Effects of different scrap iron as anode in Fe-C micro-electrolysis system for textile wastewater degradation

GO-CuO nanocomposites assimilated into CA-PES polymer membrane in adsorptive removal of organic dyes from wastewater

Textile industries are one of the leading environmental pollutants by releasing harmful dye effluents. In many textile distrts, the amount of excess color in treated textile effluent that exceeds regulatory limitations is still being a major concern. The combining usage of nanomaterials and polymer material to solve these issues using various techniques. In this research, graphene oxide-copper oxide (GO-CuO) nanomaterial have been incorporated into cellulose-acetate (CA), poly-ether sulfone (PES) blend polymer by using phase inversion process to fabricate thin film nanocomposite (TFN) membrane for removal of dye pollutant. The physiochemical properties of prepared TFN materials were studied by Fourier transform infra-red spectroscopy (FT-IR), X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), thermo gravimetric analysis (TGA), and mechanical strength analysis. Dye adsorption experiments were performed with four typical water-soluble organic dyes methylene blue (MB), rhodamine blue (Rh. B), methyl orange (MO) and Congo red (CR). After reaching adsorption equilibrium, the composite membrane final removal effectiveness for MB 92.42%, Rh. B 89.39%, CR 68.39%, and MO 58.82% respectively. As a result, the fabricated TFN material proves to be an effective adsorbent material for cationic dye molecules. Also, when the fabricated material was tested with textile industry effluent sample, all physio-chemical properties exhibited a considerable decrease in concentrations when compared to the real textile effluent concentration. The treated effluents permitted for a relatively greater growth and germination index of Tropical amaranth roots than the textile effluent, this demonstrates that phytotoxicity testing was also successful. The most effective temperature, concentration and pH were found to be 273 K, 1 × 10^-5 M and pH 9. The fabricated TFN membrane material (GO-CuO @ CA-PES) can be recommended for water treatment applications.

A novel constructed wetland based on iron carbon substrates: performance optimization and mechanisms of simultaneous removal of nitrogen and phosphorus

In recent years, the combination of iron carbon micro-electrolysis (ICME) with constructed wetlands (CWs) for removal of nitrogen and phosphorus has attracted more and more attention. However, the removal mechanisms by CWs with iron carbon (Fe-C) substrates are still unclear. In this study, the Fe-C based CW (CW-A) was established to improve the removal efficiencies of nitrogen and phosphorus by optimizing the operating conditions. And the removal mechanisms of nitrogen and phosphorus were explored. The results shown that the removal rates of COD, NH₄⁺-N, NO₃^--N, TN, and TP in CW-A could reach up to 84.4%, 94.0%, 81.1%, 86.6%, and 84.3%, respectively. Wetland plants and intermittent aeration have dominant effects on the removal of NH₄⁺-N, while the removal efficiencies of NO₃^--N, TN, and TP were mainly affected by Fe-C substrates, wetland plants, and HRT. XPS analysis revealed that Fe(0)/Fe²⁺ and their valence transformation played important roles on the pollutants removal. High-throughput sequencing results showed that Fe-C substrates and wetland plants had considerable impacts on the microbial community structures, such as richness and diversity of microorganism. The relative abundance of autotrophic denitrification bacteria (e.g., Denitatsoma, Thauera, and Sulfuritalea) increased in CW-A than CW-C. The electrons and H₂/[H] produced from Fe-C substrates were utilized by autotrophic denitrification bacteria for NO₃^--N reduction. Microbial degradation was the main removal mechanism of nitrogen in CW-A. Removal efficiency of phosphorus was enhanced resulted from the reaction of phosphate with iron ion. The application of CWs with Fe-C substrates and plants presented great potential for simultaneous removal of nitrogen and phosphorus.

