Effect of an external magnetic field applied in batch adsorption systems: Removal of dyes and heavy metals in binary solutions

Solid waste collagen-associated fabrication of magnetic hematite nanoparticle@collagen nanobiocomposite for emission-adsorption of dyes

The strategic utilization of hazardous particulate waste in eliminating environmental pollution is an important research hotspot. Herein, abundantly available hazardous solid collagenic waste of leather industry is converted into stable hybrid nanobiocomposite (HNP@SWDC) comprising magnetic hematite nanoparticles (HNP) and solid waste derived collagen (SWDC) via co-precipitation method. The structural, spectroscopic, surface, thermal, and magnetic properties; fluorescence quenching; dye selectivity; and adsorption are explored via microstructural analyzes of HNP@SWDC and dye adsorbed-HNP@SWDC using ¹H nuclear magnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared (FTIR), X-ray photoelectron, and fluorescence spectroscopies; thermogravimetry; field-emission scanning electron microscopy; and vibrating-sample magnetometry (VSM). The intimate interaction of SWDC with HNP and elevated magnetic properties of HNP@SWDC are apprehended via amide-imidol tautomerism associated nonconventional hydrogen bondings, disappearance of goethite specific -OH def. in HNP@SWDC, and VSM. The as-fabricated reusable HNP@SWDC is employed for removing methylene blue (MB) and rhodamine B (RhB). Chemisorption of RhB/MB in HNP@SWDC via ionic, electrostatic, and hydrogen bonding interactions alongside dimerization of dyes are realized by ultraviolet-visible, FTIR, and fluorescence studies; pseudosecond order fitting; and activation energies. The adsorption capacity = 46.98-56.14/22.89-27.57 mg g^-1 for RhB/MB is noted using 0.01 g HNP@SWDC within 5-20 ppm dyes and 288-318 K.

Removal of metal ions using a new magnetic chitosan nano-bio-adsorbent; A powerful approach in water treatment

In this study, a magnetic chitosan/Al₂O₃/Fe₃O₄ (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.

Electro/magnetic superposition effects on diclofenac degradation: Removal performance, kinetics, community structure and synergistic mechanism

Electric and magnetic fields characterized by high efficiency, low consumption and environment-friendly performance have recently generated interest as a possible measure to enhance the performance of the biological treatment process used to remove refractory organics. Few studies have been carried out to-date regarding the simultaneous application of electric and magnetic fields on biofilm process to degrade diclofenac. In this study, 3DEM-BAF was designed to evaluate the electrio-magnetic superposition effect on diclofenac removal performance, kinetics, community structure and synergistic mechanism. The results show that 3DEM-BAF could significantly increase the average removal rate of diclofenac by 65.30 %, 57.46 %, 9.48 % as compared with that of BAF, 3DM-BAF, 3DE-BAF, respectively. The diclofenac degradation kinetic constants and dehydrogenase activity of 3DEM-BAF were almost 6.72 and 2.53 times higher than those of BAF. Microorganisms of 3DEM-BAF in the Methylophilus and Methyloversatilis genera were distinctively enriched, which was attributed to the screening function of electric field and propagation effect of magnetic field. Moreover, three processes were found to contribute to diclofenac degradation, namely electro-magnetic-adsorption, electro-chemical oxidation and electro-magnetic-biodegradation. Thus, the simultaneous application of electric and magnetic fields on biofilm process was demonstrated to be a promising technique as well as a viable alternative in diclofenac degradation enhancement.

Simultaneous adsorptive removal of conventional and emerging contaminants in multi-component systems for wastewater remediation: A critical review

The rapid growth of population and industrialization results in pollution of freshwater sources which leads to the water stress conditions on the world in future. Adsorption is a low cost and popular technique for the removal of contaminants from water bodies. Most of the reports till date are on removal of a single component from aqueous solutions using this technique, but the real-world effluent contains multiple contaminants such as dyes, heavy metals, pesticides, antibiotics and many more. Therefore, a study on simultaneous removal of contaminants is highly needed to obtain a suitable adsorbent that can be used commercially. This critical review provides a detailed study on the removal of contaminants in the presence of other contaminant/s i.e., from a multi-component system (MCS). The different possible interaction mechanisms in MCS like synergism, antagonism and non-interaction are discussed. The MCS containing the mixture of conventional contaminants such as heavy metals and dyes, and other emerging contaminants such as antibiotics, organic contaminants, pesticides and personal care products are explained in depth. This review article will be helpful for researchers working in the field of simultaneous removal of contaminants from MCSs for wastewater remediation.

