Removal of hexavalent chromium from water using polyaniline/ wood sawdust/ poly ethylene glycol composite: an experimental study

Synthesis of gamma irradiated acrylic acid-grafted-sawdust (SD-g-AAc) for trivalent chromium adsorption from aqueous solution

Water pollution caused by chromium released from tannery is a serious concern to the environment and public health. Chromium removal from tannery effluent is a crying need before discharging to the surface water. In this study, acrylic acid-grafted sawdust was prepared by Tectona grandis sawdust grafting with acrylic acid employing gamma irradiation in the presence of air and Mohr's salt. It was treated with NaOH and the characterization of surface morphology and functional groups of modified sawdust was studied by SEM and FTIR.. The effects of solution pH, adsorbent dosage, adsorption time, and initial Cr(III) ion concentration were investigated by batch sorption studies. The process was found to be pH, temperature and concentration dependent. Langmuir and Freundlich isotherms were applied to realize the adsorption process in depth, and it was found that the Langmuir isotherm model fitted well with experimental data (R2 value of 0.983). The maximum monolayer adsorption capacity of acrylic acid-grafted sawdust for Cr(III) from aquous solution was found to be 21.55 mg g-1 at 25 °C. Pseudo-first-order and pseudo-second-order kinetic models were employed to analyze the kinetics of the process, and it was found that the experimental process followed the pseudo-second-order kinetic model, i.e. chemisorption. This study revealed that acrylic acid-grafted sawdust has a decent potential for the removal of Cr(III) from tannery effluents.

Synthesis and characterization of PANI-ZrWPO4 nanocomposite: adsorption-reduction efficiency and regeneration potential for Cr(VI) removal

A novel polyaniline zirconium tungstophosphate (PANI-ZrWPO4) nanocomposite was successfully synthesized through an in situ oxidative polymerization reaction followed by a microwave irradiation process. The synthesized nanocomposite was characterized by using FESEM, EDX, TEM, XRD, FTIR, Raman, TGA-DTA, XPS, and N2 adsorption-desorption analysis and chemical analysis to know about the formation of material. The results of the FTIR and Raman spectra confirmed that the conducting PANI polymer interacted with ZrWPO4 to form the PANI-ZrWPO4 nanocomposite. The XRD data showed that the composite had a crystalline nature. The TEM and FESEM images revealed that polyaniline had formed on the exterior of the PANI-ZrWPO4 nanocomposite. Further investigation was done on the efficiency of the PANI-ZrWPO4 nanocomposite as an adsorbent for Cr(VI) removal through batch adsorption experiments. The maximum Langmuir adsorption capacity of PANI-ZrWPO4 was found to be 71.4 mg g-1. The removal of Cr(VI) was optimized with the six variables namely adsorbent dose, initial concentration, Time, pH, Temperature, and stirring rate using the Box-Behnken design (BBD) model. The XPS spectra confirmed simultaneously adsorption reduction occurs Cr(VI) to Cr(III) through in situ chemical reduction. Moreover, the regeneration efficiency of PANI-ZrWPO4 was studied, and it was found to be able to remove around 80% of Cr(VI) even after five cycles, demonstrating its potential as an effective and reusable adsorbent.

Fabrication of Polyamide6/Polyaniline as an Effective Nano-web Membrane for Removal of Cr (VI) from Water and a Black Box Approach in Modeling of Adsorption Process

