalyst reusability studies indicated that the Nb-XS-74 and Nb-NTs-74 catalysts were successfully recyclable and highly stable in the acetalization of glycerol. The robustness and stability of the mesoporous Nb-silicate materials were also supported via characterization of the spent catalysts after the fifth recycling.

Design and development of Carissa edulis fruit extract mediated bimetallic CuO-NiO-HNT composites for photocatalytic removal of food dye and antibiotic drug

The current study demonstrates the synthesis of one dimensional halloysite nanotube (HNT) based CuO-NiO (CN) photocatalyst using green approach via non-conventional microwave and ultrasonication method. Structural, optical, electrochemical, morphological, stability, and surface area characteristics of the synthesised composite were investigated. From the optical studies, the composite exhibited the absorption band edge above 420 nm in the visible region. Electrochemical studies confirmed that 20CN-HNT composited had good charge carrier separation rate compared to CN. Morphological and elemental analysis revealed that the composite was in microsphere structure with even distribution of elements throughout the composite. Congo red (CR- a dye) and tetracycline (TC- a drug) were used to test the composites' photocatalytic efficacy by the irradiation of visible light. Amongst various synthesized composites, 20CN-HNT composite showed good removal efficiency around 82 % and 84 % against CR and TC respectively, in 90 min. The breakdown of CR and TC is caused by the active species •OH and •O2– radicals which was identified using trapping studies. The reusability study demonstrated that the 20CN-HNT photocatalyst retained its high level of stability after being used for five times.

Fabricating modified carbon sesame straw for adsorption of acetaminophen and ibuprofen from aqueous media: isotherm and kinetic models.

As acetaminophen (ACT) and ibuprofen (IBP) have serious environmental impacts, despite their widespread use inmanycountries, the present research examined the effectiveness of activatedcarbonmadefromstraw and sesame stubble in removing ACT and IBPfromwater.To that end, the as-synthesized adsorbent was functionalized using zinc chloride. The maximum adsorption capacitieswere found to be51.7mg g-1 for ACT and 63.7 mg g-1 for IBP. Theadsorptionkineticsandisotherm results showedthatthepseudo-second-order (PSO) kinetics and Langmuir isotherm fit the data obtained from this study betterthanthe otherexperimentalmodels do. Also, the adsorption reached equilibrium within 120 min, and the optimal adsorbent dose and temperature were obtained as 1.0 mg and 25 °C, respectively. The mechanisms involved in the adsorption process would include acid-base, hydrogen bonding, electrostatic forces, and π-π interaction. Reusability studies revealed that the adsorbent still preserved about 89% and 82% of the adsorption performance for ACT and IBP, respectively, after seven repeated adsorption cycles. As the findings indicated, CSS/Zn could be accepted as a hopeful adsorbent to be used in pharmaceutical treatment.

Adsorptive removal of malachite green dye from aqueous solution using Rumex abyssinicus derived activated carbon

The potential for malachite green dye saturated effluent to severely affect the environment and human health has prompted the search for effective treatment technologies. Thus, this study was conducted with the goal of developing activated carbon from Rumex abyssinicus for the adsorptive removal of malachite green dye from an aqueous solution. Unit operations such as drying, size reduction, impregnation with H3PO4, and thermal activation were used during the preparation of the activated carbon. An experiment was designed considering four main variables at their respective three levels: initial dye concentration (50, 100, and 150 mg/L), pH (3, 6, and 9), contact period (20, 40, and 60 min), and adsorbent dosage (0.05, 0.01, and 0.15 g/100 mL). Optimization of the batch adsorption process was carried out using the Response Surface methodology's Box Behnken approach. The characterization of the activated carbon was described by SEM for surface morphology with cracks and highly porous morphology, FTIR for multi-functional groups O–H at 3506.74 cm−1 and 3290.70 cm−1, carbonyl group stretching from aldehyde and ketone (1900–1700 cm−1), stretching motion of aromatic ring C=C (1543.12 cm−1), stretching motion of –C–H (1500–1200 cm−1), vibrational and stretching motion of –OH (1250.79 cm−1), and vibrational motion of C–O–C (1049.32 cm−1), pHpzc of 5.1, BET for the specific surface area of 962.3 m2/g, and XRD for the presence of amorphous structure. The maximum and minimum dye removal efficiencies of 99.9% and 62.4% were observed at their respective experimental conditions of (100 mg/L, 0.10 mg/100 mL, pH 6, and 40 min) and (100 mg/L, 0.15 mg/100 mL, pH 3, and 20 min), respectively. Langmuir, Freundlich, Toth, and Koble-Corrigan models were used to evaluate the experimental data, in which Koble-Corrigan model was found to be the best fit with the highest value of R2 0.998. In addition to this, the kinetic studies were undertaken using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Boyd models, and as a result, the pseudo-second-order model proved to have a better fit among the kinetic models. The kinetics and isotherm analysis revealed that the nature of the adsorption to be homogenous and monolayer surfaces driven by chemosorption. Furthermore, the thermodynamics study revealed the nature of adsorption to be feasible, spontaneous, and endothermic. On the other hand, the reusability study depicted the fact that the adsorbent can be utilized for five cycles with a negligible drop in the removal efficiencies from 99.9 to 95.2%. Finally, the low-cost, environmentally benign, and high adsorption capacity of the adsorbent material derived from Rumex abyssinicus stem could be used to treat industrial effluents.