Degradation of organic dye wastewater by H2O2-enhanced aluminum carbon micro-electrolysis

In this research, the treatment of methylene blue (MB) dye wastewater by a novel system that combines H₂O₂ with an aluminum-carbon micro-electrolysis (ACE) was explored. The effects of the H₂O₂ amount, initial pH, aluminum to carbon ratio, total aluminum-carbon mass, dye concentration, and reaction temperature on degradation of MB were investigated. The findings revealed that under the following conditions: H₂O₂ 34.0 mg/L, initial pH of 3.0, aluminum-to-carbon ratio of 2:1, total aluminum-carbon mass of 2.0 g/L, MB concentration of 20 mg/L, and 20 °C, the degradation rate of MB could reach 99.3% after 180 min, which is 18.4% more compared with ACE at the same conditions without H₂O₂. Through the quenching experiments, it was proved that the efficient free radicals produced during degradation are •OH and •O₂^-. Finally, a possible mechanism of H₂O₂ enhanced aluminum carbon micro-electrolysis (HP-ACE) for MB degradation was discussed.

Effect of iron nitrate modification on elimination of organic matter from landfill leachate by sludge-based activated carbon

Sludge-based activated carbons (SACs) prepared from sewage sludge and corn straw, were modified by ferric nitrate, and the unmodified SAC and modified SAC were used as the adsorbing agent to treat the landfill leachate, the elimination capacity for chemical oxygen demand (COD) and organic matter in leachate were studied. Based on this, the physicochemical properties of SACs and the components changes in leachate were analyzed and characterized by X-ray photoelectron spectroscopy and three-dimensional fluorescence spectroscopy. The results showed that under optimal experimental conditions, the elimination capacities of SAC372 for COD, biological oxygen demand over 5 days, and NH₄⁺-N in the leachate were 81.58%, 54.73%, and 69.08%, respectively; while the adsorption capacities of modified SAC for these three substances were 86.25%, 63.51%, and 79.15%, respectively. The ferric nitrate modification improved the ability of SAC to eliminate COD and organic matter from leachate slightly, and made the adsorption occurred easily. The adsorption process of unmodified SAC was dominated by multi-layer adsorption, while the adsorption process of modified SAC was dominated by monolayer adsorption. The mass fraction of Fe (2p) in modified SAC remarkably increased, from 0.70% to 26.01%, organic functional groups certain phase of Fe oxides with different valence states were generated in SAC, which provided a substrate for iron-carbon micro electrolysis. After adsorbed by unmodified SAC and modified SAC adsorption, the total fluorescence intensity of in the leachate increased by 17.01% and 116.84%, respectively. Both two SACs could decompose the humic acid-like substances into aromatic protein organic compounds, and modified SAC could further decompose the soluble microbial byproduct-like substances.

Removal mechanism of persistent organic pollutants by Fe-C micro-electrolysis

The degradation of persistent organic pollutants (POPs) in the simulated wastewaters was investigated by Fe-C micro-electrolysis system. With phenanthrene (PHE) and 2,4-dichlorophenol (2,4-DCP) as target pollutants, different iron-carbon (Fe-C) micro-electrolysis systems have been established. The effects of initial pH, Fe/C mass ratio, and intake air flow on the degradation and mineralization of PHE and 2,4-DCP were studied. At the initial pH of 5.0, Fe/C of 1.5:1, and an aeration flow rate of 1.5 L/min, after 120 min of reaction, the removal efficiency of FHE and COD was 94.3% and 73%, respectively. Under the conditions of initial pH is 3.0, Fe/C is 1:2, aeration flow rate of 1.5 L/min, and reaction time of 90 min, the best removal efficiency of 2,4-DCP can be obtained in the Fe-C micro-electrolysis system as 97% and COD removal efficiency can reach 76%. The results of kinetic studies show that the Fe-C micro-electrolysis process of PHE and 2,4-DCP follows pseudo-first-order kinetics. Commercial activated carbon (AC) was used for comparison under the same condition. The results indicated that the removal rate of organic pollutants and chemical oxygen demand (COD) of Fe-C micro-electrolysis were superior to that of AC. Analyze the structure of iron after reaction by SEM and XRD. The degradation pathway and mechanism for PHE and 2,4-DCP were proposed based on LC-MS analyses of treated wastewater.

