Adsorption and detection of heavy metals from aqueous water by PVDF/ATP-CDs composite membrane

Utilization of peanut hull hydrochar /beta cyclodextrin/Fe3O4 magnetic composite for lead ion removal from water solution

This study involves synthesizing peanut hull hydrochar (PHH) and a PHH/β-CD/Fe3O4 magnetic composite through hydrothermal and chemical precipitation methods, respectively, to use as effective adsorbents for Pb2+ removal. Vibrating-sample magnetometry (VSM) and Brunauer-Emmett-Teller (BET) analyses revealed that the magnetic saturation value and specific active surface area of PHH/β-CD/Fe3O4 are 31.543 emu/g and 32.123 m2/g, respectively. The impact of key variables on adsorption efficiency was evaluated using the response surface method - central composite design. ANOVA results (F-value: 166.22 and p-value: <0.05) demonstrated that the model effectively assesses the interaction of variables in the adsorption process. Additionally, R2, Adjusted R2, and Predicted R2 values were 0.999, 0.986, and 0.975, respectively, indicating the model's high adequacy in describing response changes. The maximum efficiency for Pb2+ adsorption was found to be 95.35% using PHH and 99.73% with the PHH/β-CD/Fe3O4 magnetic composite. These measurements were taken at a temperature of 25 °C, an adsorbent dose of 1 g/L, a pH of 6, and a Pb2+ concentration of 5 mg/L, with respective contact times of 130 min and 50 min. Thermodynamic analysis revealed negative enthalpy and Gibbs free energy values, indicating that the adsorption process is exothermic and spontaneous. The negative entropy parameter suggests a reduction in random interactions during the process. The Pb2+ adsorption data for both PHH (R2: 0.982) and PHH/β-CD/Fe3O4 (R2: 0.985) were best described by the Pseudo 2nd order kinetic model. Equilibrium data followed the Freundlich model, with R2 values of 0.981 for PHH and 0.990 for PHH/β-CD/Fe3O4, highlighting the importance of heterogeneous surfaces in the removal process. The maximum adsorption capacities for Pb2+ were 26.72 mg/g for PHH and 33.88 mg/g for PHH/β-CD/Fe3O4. Reuse and stability tests confirmed the structural stability and reusability of the adsorbents. Therefore, the PHH/β-CD/Fe3O4 magnetic composite is a promising option for removing Pb2+ from aqueous solutions.

Fabrication of nitrogen-doped carbon dots biomass composite hydrogel for adsorption of Cu (II) in wastewater or soil and DFT simulation for adsorption mechanism

With the increase of Cu (II) content, its bioaccumulation becomes a potential pollution to the environment. It is necessary to design an economical and efficient material to remove Cu (II) without causing other environmental hazards. A novel material of alginate composite bead (ALG@NCDs) was synthesized by embedding N-doped carbon dots into pure alginate bead for the adsorption of Cu (II) from wastewater and contaminated soil. The initial concentration, the amount of adsorbent, temperature, adsorption time, and pH value were optimized for the adsorption of Cu (II). According to the Langmuir isothermal adsorption model, the maximum adsorption amount of the material to Cu (II) was 152.44 mg/g. The results of selective adsorption showed that ALG@NCDs had higher affinity to Cu (II) than to Pb (II), Co (II), Ni (II), and Zn (II). After five adsorption-desorption experiment, adsorption capacity of the ALG@NCDs was kept 89% of the initial adsorption capacity. Its Cu (II) adsorption mechanism was studied by density functional theory calculations. In addition, the material could effectively adsorb Cu (II) and release the phytonutrient Ca (II) simultaneously when applied to actual wastewater and soil. The fabricated ALG@NCDs would be a promising material for the adsorption of Cu (II) from wastewater or soil.

Modified coconut shell biochars (MCSBCs): Fabrication and their adsorptions for Pb(II)

The modified coconut shell biochars (MCSBCs) were fabricated and their adsorptions for Pb(II) were evaluated, in which waste coconut shell was used as the raw material, both ZnCl2 and KMnO4 were applied as the inorganic modifiers. FT-IR spectra, TGA, SEM and BET techniques were utilized to characterize their properties. It was spotted that the thermal stability of UCSBC could arrive at 500 °C. The BET specific surface areas of both Zn- and Mn-modified MCSBCs (485.137, 476.734 m2/g) were highly decreased as compared with that of UCSBC (3528.78 m2/g). In contrast, the average pore diameters of both Zn- and Mn-modified MCSBCs (3.295, 3.803 nm) were smaller than that of UCSBC (3.814 nm). These findings reveal that the modification of CSBC didn't change its pore size. Their adsorptions for Pb(II) were performed and some controlling factors involving pH, contact time, starting concentration and temperature were explored. Moreover, the experiment data were fitted via linear and non-linear techniques. It was found that the Langmuir maximal adsorption amounts of un-modified coconut shell biochar (UCSBC), Zn-modified and Mn-modified MCSBCs for Pb(II) could reach 31.653, 86.547 and 93.666 mg/g, respectively. Two-parameter kinetic models exposed that Pb(II) adsorption on UCSBC, Zn-modified and Mn-modified MCSBCs obeyed both the Lagergren first-order (non-linear R2 = 0.990, 0.954, 0.953, respectively) and Avrami fractional-order (non-linear R2 = 0.989, 0.946, 0.945, respectively) kinetic models. Two-parameter and three-parameter isotherm models verified that Pb(II) adsorption on UCSBC, Zn-modified and Mn-modified MCSBCs followed the Langmuir (non-linear R2 = 0.992, 0.997, 0.993, respectively) as well as Sips (non-linear R2 = 0.992, 0.997, 0.992, respectively) isotherm models. The computation of thermodynamic parameters evidenced that the modification of UCSBC via KMnO4 and ZnCl2 can effectively rise its adsorption for Pb(II), exhibiting promising applications in the handling of metal-bearing water.

