Microwave modified sugar cane bagasse cellulose as an eco-friendly biosorbent for eliminating As(V) from aqueous medium

This work explores the potential of microwave assisted urea modified sugarcane bagasse (UMSCB) as an effective, environment-friendly biosorbent for removing As(V) from an aqueous medium. The synthesized biomaterial was characterized by FTIR analysis that showed the existence of various carboxyl, hydroxyl, and carbonyl functional groups; and SEM analysis of UMSCB showed much higher roughness before the As(V) adsorption of 40.78; indicating that As(V) intricately gets adsorbed onto surface of UMSCB. Batch adsorption experiments demonstrated a removal efficiency of approximately 95 % within 30 min at pH 5. However, UMSCB follows pseudo-second-order kinetics and chemisorption mechanism for removal of As(V). The intra-particle diffusion model indicated that more than one step influences the rate-limiting step. Adsorption equilibrium data shows that the Langmuir model provided the best fit, as determined by correlation coefficient (R2) and chi-square (χ2). Notably, the adsorption capacity (qe) of unmodified sugarcane bagasse (SCB) significantly increased from 4.8 mg/g to 52.8 mg/g upon microwave-assisted urea modification, demonstrating the substantial enhancement in As(V) uptake. Thermodynamic indicators indicated that the biosorption is spontaneous, endothermic, and feasible. The high adsorption efficiency, ease of regeneration, and potential for large-scale application highlight UMSCB as a promising solution for As(V) removal from wastewater.

Tactical metal-organic frameworks (MOFs) adsorbent advantages in removal applications

Water pollution caused by the increasing concentration of toxic chemicals, such as heavy metal ions, pesticides, pharmaceutical waste, and plastic contaminants, has become a global issue. The rising levels of these pollutants pose significant health risks to humans and various species. Recently, adsorption has emerged as a promising method for removing these contaminants. This review focuses on metal-organic frameworks (MOFs) as adsorbents, highlighting their large surface areas and adjustable porosity, which optimize the adsorption process. The review analyzes the active sites within MOFs, their roles in adsorption mechanisms, and the underlying chemistry involved. It also discusses the structural chemistry of MOFs and its impact on pollutant removal efficiency. Furthermore, the review addresses stability, scalability, and economic feasibility challenges. Finally, it suggests future research directions for next-generation MOF materials to enhance their effectiveness in sustainable environmental remediation, ultimately improving our ability to combat contamination issues and protect healthy ecosystems.

Synthesis of a novel multifunctional organic-inorganic nanocomposite for metal ions and organic dye removals

In this study, we used solvent assisted mechano-synthesis strategies to form multifunctional organic-inorganic nanocomposites capable of removing both organic and inorganic contaminants. A zeolite X (Ze) and activated carbon (AC) composite was synthesized via state-of-the-art mechanical mixing in the presence of few drops of water to form Ze/AC. The second composite (Ze/L/AC) was synthesized in a similar fashion, however this composite had the addition of disodium terephthalate as a linker. Both materials, Ze/AC and Ze/L/AC, were characterized using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Powdered X-ray diffraction (P-XRD), Fourier-transform infrared spectrometry (FTIR), Accelerated Surface Area and Porosimetry System (ASAP), and thermal gravimetric analysis (TGA). The SEM-EDS displayed the surface structure and composition of each material. The sodium, oxygen and carbon contents increased after linker connected Ze and AC. The P-XRD confirmed the crystallinity of each material as well as the composites, while FTIR indicated the function groups (C=C, O-H) in Ze/L/AC. The contaminant adsorption experiments investigated the effects of pH, temperature, and ionic strength on the adsorption of methylene blue (MB) and Co(II) for each material. In MB adsorption, the first-order reaction rate of Ze/L/AC (0.02 h-1) was double that of Ze/AC (0.01 h-1). The reaction rate of Ze/L/AC (4.8 h-1) was also extraordinarily higher than that of Ze/AC (0.6 h-1) in the adsorption of Co(II). Ze/L/AC composite achieved a maximum adsorption capacity of 44.8 mg/g for MB and 66.6 mg/g for Co(II) ions. The MB adsorption of Ze/AC and Ze/L/AC was best fit in Freundlich model with R2 of 0.96 and 0.97, respectively, which indicated the multilayer adsorption. In the Co(II) adsorption, the data was highly fit in Langmuir model with R2 of 0.94 and 0.92 which indicated the monolayer adsorption. These results indicated both materials exhibited chemisorption. The activation energy of Ze/L/AC in MB adsorption (34.9 kJ mol-1) was higher than that of Ze/L/AC in Co (II) adsorption (26 kJ mol-1).

