CuO nanosheets incorporated scrap steel slag coupled with persulfate catalysts for high-efficient degradation of sulfonamide from water

Potential of metallurgical iron-containing solid waste-based catalysts as activator of persulfate for organic pollutants degradation

The production of solid wastes in the metallurgical industry has significant implications for land resources and environmental pollution. To address this issue, it is crucial to explore the potential of recycling these solid wastes to reduce land occupation while protecting the environment and promoting resource utilization. Steel slag, red mud, copper slag and steel picking waste liquor are examples of solid wastes generated during the metallurgical process that possess high iron content and Fe species, making them excellent catalysts for persulfate-based advanced oxidation processes (PS-AOPs). This review elucidates the catalytic mechanisms and pathways of Fe2+ and Fe0 in the activation PS. Additionally, it underscores the potential of metallurgical iron-containing solid waste (MISW) as a catalyst for PS activation, offering a viable strategy for its high-value utilization. Lastly, the article provides an outlook towards future challenges and prospects for MISW in PS activation for the degradation of organic pollutants.

Fabrication of nano-hammer shaped CuO@HApNWs for catalytic degradation of tetracycline

With widespread and excessive use of antibiotics in medicine, poultry farming, and aquaculture, antibiotic residues have become a significant threat to both eco-environment and human health. In this paper, using hydroxyapatite nanowires (HApNWs) as an ecologically compatible carrier, a novel nano-hammer shaped conjunction with HApNW conjugating CuO microspheres (CuO@HApNWs) was successfully synthesized by in-situ agglomeration method. The catalytic degradation performance of the nano-hammer shaped CuO@HApNWs with Fenton-like activation was investigated by using tetracycline (TC) as a representative antibiotic pollutant. Remarkably, it exhibited excellent catalytic activity, which the removal rate of TC got to 92.0% within 40 min, and the pseudo-second-order reaction kinetic constant was 18.33 × 10-3 L mg-1·min-1, which was 26 times and 5 times than that of HApNWs and CuO, respectively. Furthermore, after recycling 6 times, the degradation efficiency of TC still remained above 85 %. Based on radical scavenger tests and electron paramagnetic resonance (EPR) spectroscopy, it demonstrated that the excellent activity of CuO@HApNWs was mainly attributed to the fact that Fenton-like activation promotes the circulation of Cu2+ and Cu+, the generated main active oxygen species (•OH and O2-•) achieve efficient degradation of TC. In summary, the nano-hammer shaped CuO@HApNWs could be in-situ synthesed, and used as an eco-friendly Fenton-like catalyst for effectively catalytic degradation of organic pollutants, which has great potential for wastewater treatment.

Microwave deicing properties and carbon emissions assessment of asphalt mixtures containing steel slag towards resource conservation and waste reuse

A large amount of solid waste, such as steel slag (SS), is generated annually. At the same time, the shortage of road construction materials is becoming a concern. In this study, to recycle and reuse SS as a substitute for natural aggregates to achieve resource conservation and sustainable development of roads were conducted. First, the electromagnetic performance of SS was explored to evaluate its wave-absorbing properties. Next, the effect of different SS contents on heating properties, surface temperature, heating uniformity, and ice melting time (IMT) were investigated. Finally, the carbon emissions assessment (CEA) of conventional asphalt mixture (CAM) and steel slag asphalt mixture (SSAM) was compared. Results indicated that SS has ferromagnetic behavior and higher electromagnetic parameters, showing better wave-absorbing properties than limestone. There were three stages during microwave heating (MH): ice melting, moisture emitting, and stabilization. In addition, heating uniformity tends to be poor with the increase of SS, and samples with 100 % content of SS have the highest standard deviation of 21.04 °C and 20.77 °C after 270 s at -10 °C and - 20 °C. Samples containing 50 % SS have the best microwave deicing properties, which can reduce the IMT by 28.57 % to 46.18 % at different initial freezing temperatures and ice thickness compared to CAM. Furthermore, CEA revealed that CAM and SSAM's carbon emissions over road construction's life cycle are similar (around 27,000 kg) and originate mainly from the mixing and raw material extraction phases. However, SSAM leads to better environmental and economic benefits and provides an exemplary resource conservation and waste reuse solution.

