Search Results (5)

The shear flow instabilities under the presence of magnetic fields in the primordial disk can greatly facilitate the formation of density structures that serve as seeds prior to the onset of the gravitational Jeans instability. We evaluate the effects of the Parker, magnetorotational and kinematic dynamo instabilities by comparing the properties of these instabilities. We calculate the mass spectra of coagulated density structures by the above mechanism in the radial direction for an axisymmetric magnetohydrodynamic (MHD) torus equilibrium and power density profile models. Our local three-dimensional MHD simulation indicates that the coupling of the Parker and magnetorotational instability creates spiral arms and gas blobs in an accretion disk, reinforcing the theory and model. Such a mechanism for the early structure formation may be tested in a laboratory. The recent progress in experiments involving shear flows in rotating tokamak, field reversed configuration (FRC) and laser plasmas may become a key element to advance in nonlinear studies. Full article

The efficiency of magnetic seed coagulation (MSC) with pH adjustment by NaOH and Ca(OH)₂ as a pretreatment for high-strength natural rubber industrial wastewater (NRIWW) was compared in this study. The high content of suspended solids (SSs) and other inhibitory substances of NRIWW is a primary issue which affects its subsequent secondary and tertiary treatment processes. The MSC process with polyaluminum chloride (PAC), anionic polymer (polyacrylamide—PAM)), and magnetic seeds (MS) (ferric oxide (Fe₃O₄)) was proven to be a cost-effective pretreatment of NRIWW, and Ca(OH)₂ showed improved pretreatment performance, with turbidity, COD, and TSS removals of 95%, 56%, and 64%, respectively. Sedimentation was enhanced from 30 min by conventional coagulation to less than 5 min by the MSC. The organic components of NRIWW reacted with MS to generate Fe–OH/Fe–OH⁺ linkages through processes of surface complexing and hydrogen bonding. According to fractal analysis, the MSC process optimized with Ca(OH)₂ produces less complex flocs that are uniform and densely packed. Additionally, MS served as an adsorbent and promoted the development of magnetic flocs by boosting their density and size. MSC with pH adjustment by Ca(OH)₂ presents a robust and cost-effective pretreatment process for NRIWW. Full article

Green water treatment technologies are widely popular, and magnetic coagulation is one of the most popular methods and has been successfully applied in industry. Among them, magnetic seeds are crucial for the flocculation of contaminants. The objective of this work was to investigate the potential of magnetic metal–organic frameworks (MMOFs) as a seed in assisting polymeric ferric sulfate (PFS) flocculant, specifically exploring their applicability in algal-contaminated water. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, ferrite timing spectroscopy, and flocculation tests were used to characterize the structure and flocculation properties of MMOFs and PFS (PFS-MMOFs) composites, highlighting the stability of magnetic seed MMOFs and the flocculation effect of the composites. The results show that MMOFs have good dispersion and stability in acidic PFS solutions, which are favorable for engineering applications. MMOFs and PFS are bonded by hydrogen bonds, which enhance the polarity and dispersion of MMOFs, as well as the molecular chains of PFS. In the presence of MMOFs, it affected the distribution of iron species in the PFS, which means that the performance of coagulation may be changed. Coagulation with PFS-MMOFs was effective under different hydraulic conditions. It also showed better results than PFS in terms of dissolved organic carbon (DOC) removal and ultraviolet absorption value at 254 nm (UV₂₅₄). In addition, the PFS-MMOFs in algal-infested waters were superior to the PFS. Overall, the findings tested in this study indicated that MMOFs are good magnetic seeds for remediation of water pollution in conjunction with PFS, potentially enhancing conventional coagulation. Full article

Phosphorus (P) management in the “water-energy-resource-nexus” in wastewater treatment plants (WWTPs) remains a longstanding challenge. P adsorption from the P-enriched digested sludge liquor (DSL) is a comparatively more practical and economically viable approach for P recovery in WWTPs. However, high concentrations of impurities in DSL might pose a negative and interferential effect on P adsorption, hindering the application of sorbents or precipitation methods. Given such a situation, highly efficient and cost-effective sorbent towards P reclamation from DSL is highly needed. Therefore, this study aims to develop a novel complex agent containing aluminum coagulant and superparamagnetic nano-sorbent (SNS) that can be used in magnetic seeding coagulation for P recovery. The complex agents with different PACl: SNS ratios showed varied turbidity removal rates and P recovery efficiencies and the optimal ratio was 15 mg PACl: 15 g SNS. PAC and SNS showed significant interaction because PAC could enhance P adsorption by shielding the interferential effect of colloidal impurities. In addition, the complex is highly regenerative, with turbidity and P removal rate stably maintained at 70–80% after 10 adsorption/regeneration cycles. The cost–benefit analysis of the dosing complex agent showed a dosing cost of 0.154 EUR/m3, admittedly much higher than the conventional magnetic seeding coagulation, which could probably be covered by the profit if the expensive and rare P product is reclaimed. This work indicated that the complex agent was superior due to its high adsorption capacity, easy separation, and repeated dosing, and therefore had the potential for P recovery from DSL. Full article

A high concentration of suspended solids (SS) in swine wastewater reduces the efficiency of the biological treatment process. The current study developed a short-cut combined magnetic coagulation (MC)–sequence batch membrane bioreactor (SMBR) process to treat swine wastewater. Compared with the single SMBR process, the combined process successfully achieved similarly high removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (${\mathrm{N}\mathrm{H}}_4^{+}$-N), and total phosphorous (TP) of 96.0%, 97.6%, 99.0%, and 69.1%, respectively, at dosages of 0.5 g/L of poly aluminium chloride (PAC), 2 mg/L of polyacrylamide (PAM), and 1 g/L of magnetic seeds in Stage II, and concentrations of TN, COD, and ${\mathrm{N}\mathrm{H}}_4^{+}$-N in effluent can meet the discharge standards for pollutants for livestock and poultry breeding (GB18596-2001, China). The nitrogen removal loading (NRL) was increased from 0.21 to 0.28 kg/(m³·d), and the hydraulic retention time (HRT) was shortened from 5.0 days to 4.3 days. High-throughput sequencing analysis was carried out to investigate microbial community evolution, and the results showed that the relative abundance of ammonia-oxidizing bacteria (AOB) in the SMBR increased from 0.1% without pre-treatment to 1.78% with the pre-treatment of MC. Full article