Chromium (Cr), as a highly toxic heavy metal ion, is still a severe environmental issue, although many research efforts have been put into its removal from water. Polyaniline (PANI), as a conductive polymer, demonstrated great capability in heavy metal adsorption due to its low cost, ease of synthesis, reversible redox behavior, and chemical stability. However, using PANI powder alone in heavy metal removal causes secondary pollution and aggregation in water. The PANI coating on a substrate could tackle this problem. In this study, polyaniline-coated polyamide6 (PA6/PANI) nano-web membrane was used for the removal of Cr(VI) in both adsorption and filtration-adsorption modes. The PA6/PANI nano-web membrane was fabricated via PA6 electrospinning followed by in-situ polymerization of the aniline monomer. The electrospinning condition of PA6 was optimized by the Taguchi method. The PA6/PANI nano-web membrane was characterized by FESEM, N2-adsorption/desorption, FT-IR, contact angle measurement, and tensile test. FT-IR and FESEM results demonstrated the successful synthesis of PA6/PANI nano-web and PANI homogeneous coating on PA6 nanofibers, respectively. The N2 adsorption/desorption results indicated that the pore volume of the PA6/PANI nano-web decreased by 39% compared to PA6 nanofibers. The tensile test and water contact angle studies showed that the coating of PANI on PA6 nanofibers improves the mechanical properties and hydrophilicity of PA6 by 10% and 25%, respectively. The application of PA6/PANI nano-web in the removal of Cr(VI) in batch and filtration modes exhibits excellent removal of 98.4 and 86.7%, respectively. A pseudo first order model well described the adsorption kinetics, and the adsorption isotherm was best fitted by the Langmuir model. A black box modeling approach based on artificial neural networks (ANN) was developed to predict the removal efficiency of the membrane. The superior performance of PA6/PANI in both adsorption and filtration-adsorption systems makes it a potential candidate for the removal of heavy metals from water on an industrial scale.

Characterization and synthesis of new adsorbents with some natural waste materials for the purification of aqueous solutions

In this study, hexavalent chromium Removal from aqueous environments was investigated by using polyaniline composites with some natural waste materials. Batch experiments were used, and some parameters such as contact time, pH and adsorption isotherms were determined for the best composite with the highest removal efficiency. Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) were used to characterize the composites. According to the results, the polyaniline/walnut shell charcoal/PEG composite outperformed other composites and showed the highest chromium removal efficiency of 79.22%. Polyaniline/walnut shell charcoal/PEG has a larger specific surface area of 9.291 (m²/gr) which leads to an increase in its removal efficiency. For this composite, the highest removal efficiency was obtained at the pH = 2 and 30 min contact time. The maximum calculated adsorption capacity was 500 mg/g.

A review of novel green adsorbents as a sustainable alternative for the remediation of chromium (VI) from water environments

The presence of heavy metal, chromium (VI), in water environments leads to various diseases in humans, such as cancer, lung tumors, and allergies. This review comparatively examines the use of several adsorbents, such as biosorbents, activated carbon, nanocomposites, and polyaniline (PANI), in terms of the operational parameters (initial chromium (VI) concentration (C_o), temperature (T), pH, contact time (t), and adsorbent dosage) to achieve the Langmuir's maximum adsorption capacity (q_m) for chromium (VI) adsorption. The study finds that the use of biosorbents (fruit bio-composite, fungus, leave, and oak bark char), activated carbons (HCl-treated dry fruit waste, polyethyleneimine (PEI) and potassium hydroxide (KOH) PEI-KOH alkali-treated rice waste-derived biochar, and KOH/hydrochloric acid (HCl) acid/base-treated commercial), iron-based nanocomposites, magnetic manganese-multiwalled carbon nanotubes nanocomposites, copper-based nanocomposites, graphene oxide functionalized amino acid, and PANI functionalized transition metal are effective in achieving high Langmuir's maximum adsorption capacity (q_m) for chromium (VI) adsorption, and that operational parameters such as initial concentration, temperature, pH, contact time, and adsorbent dosage significantly affect the Langmuir's maximum adsorption capacity (q_m). Magnetic graphene oxide functionalized amino acid showed the highest experimental and pseudo-second-order kinetic model equilibrium adsorption capacities. The iron oxide functionalized calcium carbonate (IO@CaCO₃) nanocomposites showed the highest heterogeneous adsorption capacity. Additionally, Syzygium cumini bark biosorbent is highly effective in treating tannery industrial wastewater with high levels of chromium (VI).