Efficient bio-refractory industrial wastewater treatment with mitigated membrane fouling in a membrane bioreactor strengthened by the micro-scale ZVI@GAC galvanic-cells-initiated radical generation and coagulation processes

Micro-scale ZVI@GAC-based iron-carbon galvanic-cells (ZVI@GACs) were prepared with the Ca-Si-H/Ca-H formation process and first applied to initiate radical generation and coagulation processes in MBR for treating bio-refractory industrial wastewater (IWW). Batch tests revealed the H2O2 production (0.19-0.28 mg/L) and •OH generation (p-CBA decay, k1 = 0.040 min-1) in ZVI@GACs-dosed system (packing volume of 5%) under aeration. Adoption of ZVI@GACs into aerobic activated sludge process (ZVI@GACs/AS) enhanced TOC degradation (k2) and phenolic compounds (PHENs) destruction (k3). ZVI@GACs/AS at ZVI@GACs packing volume of 5%, 10% and 20% improved k2 from 0.11 h-1 (bare AS) to 0.17, 0.21 and 23 h-1 and k3 from 0.24 h-1 to 0.36, 0.49 and 0.57 h-1, respectively. The oxygen uptake rate (OUR) and 15-min acute bio-toxicity demonstrated that the bio-toxicity of IWW was reduced and the activity of biomass was enhanced in the ZVI@GACs/AS system. In MBR, ZVI@GACs at packing volume of 10% enhanced COD and PHENs removal by 14% and 22%, respectively. Membrane fouling cycle was prolonged by 71%. The accumulations of EPS-proteins, EPS-polysaccharides, SMP-proteins and SMP-polysaccharides were reduced by 6%, 67%, 27% and 60%, respectively. Fourier transform infrared spectroscopy (FTIR) confirmed the oxidation of SMP-polysaccharides in ZVI@GACs-MBR. The iron ions released from ZVI@GACs showed inhibition on the secretion of SMP-/EPS-proteins. Floc particle size distribution (PSD) and X-ray diffraction (XRD) spectrum confirmed that the coagulation effects of Fe(OH)3 and FeOOH triggered by Fe3+ increased the sludge floc size and contributed to membrane fouling mitigation. Genus Enterococcus was enriched in MBR with the destruction of PHENs by the ZVI@GACs-initiated radical generation process. The findings of this study confirmed successful development and adoption of ZVI@GACs into MBR for bio-refractory IWW treatment. It also provided an in-depth understanding on the mechanisms of ZVI@GACs-MBR system.

Macrolepiota-mediated synthesized silver nanoparticles as a green corrosive inhibitor for mild steel in re-circulating cooling water system

A simple, cost effective and eco-friendly silver nanoparticle (AgNPs) was synthesized by wild edible Macrolepiota mushroom. Nanoparticles were characterized by UV-visible, FTIR, XRD analysis and TEM analysis. The characterized studies confirmed the spherical shape of AgNPs with 20-50 nm size. Biocorrosion efficacy of myco-synthesized AgNPs and the mushroom extract were tested against mild steel by corrosive bacteria Bacillus thuringiensis EN2, Terribacillus aidingensis EN3 and Bacillus oleronius EN9. Weight loss analysis, EIS, and surface analysis were used to evaluate the corrosion inhibition efficiency of mild steel in various experimental systems. Reduced corrosion rate (0.07 mm/y, 0.14 mm/y), reduced weight loss (0.006 ± 2, 0.011 ± 2) and increased corrosion inhibition efficiency (59%, 18%) were identified in both system II and system IV. Peak intensity was reduced in both surface analysis studies (FTIR and XRD) in the presence of mushroom extract and AgNPs. EIS studies reveal that the mushroom extract and AgNPs act as a corrosive green inhibitor and adsorbs on the mild steel surfaces in cooling water tower system, which are responsible for corrosion protection.