Synthesis, Characterization and Decomposition of Potassium Jarosite for Adsorptive As(V) Removal in Contaminated Water: Preliminary Study

Jarosite-type compounds precipitated in the zinc industry for iron control can also incorporate arsenic and can be used for wastewater treatment for As elimination. According with the last, this work is related to arsenic incorporation at room temperature in decomposed potassium jarosite. The work began with the synthesis of the compound at 75 °C for 9 h using Fe₂(SO₄)₃ and K₂SO₄ at a pH of 1.1. Once jarosite was obtained, solids were subjected to an alkaline decomposition using NaOH at pH 10 for 30 min, and then As was added to the solution as HAsNaO₄ and the pH modified by adding HNO₃ until it reached a value of 1.1. The initial, intermediate, and final products were wholly characterized by scanning electron microscopy (SEM) in conjunction with energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS), and X-ray photoelectron spectrometry (XPS). The obtained results show that As(V) can be adsorbed by ionic exchange in the amorphous FeOH structure of decomposed jarosite and when pH decreased to 1.1, the compound recrystallized, incorporating up to 6% As on average, which is indicative that this process can be used to reduce As in contaminated waters.

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

For the first time, the presence of acetone in the casting solutions of polyacrylonitrile (PAN) in dimethylsulfoxide or N-methyl-2-pyrrolidone was studied with regards to thermodynamical aspects of phase separation of polymeric solutions induced by contact with non-solvent (water), formation and performance of porous membranes of ultrafiltration range. The positions of the liquid equilibrium binodals on the phase diagrams of these three-component and pseudo-three-component mixtures were determined. For PAN-N-methyl-2-pyrrolidone-water glass transition curve on a ternary phase diagram was plotted experimentally for the first time. The real-time evolution of the structure of mixtures of PAN with solvents (co-solvents) upon contact with a non-solvent (water) has been studied. The thermodynamic analysis of the phase diagrams of these mixtures, together with optical data, made it possible to propose a mechanism of structure formation during non-solvent induced phase separation of different mixtures. The addition of acetone promotes the formation of a spongy layer on the membrane surface, which decreases the probability of defect formation on the membrane surface and keeps finger-like macrovoids from the underlying layers of the membrane. It was shown that the molecular weight cut-off (MWCO) of the membranes can be improved from 58 down to 1.8 kg/mol by changing the acetone content, while polymer concentration remained the same.

Headspace Extraction of Chlorobenzenes from Water Using Electrospun Nanofibers Fabricated with Calix[4]arene-Doped Polyurethane-Polysulfone

Chlorobenzenes (CBs) are persistent and potentially have a carcinogenic effect on mammals. Thus, the determination of CBs is essential for human health. Hence, in this study, novel polyurethane−polysulfone/calix[4]arene (PU-PSU/calix[4]arene) nanofibers were synthesized using an electrospinning approach over in-situ coating on a stainless-steel wire. The nanosorbent was comprehensively characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) techniques. The SEM analysis depicted the nanofiber’s unique morphology and size distribution in the range of 50−200 nm. To determine the levels of 1,2,4-trichlorobenzene, 1,2,3-trichlorobenzene, and 1,2,3,4-tetrachlorobenzene in water samples, freshly prepared nanosorbent was employed using headspace-solid phase microextraction (HS-SPME) in combination with gas chromatography micro electron capture detector (GC-µECD). Other calixarenes, such as sulfonated calix[4]arene, p-tert-calixarene, and calix[6]arene were also examined, and among the fabricated sorbents, the PU−PSU/calix[4]arene showed the highest efficiency. The key variables of the procedure, including ionic strength, extraction temperature, extraction duration, and desorption conditions were examined. Under optimal conditions, the LOD (0.1−1.0 pg mL−1), the LDR (0.4−1000 pg mL−1), and the R2 > 0.990 were determined. Additionally, the repeatability from fiber to fiber and the intra-day and inter-day reproducibility were determined to be 1.4−6.0, 4.7−10.1, and 0.9−9.7%, respectively. The nanofiber adsorption capacity was found to be 670−720 pg/g for CBs at an initial concentration of 400 pg mL−1. A satisfactory recovery of 80−106% was attained when the suggested method’s application for detecting chlorobenzenes (CBs) in tap water, river water, sewage water, and industrial water was assessed.