Magnetic nanoadsorbents for micropollutant removal in real water treatment: a review

Pure water will become a golden resource in the context of the rising pollution, climate change and the recycling economy, calling for advanced purification methods such as the use of nanostructured adsorbents. However, coming up with an ideal nanoadsorbent for micropollutant removal is a real challenge because nanoadsorbents, which demonstrate very good performances at laboratory scale, do not necessarily have suitable properties in in full-scale water purification and wastewater treatment systems. Here, magnetic nanoadsorbents appear promising because they can be easily separated from the slurry phase into a denser sludge phase by applying a magnetic field. Yet, there are only few examples of large-scale use of magnetic adsorbents for water purification and wastewater treatment. Here, we review magnetic nanoadsorbents for the removal of micropollutants, and we explain the integration of magnetic separation in the existing treatment plants. We found that the use of magnetic nanoadsorbents is an effective option in water treatment, but lacks maturity in full-scale water treatment facilities. The concentrations of magnetic nanoadsorbents in final effluents can be controlled by using magnetic separation, thus minimizing the ecotoxicicological impact. Academia and the water industry should better collaborate to integrate magnetic separation in full-scale water purification and wastewater treatment plants.

An Environmentally Friendly Method for Removing Hg(II), Pb(II), Cd(II) and Sn(II) Heavy Metals from Wastewater Using Novel Metal–Carbon-Based Composites

Rapid economic and industrial development and population growth have made water contamination a serious environmental problem and a major threat to public health worldwide. Heavy metals are extensively used in numerous industrial applications and are some of the most important environmental contaminants. The impacts of heavy metals on the health of humans, animals, and plants make their removal from wastewater and water resources an important and vital issue. In this study, a simple and environmentally friendly method is proposed for the synthesis of a ZnFe2O4-carbon nanotube (CNT) adsorbent material. SEM/EDX analysis and Fourier-transform infrared spectrophotometry (FTIR) are used to characterize the synthesized adsorbent material. We test the synthesized adsorbent material’s ability to recover four heavy metals (Hg(II), Pb(II), Cd(II) and Sn(II) ions) from an aqueous solution. We show that crushing fullerene CNTs with the ZnFe2O4 composite improves the adsorption properties of free fullerene CNTs towards the investigated heavy metal ions by 25%.

Application of magnetic fields to wastewater treatment and its mechanisms: A review

Magnetic field (MF) has been applied widely and successfully as an efficient, low-cost and easy-to-use technique to enhance wastewater treatment (WWT) performance. Although the effects of MF on WWT were revealed and summarized by some works, they are still mysterious and complex. This review summarizes the application of MF in magnetic adsorption-separation of heavy metals and dyes, treatment of domestic wastewater and photo-magnetic coupling technology. Furthermore, the mechanisms of MF-enhanced WWT are critically elaborated from the perspective of magnetic physicochemical and biological effects, such as magnetoresistance, Lorentz force, and intracellular radical pair mechanism. At last, the challenges and opportunities for MF application in WWT are discussed. For overcoming the limitations and taking advantages of MFs in WWT, fundamental research of the mechanisms of the application of MFs should be carried out in the future.

Sustainable Adsorption Removal of Nickel and Chromium on Eco-Friendly Industrial Waste: Equilibrium Study

Adsorption of nickel and chromium was investigated using fuller’s earth. The experimental data were analyzed using five 2-parameter adsorption models and three 3-parameter models. The maximum adsorption capacities for nickel and chromium were 769 and 556 mg/g, respectively. The Langmuir isotherm model was found to have the best fitting indicating monolayer adsorption. The adsorption was found to have an exothermic nature.