Efficient removal of methyl orange and ciprofloxacin by reusable Eu-TiO2/PVDF membranes with adsorption and photocatalysis methods

The presence of methyl orange (MO) and ciprofloxacin (CIP) in wastewater poses a serious threat to the environment and human health. Titanium dioxide nanoparticles (TiO2 NPs) are widely studied as photocatalysts for wastewater treatment. However, TiO2 NPs have the drawbacks of high energy required for activation, fast electron-hole pair recombination and difficulty in recovering from water. To overcome these problems, europium decorated titanium dioxide/poly(vinylidene fluoride) (Eu-TiO2/PVDF) membranes were successful prepared in this work by combining the modified sol-gel method and the immersion phase inversion method. The Eu-TiO2/PVDF membranes obtained with the increase of Eu-TiO2 NPs content during the preparation process were named M1, M2 and M3, respectively. The pure PVDF membrane without the addition of Eu-TiO2 NPs was named M0, which was prepared by the immersion phase inversion method and served as a reference. The prepared Eu-TiO2/PVDF membranes could not only adsorb MO, but also degrade CIP under visible-light irradiation. Moreover, the Eu-TiO2/PVDF membranes exhibited adsorption-photocatalytic activity towards a mixture of MO and CIP under visible-light irradiation. Last but not the least, the Eu-TiO2/PVDF membranes exhibited excellent recyclability and reusability, opening the avenue for a possible use of these membranes in sewage-treatment plants.

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1-150 µM and 10-150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications

From scientific and technological points of view, poly(vinylidene fluoride), PVDF, is one of the most exciting polymers due to its overall physicochemical characteristics. This polymer can crystalize into five crystalline phases and can be processed in the form of films, fibers, membranes, and specific microstructures, being the physical properties controllable over a wide range through appropriate chemical modifications. Moreover, PVDF-based materials are characterized by excellent chemical, mechanical, thermal, and radiation resistance, and for their outstanding electroactive properties, including high dielectric, piezoelectric, pyroelectric, and ferroelectric response, being the best among polymer systems and thus noteworthy for an increasing number of technologies. This review summarizes and critically discusses the latest advances in PVDF and its copolymers, composites, and blends, including their main characteristics and processability, together with their tailorability and implementation in areas including sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidic, tissue engineering, and antimicrobial applications. The main conclusions, challenges and future trends concerning materials and application areas are also presented.

Modification of Carbon Dots for Metal‐Ions Detection

It is very appealing to develop cheap, highly sensitive and efficient metal ion fluorescence sensors as traditional instrument methods are inherently costly and time‐consuming. Carbon dots (CDs) are widely used for sensing metal ions, attributing to their merits of good biocompatibility, low toxicity, easy surface modification and excellent photostability. This article reviewed the research progress of CDs as metal ion sensors in recent years, and studied their modification methods and detection performances. Finally, the challenges and opportunities of CDs as metal ion sensors were also analyzed. This article is expected to provide inspiration and help for researchers focusing on CDs as metal ion sensors.

Biosorption kinetics of cerium(III) and cobalt(II) from liquid wastes using individual bacterial species isolated from low-level liquid radioactive wastes

The existence of toxic heavy metals in the aquatic environment has emphasized a considerable exigency to develop several multifunctional biosorbents for their removal. Herein, three individual bacterial species of Cellulosimicrobium cellulans, Bacillus coagulans, and Microbacterium testaceum were successfully isolated from low-level liquid radioactive wastes. Their loading capacities towards cerium and cobalt metal ions were inclusivity inspected under variable operational parameters of pH, primary pollutant concentration, interaction time, temperature, stirring speed, and biosorbent dosage. By analyzing the influence of solution pH, concentration, temperature, biosorbent mass, and agitation speed on the biosorption kinetics, the biosorption process confirms pseudo-second-order kinetic, intraparticle diffusion, and Elovich equation. Remarkably, the isolated Microbacterium testaceum exhibited high loading capacities reaching 68.1 mg g^-1, and 49.6 mg g^-1 towards Ce(III), and Co(II) ions, respectively, at the initial concentration of 2.8 mM, pH 4.5, and 25 °C. Overall, the isolated bacterial species can potentially be offered up as a promising scavenger for Ce(III) and Co(II) from liquid waste effluents.

Improvement of Photocatalytic Performance by Building Multiple Heterojunction Structures of Anatase-Rutile/BiOI Composite Fibers

In this study, multiple heterojunction structures of anatase-rutile/Bismuth oxyiodide (BiOI) composite fibers are designed by the combined method of electrospinning and hydrothermal techniques. The influence of different Ti/Bi atomic ratios ([Ti/Bi]) on the nanostructures and photocatalytic properties are investigated. It is found that the morphology of BiOI covered on the TiO₂ fiber surface changed with [Ti/Bi] from nanosheets to submicron spheres structures. Additionally, the crystallization of the composite fibers including the phases of anatase, rutile, and BiOI is identified, theses phases are in close contact with each other, and the interfacial effects are helpful to form the multiple heterojunctions which lead to blue shifts on the chemical state of Ti. The absorption of visible light has been improved by compositing BiOI on TiO₂, while the band gap values of the composite fibers are significantly reduced, which can enhance the generation and separation of electrons and holes. For the case of [Ti/Bi] = 1.57, the photodegradation rate of anatase-rutile/BiOI composite fibers is about 12 times that of pure TiO₂. For the photocatalytic mechanism, the synergistic s-type heterojunctions increase the content of active oxides which have a positive effect on the degradation rate.