Nanoarchitectonics of zirconium modified ZnTiO3 for photo and electro-catalysts in dye degradation and water splitting applications

Perovskite oxides are attractive in the catalytic application owing to their stability, tuning characteristics, and easy synthesis process. Here, ZnTi1-xZrxO3 (x = 0.5) (abbreviated as ZZT0.5) is synthesized under the chemical precursor solution decomposition method and calcined at 700 °C for 3 h. The cubic phase nanosized material exhibits cubic shape morphology with the proper ratio of the existing elements as from observed structural and morphological characterizations. In the photocatalytic dye degradation under natural sunlight irradiation, the materials show >90% color degradation of congo red and murexide. The observed result in the presence of solar light irradiation highlights an elevated photocatalytic efficiency. The pseudo-first-order degradation process shows a high correlation coefficient with good stability of the material in the reusable study. This ZnTiO3-based perovskite material has not been used previously in electrocatalytic water splitting. During oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) conditions, the material deposited on NF substrate showed 335 mV and 165 mV overpotential at 10 mA cm−2 current density, respectively which is indicative of notable electrocatalytic water splitting activity of the perovskite material designed herein. The long-term chronoamperometry (CA) study confirms the material's stability during both HER and OER conditions with negligible loss in activity over a period of 12 h. The post-catalytic characterizations confirm the robust nature of the material possessing the same phase characteristics. As an earth-abundant, low-cost material, the material designed herein shows the significant activity of environmental sustainability in terms of water treatment as well as green hydrogen production via electrolysis.

Plant-based synthesis of TiO2 – rGO nanocomposite for the efficient photocatalytic degradation of an emerging contaminant: Experimental and theoretical investigations

The need to develop sustainable and efficient photocatalysts for the degradation of contaminants of emerging concern has gained considerable attention. In this study, plant-based titanium dioxide-reduced graphene oxide (TiO2-rGO) photocatalyst was synthesized by a hydrothermal method using Azadirachta indica (AI) leaf extract. Morphological and chemical properties of the AI-TiO2-rGO photocatalyst were evaluated in detail. The clusters of AI-TiO2 wrapped in AI-rGO were identified with TEM analysis, and from the XRD, the purity of AI-TiO2-rGO was confirmed. The low band gap (2.80 eV) of AI-TiO2-rGO made it a suitable photocatalyst under visible light. The X-ray photoelectron spectroscopy (XPS) results indicated the establishment of strong Ti-O-C chemical linkage within the AI-TiO2-rGO photocatalyst. The efficiency of AI-TiO2-rGO was assessed for the degradation of carbamazepine (CBZ) under UV-A irradiation (94.28%) and visible light (59.97%) in a batch photocatalytic reactor for 60 min. The optimized conditions such as AI-TiO2-rGO dosage (50 mg/L), initial CBZ concentration (4.5 mg/L), and light source (UV-A (60 W)), were validated with response surface methodology (RSM). The mechanism of degradation of CBZ by AI-TiO2-rGO was explained with the identification of intermediate compounds, and three plausible CBZ degradation pathways were proposed. The reusability study suggested that the AI-TiO2-rGO photocatalyst could be effectively used for 8 cycles. The evaluation of toxicity of treated water with E.Coli growth curve (reduction in Iind to 30.12% (UV) and 27.65% (visible)) signified that the treated water was less toxic. The comparison of AI-TiO2-rGO with chemically synthesized TiO2-rGO indicated that even though AI-TiO2-rGO exhibited a slightly higher band gap (2.80 eV), it can be the better alternative for the photocatalysts synthesized by chemical route. The economic analysis of the overall process proved that the application of AI-TiO2-rGO was more cost-effective and sustainable than the conventional TiO2 photocatalyst. Overall, the study provides valuable insight into synthesizing recyclable plant-based photocatalysts to degrade recalcitrant emerging contaminants in the water.