A review of metallurgical slags as catalysts in advanced oxidation processes for removal of refractory organic pollutants in wastewater

With the rapid growth of the metallurgical industry, there is a significant increase in the production of metallurgical slags. The waste slags pose significant challenges for their disposal because of complex compositions, low utilization rates, and environmental toxicity. One promising approach is to utilize metallurgical slags as catalysts for treatment of refractory organic pollutants in wastewater through advanced oxidation processes (AOPs), achieving the objective of "treating waste with waste". This work provides a literature review of the source, production, and chemical composition of metallurgical slags, including steel slag, copper slag, electrolytic manganese residue, and red mud. It emphasizes the modification methods of metallurgical slags as catalysts and the application in AOPs for degradation of refractory organic pollutants. The reaction conditions, catalytic performance, and degradation mechanisms of organic pollutants using metallurgical slags are summarized. Studies have proved the feasibility of using metallurgical slags as catalysts for removing various pollutants by AOPs. The catalytic performance was significantly influenced by slags-derived catalysts, catalyst modification, and process factors. Future research should focus on addressing the safety and stability of catalysts, developing green and efficient modification methods, enhancing degradation efficiency, and implementing large-scale treatment of real wastewater. This work offers insights into the resource utilization of metallurgical slags and pollutant degradation in wastewater.

Plasma synthesis of oxygen vacancy-rich CuO/Cu2(OH)3NO3 heterostructure nanosheets for boosting degradation performance

Defect regulation and the construction of a heterojunction structure are effective strategies to improve the catalytic activity of catalysts. In this work, the rapid conversion of CuO to Cu2(OH)3NO3 was achieved by fixing nitrogen in air as NO3- using dielectric barrier discharge (DBD) plasma. This innovative approach resulted in the successful synthesis of a CuO/Cu2(OH)3NO3 nanosheet heterostructure. Notably, the samples prepared using plasma exhibit thinner thickness and larger specific surface area. Importantly, oxygen vacancies are introduced, simultaneously forming heterojunction interfaces within the CuO/Cu2(OH)3NO3 structure. CuO/Cu2(OH)3NO3 using plasma effectively degraded 96% of methyl orange within 8 min in the dark. The degradation rate is 81 and 23 times that of CuO and Cu2(OH)3NO3 using hydrothermal methods, respectively. The high catalytic activity is attributed to the large specific surface area, the abundance of active sites, and the synergy between oxygen vacancies and the strong heterojunction interfacial interactions, which accelerate the transfer of electrons and the production of reactive oxygen species (˙O2- and ˙OH). The mechanism of plasma preparation was proposed on account of microstructure characterization and online mass spectroscopy, which indicated that gas etching, gas expansion, and the repulsive force of electrons play key roles in plasma exfoliation.

Activation of peroxymonosulfate with biochar-supported CuO (CuO@BC) for natural organic matter removal and membrane fouling control

To achieve excellent activation efficiency of peroxymonosulfate (PMS), this work prepared a biochar-supported CuO (CuO@BC) catalyst, and the CuO@BC/PMS system was proposed to remove the organic matter in natural surface water and reduce the fouling of ultrafiltration membrane. The successful synthesis of CuO@BC was demonstrated through characterization of its microscopic morphology and chemical composition by various techniques. The prepared heterogeneous catalyst showed a strong catalytic effect on PMS, which significantly removed natural organic matter through the production of active substances (•OH, SO4•-, O2•- and 1O2) from water. With respective degradation rates of 39.4% and 59.4%, the concentrations of DOC and UV254 dropped to 1.702 mg/L and 0.026 cm-1, respectively. Additionally, the CuO@BC/PMS oxidation displayed potent oxidation capabilities for contaminants and fluorescent organics with various molecular weights. The system effectively decreased the amount of organic matter that caused reversible and irreversible fouling of polyethersulfone membranes in natural water by 85.8% and 56.3%, respectively. The main fouling mechanisms changed as well, with standard and complete blocking dominating the entire filtration process. The results demonstrated the capacity of the CuO@BC/PMS system to remove contaminants in natural water and mitigate membrane fouling.