Efficient adsorption of hexavalent chromium ions onto novel ferrochrome slag/polyaniline nanocomposite: ANN modeling, isotherms, kinetics, and thermodynamic studies

The current research is concerned with the adsorption behavior of chromium (IV) ions in an aqueous solution using a novel ferrochrome slag/polyaniline nanocomposite (FeCr-PANI) adsorbent. The effect of process parameters such as temperature, pH solution, initial Cr (VI) ions concentration, adsorbent dosage, and contact time on the adsorption process is experimentally investigated in this study. Furthermore, we have trained a multilayer artificial neural network (ANN) using the experimental data of various process parameters to successfully predict the adsorption behavior of chromium (IV) ions onto the FeCr-PANI adsorbent. The ANN model was trained using the Lavenberg-Marquardt algorithm and ten neurons in the hidden layer and was able to estimate the % removal efficiency of chromium (IV) under the influence of different process parameters (R² = 0.991). Initial solution pH was observed to have a significant influence on the % removal efficiency. The % removal efficiency was found to be high at 97.10% for the solution with pH 3 but decreased to 64.40% for the solution with pH 11. Cr (VI) % removal efficiency was observed to increase with an increase in solution temperature, adsorbent dosage, and contact time. However, the % removal efficiency was found to decrease from 96.9 to 54.8% with increasing the initial dye concentration from 100 to 400 ppm. Furthermore, the adsorption capacity increased from 9.69 to 21.93 mg/g with an increase in the initial concentration from 100 to 400 ppm, as expected. The Langmuir isotherm model exhibited the best fit with the experimental data (R² = 0.9977). The maximum adsorption capacity was found to be 22.523 mg g^-1 at 298 K. The experimental data fitted well with the pseudo-second-order kinetic model.

Investigating the hexavalent chromium removal from aqueous solution applying bee carcasses and corpses modified with Polyaniline

There are currently heavy metals in most industrial effluents which are among the most significant environmental pollutants. Hexavalent chromium is one of the most significant heavy metals. In this research for the first time, eliminating the hexavalent chromium from the aqueous medium/aquedia applying bee carcasses and corpses modified with polyethylene was examined. Adsorption experiments were conducted discontinuously on laboratory solutions, including hexavalent chromium. The optimal adsorption conditions such as different pH factors, contact time, initial chromium concentration, and adsorbent value on the adsorption rate were examined at different levels, and adsorption isotherms were plotted. Some adsorbent properties were examined using Field Emission Scanning Electron Microscopy, XRD analysis, Fourier Transform Infrared Spectroscopy, and BET test to study the properties of the synthesized adsorbent. This study indicated that the highest percentage of removal related to polyethylene composite and bee carcasses in the presence of polyethylene glycol was 50.56% among the bee carcasses composites. The parameters effective on the adsorption process for polyethylene composite and bee carcasses and losses in the presence of polyethylene glycol suggested that the adsorption percentage increased for this composite by decreasing the pH, increasing the contact time, and increasing the adsorbent. The highest percentage of adsorption was obtained when the pH was 2, the contact time was 120 min and the adsorbent value was 8 g/L and the initial concentration of chromium was 100 ppm. The most optimal removal percentage was achieved at the pH = 2, the contact time was 30 min, and the adsorbent value was 2 g/L, and the initial chromium concentration was 100 ppm. The results of drawing adsorption isotherms also indicated that higher R2 had a better fit than Langmuir for polyethylene composite and bee carcasses in the polyethylene glycol Freundlich equation.

Sawdust, a versatile, inexpensive, readily available bio-waste: From mother earth to valuable materials for sustainable remediation technologies

Sawdust or wood shaving is a relatively abundant and inexpensive lignocellulosic compound, which is provided by mother nature. It is a waste of industry and agriculture, that is found in large quantities and has disposal problems. Nowadays, waste management (like sawdust) and research on converting it to different compounds for special applications and goals have been receiving tremendous attention. So, introducing sawdust as a kind of interesting bio-waste and turn it into wealth for diverse utilizations can be mentioned as the main goal of this overview. In this regard, in the first part, sawdust structure and properties are considered. It is then followed by highlighting its wide applications in sustainable water remediation technology, production of activated carbon, oil-water separation, and high-performance composites fabrication. Please come on to start a journey on this motivating topic.