Fabrication of novel amine-functionalized magnetic silica nanoparticles for toxic metals: kinetic and isotherm modeling

In this research, an amine-functionalized magnetic silica nanosorbent was prepared using the co-precipitation technique, and this nanosorbent can be effortlessly detached using an external magnetic field. FTIR and SEM analyses identified that the nanosorbent holds extraordinary adsorption characteristics for toxic metals' (copper, cadmium, zinc, and nickel) removal. The adsorption-affecting parameters were optimized, and the thermodynamic studies assessed that the adsorption process seemed to be spontaneous, feasible, and exothermic. The pseudo-first-order and Freundlich models perfectly fit the kinetic and equilibrium data, respectively. Langmuir monolayer capacity of the nanosorbent was analyzed using nonlinear evaluation methods such as 419.9 mg/g for copper, 321.9 mg/g for nickel, 217.3 mg/g for cadmium, and 137.6 mg/g for zinc. The used adsorbent was simply rejuvenated using the 0.2 N HCl solution subsequently with intense agitation. The result of the present research confirms that the produced nanosorbent can be effectively utilized for industrial wastewater management.

Effects of electromagnetic induction on migration and speciation of heavy metals in drying sewage sludge: Mechanistic insights

Novel and efficient drying method based on electromagnetic induction plate (EMI-P) heating was used to treat sewage sludge (SS). This work focused on the effects of EMI-P action on heavy metals (HMs) in dried SS. Surface functional groups, surface chemistry and microstructures of SS treated were investigated and compared to provide insights into the transformation mechanisms of HMs during EMI-P drying process. The results show that the EMI-P-dried SS showed undesirably total concentrations of Cd and Zn and leaching concentrations of HMs (Cr, Ni, Zn, Cd and As) exceeded the Chinese ground water standard (GB/T14848-2017). Ni, Zn, and As in the EMI-P-dried SS still exhibited high mobility, the leaching percent of Ni, Zn, and As (under 300 V and 500 V) can reach up to 28.56%/10.36%, 26.96%/26.61% and 30.64%/23.14%, respectively. Compared with conventional thermal drying, the EMI-P method can effectively reduce the eco-toxicity derived from HMs by 28.06% under 500 V condition. The stabilization effect of the EMI-P action can be attributed to the following: (1) EMI-P action promoted the generation of surface complexes with HMs, (2) HMs adsorption by silicate minerals was enhanced under high-frequency magnetic fields and (3) honeycomb structures of EMI-P dried SS with micropores provided abundant active sites to bond with HMs.

Simultaneous removal of methylene blue and Pb2+ from aqueous solution by adsorption on facile modified lignosulfonate

In this paper, simultaneous removal of methylene blue (MB) and Pb²⁺ from the binary component system by an easily prepared cross-linked lignosulfonate bio-adsorbent (CLLS) was described. CLLS was characterized by FTIR, SEM/EDS and TGA. The influences of pH, temperature, contact time and initial MB and Pb²⁺ concentrations on the adsorption performance were investigated. The results demonstrated a good ability of CLLS to remove MB and Pb²⁺ simultaneously. Using of 1.0 g L^-1 loading, removal efficiency of MB and Pb²⁺ reached 98.0% and 97.8%, respectively, in the MB (100 mg.L^-1)-Pb²⁺ (50 mg.L^-1) system. Moreover, the adsorption isotherms and adsorption kinetics indicated that the results were fitting well with the Langmuir and pseudo-second-order model, respectively, for both MB and Pb²⁺. Based on the Langmuir model, the maximum adsorption capacity of MB and Pb²⁺ reached 132.6 and 64.9 mg g^-1, respectively, in the MB-Pb²⁺ system, which was much lower than that in the single component system (358.4 mg g^-1 100.9 mg g^-1 for MB and Pb²⁺, respectively). Hence, simultaneous adsorption of MB and Pb²⁺ onto CLLS was an antagonistic adsorption. In addition, an apart-sequential adsorption method was used to study the action of adsorption sites on CLLS for MB and/or Pb²⁺ with the help of an efficient self-made apparatus. Rudimental results showed that there would be three different kinds of adsorption sites on CLLS: MB-site, Pb²⁺-site and MB/Pb²⁺- shared sites. Furthermore, in the MB (100 mg.L^-1)-Pb²⁺(50.0 mg.L^-1) system, the simultaneous removal efficiency of MB and Pb²⁺ still maintained 91.8% and 85.0%, respectively, after 6 cycles.