Adopting Sustainable Jatropha Oil Bio-Based Polymer Membranes as Alternatives for Environmental Remediation

This study aimed to optimize the removal of Cu(II) ions from an aqueous solution using a Jatropha oil bio-based membrane blended with 0.50 wt% graphene oxide (JPU/GO 0.50 wt%) using a central composite model (CCD) design using response surface methodology. The input factors were the feed concentration (60–140) ppm, pressure (1.5–2.5) bar, and solution pH value (3–5). An optimum Cu(II) ions removal of 87% was predicted at 116 ppm feed concentration, 1.5 bar pressure, and pH 3.7, while the validated experimental result recorded 80% Cu(II) ions removal, with 95% of prediction intervals. A statistically non-significant term was removed from the analysis by the backward elimination method to improve the model’s accuracy. Using the reduction method, the predicted R² value was increased from −0.16 (−16%) to 0.88 (88%), suggesting that the reduced model had a good predictive ability. The quadratic regression model was significant (R² = 0.98) for the optimization prediction. Therefore, the results from the reduction model implied acceptable membrane performance, offering a better process optimization for Cu(II) ions removal.

New approach for starch dialdehyde preparation using microwave irradiation for removal of heavy metal ions from water

This work presents a new and simple approach to prepare Dialdehyde Starch (DAS) in one step under microwave irradiations and using, a mild and safer oxidizing agent, potassium iodate. Aldehyde content was evaluated to compare the synthesis results with DAS prepared using potassium periodate as an oxidizing agent for starch. To optimize the synthesis parameters of the new approach, the effect of the quantity of oxidizing agent and the effect of reaction time on the content of aldehyde in DAS were evaluated. According to the results, the optimized time was 10 min at the power of 300 W, and the number of moles of oxidizing agent was 0.014 mol per 2 g of starch. After that, DAS was used to prepare two Schiff bases by reaction with urea (DASU) and thiourea (DASTU), respectively. DAS, DASU and DASTU were characterized by FTIR, XRD, and SEM. Furthermore, DAS, DASU and DASTU were investigated for removing Cu(II), Pb(II), Hg(II), Cd(II), and Cr(III) ions from water. DAS showed the highest removal efficiency towards Pb(II) ions, whereas DASTU exhibited excellent ability for removing the Hg(II) ions. The removal efficiencies of DAS for Pb(II) ions and DASTU for Hg(II) ions are 95.25% and 89.45%, respectively from aqueous solutions containing 100 ppm of respective ions. Adsorption isotherm study suggests that adsorption follows Langmuir isotherm model, (correlation factors (R2) for Langmuir and Freundlich models for DAS/Pb are equal to 0.984 and 0.799, respectively, and for DASTU/Hg they are 0.995 and 0.813, respectively). The theoretical maximum adsorption capacity for DAS/Pb and DASTU/Hg are 245.09 and 180.83 mg/g, respectively.

Cr(VI) Adsorption from Aqueous Solution by UiO-66 Modified Corncob

To adsorb hexavalent chromium (Cr(VI)) in polluted water, this paper prepared a UiO-66 (Zr6O4(OH)4(BDC)12) modified granular corncob composite adsorbent by hydrothermal method with in situ loading of UiO-66 on pretreated corncob particles. The physicochemical properties of the synthesized samples were characterized. Batch adsorption experiments were conducted to investigate the adsorption process of aqueous Cr(VI) under various conditions (different ionic strength, pH and co-existing anions). The results showed that UiO-66 was successfully loaded on the modified corncob particles. The isothermal adsorption data of Cr(VI) adsorption by the UiO-66 modified corncob fit well with the Langmuir model with the maximum adsorption capacity of Cr(VI) on UiO-66@Corn+ being 90.04 mg/g. UiO-66 loading could increase Cr(VI) adsorption capacity of Corn+. The kinetic study showed that the equilibrium time for Cr(VI) adsorption on UiO-66 modified corncob was about 180 min and the kinetic data followed the pseudo-secondary kinetic model. The Cr(VI) adsorption capacity on UiO-66@Corn+ decreased with the increasing solution pH, and the optimum pH range was 4–6. The ionic strength has little effect on the Cr(VI) adsorption capacity, but the coexistence of CO32−, SO42− and PO43− in the solution could significantly decrease the equilibrium adsorption capacity of Cr(VI). The adsorption mechanism analysis showed that Cr(VI) was adsorbed on the surface of adsorbents through electrostatic attraction and was reduced further to the less toxic Cr(III) by the electron donor on the surface of adsorbent. The electrostatic interaction was the main force affecting the adsorption of Cr(VI) by UiO-66. UiO-66@Corn+ had an excellent removal efficiency of Cr(VI) and excellent reusability. UiO-66@Corn+ could effectively remove Cr(VI) from water and have a promising application.