Three-dimensional (3D) polymer-metal-carbon framework for efficient removal of chemical and biological contaminants

The continuously increased existence of contaminants such as chemical and biological mainly dye, bacteria, and heavy metals ions (HMI) in water bodies has increased environmental concern due to their hostile effects on living things. Therefore, there is necessity to be developed newer materials that skirmishes such environmental menace. The present works focus on the synthesis of a novel three-dimensional (3D) polymer-metal-carbon (3D-PMC) framework for the exclusion of contaminants (chemical and biological) from water bodies. Initially, polyurethane (PU) foam was treated with nitric acid and used as a framework for the development of 3D-PMC materials. The copper nanosheet (Cu-NS) was deposited onto the functionalized PU foam to produce Cu-NS-PU material. The mechanically exfoliated graphene was mixed with chitosan to produce a graphene-chitosan homogenous suspension. The produce homogenous suspension was deposited Cu-NS-PU for the development of the 3D-PMC framework. The prepared 3D-PMC framework was characterized by scanning electron microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), Fourier-transform infrared spectroscopy (FT-IR), and X-rays diffraction (XRD) analysis. The prepared 3D-PMC framework was subjected to various adsorption parameters to assess the sorption ability of the material. The prepared 3D-PMC framework was effectively used for the removal of chromium (Cr) metal ions and Congo-red (CR) dye from the water system. The synthesis of the 3D-PMC framework is simple, novel, cost-effective, and economically viable. Therefore, the prepared 3D-PMC framework has the potential to be used as a filter assembly in water treatment technologies.

Comparison of effects of nanofluid utilization (Al2O3, SiO2, TiO2) with reference water in automotive radiators on exergetic properties of diesel engines

In this study, nanofluids formed by using ethylene glycol and three kinds of nanoparticles such as Al2O3, SiO2, and TiO2 were added to the four-stroke internal combustion engine radiator and compared with the conventional coolant (pure water). This comparison is based on the exergy performances which are the main theme of the second law of thermodynamics. The tests were carried out at a fixed engine speed of 1800 rpm using diesel fuel, and the outputs were obtained from the test setup experimentally. A total of six nanofluid tests were performed on two different dispersions (0.2% and 0.4%). As a result of this study, the best exergy efficiency was obtained by using TiO2 particles with a 35.67% value. Increasing the percentage of nanoparticles in the fluid from 0.2 to 0.4 positively affected efficiency. Pure water generally lagged behind nanofluid performance in experimental parameters. Compared to conventional coolant (pure water), the lowest exhaust temperature value was measured by using an Al2O3/Ethylene Glycol mixture with a difference of 59 K. Also, by using Al2O3 nanoparticles as a coolant, 8.858 kW of exergy exhaust value was obtained. This is the best emission value measured in the experimental study. While calculating values close to each other in the use of other nanoparticles, the worst exergy exhaust results were obtained by using the conventional refrigerant. Consequently, in this paper, exergetic outputs such as exergetic efficiency, exergy destruction, exergy heat, exergy work, exergy total exhaust, and entropy production rate were calculated for pure water and each nanofluid.

Removal of heavy metals and radionuclides from water using nanomaterials: current scenario and future prospects

There is an increase in concern about the hazardous effects of radioactivity due to the presence of undesirable radioactive substances in our vicinity. Nuclear accidents such as Chernobyl (1986) and Fukushima (2011) have further raised concerns towards such incidents which have led to contamination of water bodies. Conventional methods of water purification are less efficient in decontamination of radioisotopes. They are usually neither cost-effective nor environmentally friendly. However, nanotechnology can play a vital role in providing practical solutions to this problem. Nano-engineered materials like metal oxides, metallic organic frameworks, and nanoparticle-impregnated membranes have proven to be highly efficient in treating contaminated water. Their unique characteristics such as high adsorption capacity, large specific surface area, high tensile strength, and excellent biocompatibility properties make them useful in the field of water purification. This review explores the present status and future prospects of nanomaterials as the next-generation water purification systems that can play an important role in the removal of heavy metals and radioactive contaminants from aqueous solutions.