Iron-carbon microelectrolysis for wastewater remediation: Preparation, performance and interaction mechanisms

Rapid industrialization and urbanization have produced a lot of hazardous substances in water and wastewater, which has turned into a crucial issue to the environment and the public health. Recently, iron carbon microelectrolysis (IC-ME) has attracted extensive attention in environmental remediation due to its low costs and excellent performance. Nevertheless, there is still a lack of a more systematic review on IC-ME preparation methods, their performance, and the interaction mechanisms of IC-ME in the remediation of wastewater. Herein, this work summarizes the synthetic methods, application of IC-ME materials, and the mechanism of pollutant removal by IC-ME. A variety approaches have been applied to prepare IC-ME materials, and the preparation methods and conditions have a certain influence on the properties of IC-ME materials, thus affecting the performance of pollutant removal. The mechanisms of IC-ME for contaminants removal are very complex, including adsorption, coprecipitation, reduction, surface complexation, and oxidation. Moreover, research vacant fields and problems that existed in the application of IC-ME are proposed. At last, the problems to be addressed to adapt IC to future applications are introduced. This paper reviews and prospects IC-ME wastewater remediation technology, which provides a reference for further scientific research and engineering applications.

Feasibility of iron scraps for enhancing nitrification of domestic wastewater at low temperatures

The development of an effective approach to improve low-temperature nitrification of domestic wastewater remains an important issue that needs to be urgently addressed. This study was intended to verify the feasibility of using iron scraps as an effective immobilization material to enhance nitrification activity in domestic wastewater-treatment systems at low temperatures. Iron scraps were tried and compared with one common immobilization material (PVA-SA embedded balls) in terms of low-temperature nitrification performances, anti-shock capacity, dynamics of microbial community, and economic costs. The results showed that compared with control, the average nitrification efficiency of iron scraps and PVA-SA embedded balls increased separately by 15.7% and 27.6% at low temperatures. Among these groups, the iron scrap-based group demonstrated the best anti-shock capacity and the smallest fluctuation (lower than 10%) with the shortening of HRT (hydraulic retention time) or the increase of inlet ammonium level. Nitrosomonas was found to be the dominant bacterial genera for these two immobilization materials. The increased costs of iron scraps and PVA-SA embedded balls were about ¥0.03 and ¥0.78 per ton of treated domestic wastewater. Taken together, iron scraps have some significant advantages including low costs, easy availability, and good anti-shock capacity, which make them a promising candidate for enhanced nitrification of domestic wastewater at low temperatures.

Synergetic effect of nano zero-valent iron and activated carbon on high-level ciprofloxacin removal in hydrolysis-acidogenesis of anaerobic digestion

Ciprofloxacin is the most commonly prescribed antibiotic, and its widespread use poses threat to environmental safety. The removal of ciprofloxacin from contaminated water has remained a major challenge. The present study investigated adding nanoscale zero-valent iron (NZVI) and activated carbon (AC) on high-level ciprofloxacin removal in hydrolysis-acidogenesis stage of anaerobic digestion. The results showed that the degradation rate of ciprofloxacin increased from 22.61% (Blank group) to 72.41% after adding NZVI/AC with concentration of ciprofloxacin in effluent decreasing from 8.25 mg L^-1 to 3.48 mg L^-1. The volatile fatty acids (VFAs) yield increased by 173.7% compared with the Blank group. In addition, the NZVI/AC group achieved the highest chemical oxygen demand (COD) removal rate and acidogenesis rate. The microbial community analysis presented that hydrolytic and acidogenic bacteria and microorganisms related to degrading ciprofloxacin were obviously improved in the NZVI/AC group. Moreover, eleven transformation products and the main degradation pathways were proposed based on mass spectrometry information. In summary, the NZVI/AC addition supplied promising approach for ciprofloxacin wastewater treatment.