The Role of Biocomposites and Nanocomposites in Eliminating Organic Contaminants from Effluents

Many contaminants such as heavy metals, dyes and hydrocarbon compounds are annually generated by industrial activities and discharged into water sources. They have destructive impacts on the environment. To eliminate these toxic contaminants from aqueous media, sorption can be considered a proper and efficient process, as it has indicated high efficiency for removing organic contaminants. This paper entails a comprehensive evaluation of different organic pollutants, pros and cons of the sorption process in removing these pollutants, comparing different types of adsorbents and investigating the recyclability of different types of composites. Moreover, the sorption mechanism and kinetic behavior of organic contaminants are investigated using biocomposites and nanocomposites. Moreover, the future perspectives of biocomposites and nanocomposites in eliminating organic compounds are discussed. Based on investigations, a large number of nanocomposites have been utilized for removing organic contaminants with high performance so far, including SiO2/MnFe2O4/ZIF-8 MOF, magnetite/MWCNTs, nano zerovalent iron, barium/Cobalt/polyethylene glycol (PEG), graphene oxide/Fe3O4, kaolin/CuFe2O4 and Fe3O4@UiO-66. Moreover, polyaniline/sodium alginate/Oscillatoria filamentous cyanobacterium biomass, cow bones/zeolite/coconut biocomposite and AC derived from melamine and sucrose are excellent biocomposites in the removal of organic pollutants. Moreover, the reusability study shows that poly(N-isopropylacrylamide)/Fe3O4 and corn stalk biomass/chitosan/Fe3O4 biocomposites have significant stability compared to other composites in the elimination of organic pollutants.

A novel bimetallic (Au-Pd)-decorated reduced graphene oxide nanocomposite enhanced Rhodamine B photocatalytic degradation under solar irradiation

Nowadays, water quality is one of the main challenges facing humanity. Recently, hybrid nanomaterials have attracted great attention because they can treat water solutions. In this study, Sol-Immobilization synthesized monometallic (Pd and Au) and bimetallic (Pd-Au) hybrid nanomaterials supported on reduced graphene oxide (rGO) were synthesized as catalysts for the photocatalytic Rhodamine B degradation under direct sunlight. The as-synthesized nanomaterials were characterized using XRD, Raman spectroscopy, UV-DRS spectrophotometer, HR-TEM techniques, and X-ray Photoelectron Spectroscopy. The catalytic activities of Pd/rGO and Au/rGO were compared with those of Aux-Pdy/rGO, and a higher photocatalytic degradation efficiency was found for the bimetallic-supported rGO sample. At optimum conditions, Au0.75-Pd0.25/rGO achieved the best dye degradation efficiency of 98%. The reusability study results showed that Au0.75-Pd0.25/rGO retained 89% of its initial activity after five successive uses. The scavenging study results proved that hydroxyl radicals are the major reactive species in the photocatalytic degradation reaction. These findings indicate that Au0.75-Pd0.25/rGO catalyst is a promising material for the treatment of water contaminated with organic dyes under sunlight.

Experimental investigation of H3PO4 activated papaya peels for methylene blue dye removal from aqueous solution: Evaluation on optimization, kinetics, isotherm, thermodynamics, and reusability studies