In-situ synthesis of magnetic iron-chitosan-derived biochar as an efficient persulfate activator for phenol degradation

Persulfate activation is a forceful method for eliminating organic pollutants from coal chemical wastewater. In this study, an in-situ synthesis method was used to fabricate an iron-chitosan-derived biochar (Fe-CS@BC) nanocomposite catalyst using chitosan as a template. Fe was successfully imprinted into the newly synthesized catalyst. The Fe-CS@BC can activate persulfate to effectively degrade phenol. This point was confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The impact of various parameters on the removal rate was investigated in a single factor experiment. In Fe-CS@BC/PDS system, 95.96% of phenol (significantly higher than the original biochar of 34.33%) was removed within 45 min and 54.39% TOC within 2 h. The system showed superior efficiency over a broad pH value band from 3 to 9 and has a high degradation rate at ambient temperature. Free radical quenching experiment, EPR experiment and LSV experiment confirmed that multiple free radicals (including 1O2, SO4•-, O2•- and •OH) and electron transfer pathway combined to enhance phenol decomposition. Finally, the activation mechanism of persulfate by Fe-CS@BC was proposed to provide logical guidance on the treatment of organic pollutants in coal chemical wastewater.

Ultrafast short-range catalytic pathway modified peroxymonosulfate activation over CuO with surface oxygen defects for tetracycline hydrochloride degradation

The presence of antibiotics in water bodies seriously threatens the ecosystem and human health. Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS), an effective method to remove antibiotics, have a bottleneck problem that the low oxidant utilization is attributed to the hindered electron transfer between metal oxides and peroxides. Here, CuO with rich oxygen vacancies (OVs), MSCuO-300, was synthesized to efficiently degrade tetracycline hydrochloride (TTCH) (k = 0.095 min^-1). The dominant role of direct adsorption and activation of OVs and its regulated Cu-O, rather than surface hydroxyl adsorption, mediated a short-range catalytic pathway. The shortened catalytic pathway between active sites and PMS accelerated the charge transfer at the interface, which promoted PMS activation. Compared with Cu_xO-500 and Commercial CuO, the activation rate of PMS was increased by 11.97, and 12.64 times, respectively. OVs contributed to the production of ¹O₂ and O₂^•-, the main active species. In addition, MSCuO-300/PMS showed excellent adaptability to real water parameters, such as pH (3-11), anions, and continuous reactor maintained for 168 h. This study provides a successful case for the purification of antibiotic-containing wastewater in the design of efficient catalysts by oxygen defect strategies.

Sulfate radicals-based advanced oxidation processes for the degradation of pharmaceuticals and personal care products: A review on relevant activation mechanisms, performance, and perspectives

Owing to the rapid development of modern industry, a greater number of organic pollutants are discharged into the water matrices. In recent decades, research efforts have focused on developing more effective technologies for the remediation of water containing pharmaceuticals and personal care products (PPCPs). Recently, sulfate radicals-based advanced oxidation processes (SR-AOPs) have been extensively used due to their high oxidizing potential, and effectiveness compared with other AOPs in PPCPs remediation. The present review provides a comprehensive assessment of the different methods such as heat, ultraviolet (UV) light, photo-generated electrons, ultrasound (US), electrochemical, carbon nanomaterials, homogeneous, and heterogeneous catalysts for activating peroxymonosulfate (PMS) and peroxydisulfate (PDS). In addition, possible activation mechanisms from the point of radical and non-radical pathways are discussed. Then, biodegradability enhancement and toxicity reduction are highlighted. Comparison with other AOPs and treatment of PPCPs by the integrated process are evaluated as well. Lastly, conclusions and future perspectives on this research topic are elaborated.