Enhanced reactivity and electron selectivity of GAC-Fe-Cu ternary micro-electrolysis system toward p-chloronitrobenzene under oxic conditions

A novel GAC-Fe-Cu ternary micro-electrolysis system was synthesized for the removal of p-chloronitrobenzene (p-CNB) under oxic conditions. p-CNB could be efficiently removed by GAC-Fe-Cu at a wide initial pH range of 1.0-9.0. In particular, the p-CNB removal efficiency of 96.96 % was obtained at initial pH of 7.2, and the degradation (44.96 %) was the major removal pathway. Additionally, reduction and oxidation simultaneously contributed to the degradation of p-CNB. The results indicated that OH was the prime reactive species under acidic conditions while O₂^- dominated the degradation of p-CNB under neutral conditions. Reduction reaction was remarkably enhanced in the presence of dissolved oxygen and the iron corrosion could be accelerated by in-situ generated H₂O₂. Furthermore, XPS analysis of GAC-Fe-Cu revealed the surface-mediated electron transfer and oxidant generation process. The excellent degradation efficiency of p-CNB at initial pH of 7.2 was attributed to the enhanced electron selectivity of GAC-Fe-Cu as well as the high selectivity of near-surface generated O₂^- toward p-CNB and its intermediate products.

Preparation of a New Iron-Carbon-Loaded Constructed Wetland Substrate and Enhanced Phosphorus Removal Performance

Iron-carbon substrates have attracted extensive attention in water treatment due to their excellent processing ability. The traditional iron-carbon substrate suffers from poor removal effects, separation of the cathode and anode, hardening, secondary pollution, etc. In this study, a new type of iron-carbon-loaded substrate (NICLS) was developed to solve the problems of traditional micro-electrolytic substrates. Through experimental research, a preparation method for the NICLS with Fe and C as the core, zeolite as the skeleton, and water-based polyurethane as the binder was proposed. The performance of the NICLS in phosphorus-containing wastewater was analyzed. The results are as follows: The optimal synthesis conditions of the NICLS are 1 g hydroxycellulose, wood activated carbon as the cathode, an activated carbon particle size of 200-60 mesh, and an Fe/C ratio of 1:1. Acidic conditions can promote the degradation of phosphorus by the NICLS. Through the characterization of the NICLS (scanning electron microscope (SEM), X-ray diffractometer (XRD), and energy-dispersive spectrometer (EDS), etc.), it is concluded that the mechanism of the NICLS phosphorus removal is a chemical reaction produced by micro-electrolysis. Using the NICLS to treat phosphorus-containing wastewater has the advantages of high efficiency and durability. Therefore, it can be considered that the NICLS is a promising material to remove phosphorus.

New insights into the reinforced reduction performance of Fe0/C internal electrolysis activated by persulfate for p-nitrophenol removal

In this study, the reduction of iron-carbon internal electrolysis was reinforced by persulfate for p-nitrophenol removal. The effects of persulfate dosage, initial pH and iron-carbon mass ratio were comprehensively studied in batch experiments. In the system of iron-carbon internal electrolysis coupled with persulfate, the iron-carbon internal electrolysis and persulfate had a significant mutual influence, exhibiting a wide range of pH in the treatment process. Moreover, the coupled system also showed the remarkable removal and degradation efficiency of p-nitrophenol according to the contrast experiments. The satisfactory results should be attributed to the potential reduction of iron-carbon internal electrolysis, which was stimulated by persulfate to transform the nitro group to the amine group, accompanying the subsequent oxidation. Furthermore, persulfate possessed the ability that the dynamically destructive effect on external and internal of Fe⁰ and the scavenging action on activated carbon, effectively strengthening the potential energy for release and transfer of reductive substances. Both HO^• and SO₄^•- as the main free radicals were formed to mineralize the intermediates in the coupled system. These findings indicate that the system of iron-carbon internal electrolysis coupled with persulfate can be a promising strategy for the treatment of the toxic and refractory wastewater.