This investigation is centered on the effectiveness of methylene blue (MB), a cationic dye, adsorbed from an aqueous media by H3PO4 activated papaya skin/peels (PSPAC), with initial pH (2–10), contact time (30–180 min), MB dye concentration (varying from 10 to 50 mg/L), and MB dose (0.1–0.5 gm). The findings show that the best optimal conditions for MB dye removal occur at a 6 pH, 0.3 gm dose of PSPAC adsorbent for 10 mg/L MB dye concentration, with 90 min of contact time. To optimize and validate the extraction efficiency of MB dye, a response surface methodology (RSM) study was conducted using a central composite design (CCD) with a regression model showing R2 = 0.9940. FT-IR spectroscopy shows, CO, and O–H stretching functional groups while FE-SEM is assessed to supervise morphological features of the PSPAC adsorbent. The peak adsorption capacity with 46.95 mg/g for the Langmuir isotherm model conveniently satisfies the adsorption process with R2 = 0.9984 while with R2 = 0.999, a kinetic model, pseudo-second-order, confirms MB dye adsorption by PSPAC adsorbent. Moreover, thermodynamic parameters including ΔGᵒ, ΔH°, and ΔS° were computed and found to be spontaneous and exothermic. Furthermore, regeneration studies employed with NaOH (0.1 M) and HCl (0.1 M) solution media show an acceptable MB removal efficiency consecutive up to three cycles. The study highlights that H3PO4 papaya skin/peel (PSPAC) is an effectual, sustainable, reasonably available biosorbent to remove industrial cationic dyes disposal.

Fabrication of biogenic carbon-based materials from coconut husk for the eradication of dye

The highly biocompatible nature of carbon dots (CQDs) and potential usage in waste water treatment makes them as one of the effective alternative for treating water pollution. Herein, biogenic carbon dots (CQDs) with size range of 2 nm were prepared from waste coconut husk as a precursor source. The hydrophilic nature and higher surface area of as prepared CQDs has further supported the superior adsorption efficiency of more than 90% for Victoria blue B (VB) dye from waste water samples. Different dye adsorption parameters including adsorbate and adsorbent dosage, pH of reaction media and equilibrium time have been optimized and found that 8 mg of adsorbent was sufficient to remove 70 mg VB dye in 4 mL aqueous solution in 60 min at pH = 7. The adsorption kinetic (2nd order) and isotherms (Freundlich-type) were well followed on prepared CQDs. The reusability studies up to 5 times with minimal decrement of 4% confirm the constancy of CQDs for the adsorptive removal of VB. The methodology presents a greener way for overcoming ecological issues with sustainable materials in an economical manner.

Two-Stage Conversion of Used Cooking Oil to Biodiesel Using Ion Exchange Resins as Catalysts

This study focuses on the development of a novel two-stage (esterification–transesterification) synthesis of biodiesel from used cooking oil (UCO) using ion exchange resins as catalysts. Esterification of the UCO has been conducted using various types of ion exchange resin catalysts. Purolite D5081, a hyper cross-linked resin, showed the best catalytic performance among all the catalysts investigated, with 92% of free fatty acid (FFA) conversion. The transesterification of pre-treated used cooking oil (P-UCO) was carried out sequentially using several acidic and basic ion exchange resin catalysts. In the screening process, the Diaion PA306s catalyst showed the best catalytic performance and was selected for the optimisation study. A triglyceride conversion of ca. 75% was recorded at the optimum reaction conditions (9% (w/w) catalyst loading, 328 K reaction temperature, 18:1 methanol to P-UCO feed mole ratio, and 350 rpm stirring speed). Furthermore, the reusability study of the Diaion PA306s catalyst gave a similar triglyceride conversion after a couple of cycles without losing its catalytic activity. A dry purification technique was found to give the lowest percentage of glycerides and glycerine content and, therefore, was chosen as the best biodiesel purification route.

Key parameters for enhancing visible-light-driven photocatalytic activity of ZnS nanoparticle

The use of pharmaceuticals is increasing rapidly as the industrialization of the pharmaceutical industry progresses. Accordingly, antibiotics discharged into wastewater are attracting attention as emerging pollutants that aggravate water pollution. The spread of antibiotic-resistant bacteria that cause clinically infectious diseases is also a global challenge. In this study, ZnS nanoparticles were synthesized using a simple hydrothermal process and applied to the photocatalytic degradation of antibiotic tetracycline and the photocatalytic inactivation of high-strength multidrug-resistant bacteria (Klebsiella pneumonia and Staphylococcus aureus) and total coliforms under visible light irradiation. The prepared nanomaterial was characterized using a range of analytical techniques to confirm the properties of the ZnS nanoparticles. The photocatalytic activities of nanoparticles were investigated with various parameters, such as catalyst dose, type and intensity of light, antibiotic concentration, and pH. Among them, the type of light (white light) and pH were the most important factors affecting the photocatalytic activity of ZnS nanoparticles. The basic pH condition (pH 10) improved the photocatalytic reaction activity (k = 0.0318 min−1, R2 = 0.9653), approximately 30 times more than acidic conditions (pH 3) and approximately 3.3 times more than neutral conditions (pH 7). The total coliforms in wastewater effluent were completely inactivated within 30 min of reaction time using white light irradiation (80 mW/cm2). The scavenger experiment revealed that the reactive oxygen species appeared in the order of O2·− > ·OH > h+. The reusability studies showed that the ZnS nanoparticles were very stable and retained more than 94% of their catalytic capacity after five cycles.