Numerical treatment of radiative Nickel-Zinc ferrite-Ethylene glycol nanofluid flow past a curved surface with thermal stratification and slip conditions

The inadequate cooling capacity of the customary fluids forced the scientists to look for some alternatives that could fulfill the industry requirements. The inception of nanofluids has revolutionized the modern industry-oriented finished products. Nanofluids are the amalgamation of metallic nanoparticles and the usual fluids that possess a high heat transfer rate. Thus, meeting the cooling requirements of the engineering and industrial processes. Having such amazing traits of nanofluids in mind our aim here is to discuss the flow of nanofluid comprising Nickel–Zinc Ferrite and Ethylene glycol over a curved surface with heat transfer analysis. The heat equation contains nonlinear thermal radiation and heat generation/absorption effects. The envisioned mathematical model is supported by the slip and the thermal stratification boundary conditions. Apposite transformations are betrothed to obtain the system of ordinary differential equations from the governing system in curvilinear coordinates. A numerical solution is found by applying MATLAB build-in function bvp4c. The authentication of the proposed model is substantiated by comparing the results with published articles in limiting case. An excellent concurrence is seen in this case. The impacts of numerous physical parameters on Skin friction and Nusselt number and, on velocity and temperature are shown graphically. It is observed that heat generation/absorption has a significant impact on the heat transfer rate. It is also comprehended that velocity and temperature distributions have varied behaviors near and far away from the curve when the curvature is enhanced.

Elaboration of novel polyaniline@Almond shell biocomposite for effective removal of hexavalent chromium ions and Orange G dye from aqueous solutions

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g^-1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Magnetic magnesium ferrite-doped multi-walled carbon nanotubes: an advanced treatment of chromium-containing wastewater

Magnetic magnesium ferrite (MgFe₂O₄) nanoparticles (MMFNPs) were synthesized by employing the sol-gel method. These nanoparticles were ultrasonically decorated onto the multi-walled carbon nanotubes (MWCNTs) to produce magnetic magnesium ferrite nanocomposites (MMFNCs). The as-prepared materials were investigated for their capability to treat wastewater loaded with heavy metals. The synthesized nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transmission infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and zeta analyzer. Besides, the effect of the environmental chemistry of the solution was determined by varying the critical parameters. The adsorption isotherm of Cr(VI) adsorption onto the as-synthesized MMFNC best fitted the Langmuir adsorption isotherm model. The high adsorption capacity of 175.43 mg/g was achieved at a temperature of 40 °C under optimized conditions. Due to the magnetic nature of MMFNC, they are easily recoverable from the aqueous solution making them cost-friendly. Even after seven consecutive adsorption-desorption cycles, the MMFNC presented an efficiency loss of less than 20% for the removal of Cr(VI) ions. The presented development method offers prospects in developing a highly effective magnetic adsorbent for heavy metal removal from wastewater.

The development of a ternary nanocomposite for the removal of Cr(vi) ions from aqueous solutions

The aim of this study is to develop a ternary nanocomposite (NC) of polyaniline (PANI)/2-acrylamido-2-methylpropanesulfonic acid (AMPSA)-capped silver nanoparticles (NPs)/graphene oxide quantum dots (PANI/Ag (AMPSA)/GO QDs) as an efficient adsorbent for the removal of the highly toxic hexavalent chromium (Cr(vi)) from polluted water. PANI/Ag (AMPSA)/GO QDs NC was synthesized via in situ oxidative polymerization. The effects of pH, adsorbent dose, initial concentration, temperature, contact time, ionic strength and co-existing ions on the removal of Cr(vi) by PANI/Ag (AMPSA)/GO QDs were investigated. The PANI/Ag (AMPSA)/GO QDs NC (25.0 mg) removed 99.9% of Cr(vi) from an aqueous solution containing 60 mg L⁻¹ Cr(vi) ions at pH 2. Energy dispersive X-ray (EDX) and inductively coupled plasma spectrometry (ICP) studies confirmed the adsorption of Cr(vi) and that some of the adsorbed Cr(vi) was reduced to Cr(iii). Cr(vi) removal by the PANI/Ag (AMPSA)/GO QDs NC followed the pseudo-second order kinetic model, and the removal was highly selective for Cr(vi) in the presence of other co-existing ions. In summary, the PANI/Ag (AMPSA)/GO QDs NC has potential as a novel adsorbent for Cr(vi).

The aim is to develop a ternary nanocomposite of polyaniline/2-acrylamido-2-methylpropanesulfonic acid-capped silver nanoparticles/graphene oxide quantum dots as an efficient adsorbent for the removal of the highly toxic hexavalent chromium (Cr(vi)) from polluted water.