A synergistic approach combining Adsorption and Biodegradation for effective treatment of Acid Blue 113 dye by Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel Beads

This study investigated the degradation of Acid Blue 113 (AB 113) dye using Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel beads (KG-GO-CA) in a Fluidized Bed Bioreactor (FBBR) under varying inlet loading rates. The minimum fluidization velocity of the KG-GO-CA hydrogel beads in FBBR was found to be 0.15 mm/s. The KG-GO-CA beads showed a maximum removal efficiency of 94.6% at an inlet flow rate of 20 mL/h over 15 days. Reusability studies indicated a removal efficiency of 70.6 ± 2.5% for AB 113 after the 12th cycle. Langmuir adsorption isotherm showed the best fit (R2 = 0.98724) with model parameters of Qm (203.83 mg/g) and Ki (0.0101 L/g). The study also confirmed that treated wastewater was more environmentally safe for domestic and commercial uses than untreated wastewater. The research highlights the potential use of KG-GO-CA hydrogel beads for removing dyes from wastewater.

A cleaner approach with magnetically assisted reactor setup over CaO-zeolite/Fe3O4 catalyst in biodiesel production: Evaluation of catalytic performance, reusability and life cycle assessment studies

This study reports the magnetic catalyst constructed by incorporating magnetite (Fe3O4) within zeolite-supported calcium oxide (CaO) in conventional and magnetic reactors for heterogeneous catalytic biodiesel production. The CaO-zeolite/Fe3O4 catalyst demonstrated remarkable characteristics, including a substantial surface area, acid-base properties, and high magnetization. These attributes enable efficient transesterification of used cooking oil (UCO) with high free fatty acid (FFA) content and facilitate the easy separation of the solid catalyst by utilizing magnetic force once the reaction is complete. In the conventional reactor, employing a 3 wt% catalyst dosage and a 5:1 methanol to oil molar ratio, the maximum biodiesel yield reached 93.64% after 240 min at 55 °C. Meanwhile, the magnetic reactor yielded a maximum biodiesel yield of 96.91% when operating for 300 min, using a 4 wt% catalyst dosage, 5:1 methanol to oil molar ratio, and maintaining a reaction temperature of 55 °C. The catalyst reusability result did not indicate an appreciable reduction in biodiesel yield in 4 cycles with the magnetic reactor. The life cycle assessment (LCA) study also revealed fewer negative effects of biodiesel production by using a magnetic reactor on the environment. The efficient utilization of CaO-zeolite/Fe3O4 catalyst in the magnetic reactor has shown great potential for industrial application.

β-Cyclodextrin magnetic graphene oxide (β-CD@MGO) for efficient removal of Ni(II) and phenol: Adsorption performance, reusability and adsorption mechanism studies

Pollutants in the wanton discharge of wastewater have seriously threatened the ecosystem on which human beings depend, so the treatment of wastewater is very necessary. In this work, a novel recyclable high-efficiency treatment material, β-cyclodextrin magnetic graphene oxide (β-CD@MGO), was prepared for the removal of Ni(II) and phenol in wastewater. A variety of research methods were used to explore the micro- and macro-structure of the material, and the removal efficiency of the material for Ni(II) and phenol was explored under various conditions. Under optimal conditions, the maximum adsorption capacities of Ni(II) and phenol were 272 mg/g and 233 mg/g, respectively. In addition, the pseudo-first-order model was found to be most consistent with the kinetic data through the kinetic fitting, the Langmuir isotherm model in the isotherm study, as well as the thermodynamic exploration showed that the adsorption was a spontaneous exothermic and a monolayer physical adsorption process. For the recovery experiment, the maximum adsorption capacity of the adsorbent for pollutants remained above 88% after 6 cycles. Finally, the mechanism of adsorption is also discussed, and it is found that the host-guest interaction can be used to explain the adsorption, and physical adsorption is dominant. In summary, the material has a relatively good adsorption effect on Ni(II) and phenol, and is expected to be used in future adsorption projects.