Phenol removal kinetics from synthetic wastewater by activation of persulfate using a catalyst generated from shipping ports sludge

Synthesis of iron nanoparticles using iron recovered from rust: An application for the catalytic degradation of phenols

Iron nanoparticles are reported to be synthesised by green route to reduce adverse environmental impacts as well as to reduce the synthesis cost. The present study explores a secondary source of iron, i.e. waste iron rust to prepare iron nanoparticles via green route. The iron nanoparticles synthesised this way were amorphous. The synthesised nanoparticles were used as a heterogeneous catalyst for the purpose of phenol and p-nitrophenol (PNP) degradation in their aqueous solutions by Fenton degradation. More than 95% of phenol and PNP was removed within 120 min using 0.25 g/L amount of catalyst. The degradative removal of both the pollutants was found effective up to pH 6. Pseudo-second-order kinetic was fitted best the degradation data of the pollutants. The dissolution of catalyst iron by corrosion was analysed by testing the amount of iron leached and dissolved into the aqueous solution of phenol and PNP; maximum concentration of total iron was found 11.10 mg/L in phenol and 13.53 mg/L in PNP. The chemical oxygen demand (COD) was decreased to 40 mg/L from 336 mg/L for phenol and COD of PNP solution was decreased up to 56 mg/L from 384 mg/L.

A review on recent advancements in the treatment of polyaromatic hydrocarbons (PAHs) using sulfate radicals based advanced oxidation process

Polyaromatic hydrocarbons (PAHs) are the most persistent compounds that get contaminated in the soil and water. Nearly 16 PAHs was considered to be a very toxic according US protection Agency. Though its concentration level is low in the environments but the effects due to it, is enormous. Advanced Oxidation Process (AOP) is an emergent methodology towards treating such pollutants with low and high molecular weight of complex substances. In this study, sulfate radical (SO4‾•) based AOP is emphasized for purging PAH from different sources. This review essentially concentrated on the mechanism of SO4‾• for the remediation of pollutants from different sources and the effects caused due to these pollutants in the environment was reduced by this mechanism is revealed in this review. It also talks about the SO4‾• precursors like Peroxymonosulfate (PMS) and Persulfate (PS) and their active participation in treating the different sources of toxic pollutants. Though PS and PMS is used for removing different contaminants, the degradation of PAH due to SO4‾• was presented particularly. The hydroxyl radical (•OH) mechanism-based methods are also emphasized in this review along with their limitations. In addition to that, different activation methods of PS and PMS were discussed which highlighted the performance of transition metals in activation. Also this review opened up about the degradation efficiency of contaminants, which was mostly higher than 90% where transition metals were used for activation. Especially, on usage of nanoparticles even 100% of degradation could be able to achieve was clearly showed in this literature study. This study mainly proposed the treatment of PAH present in the soil and water using SO4‾• with different activation methodologies. Particularly, it emphasized about the importance of treating the PAH to overcome the risk associated with the environment and humans due to its contamination.

Enhancing photodegradation of thiamethoxam insecticide using SnS2/NCL as a photocatalyst: Mechanistic insights and environmental implications

The current research highlights the fabrication of a novel SnS2/CO32-@Ni-Co LDH (SnS2/NCL) by precipitating Ni-Co LDH over hydrothermally synthesized SnS2 nanoparticles for the enhanced degradation of thiamethoxam (THM) insecticide through the advanced oxidation process. The effect of several reaction parameters was optimized, and a maximum degradation of 98.1 ± 1.2 % with a rate constant of 0.0541 min-1 of 10 ppm THM was reached at a catalyst loading of 0.16 gL-1 using 0.3 mM of H2O2 within 70 min of visible light irradiation. The effect of metal cations, inorganic anions, dissolved organic matter, organic compounds and water samples on the photodegradation performance of SnS2/NCL nanocomposite was also examined to evaluate the prepared photocatalyst's suitability for use in actual wastewater conditions. The metal cations blocked the active sites of the photocatalyst and reduced the degradation efficiency except for Fe2+ ions, since it is a Fenton reagent and increased the production of hydroxyl radicals. Inorganic anions are the scavengers of hydroxyl radicals and hinder photocatalytic activity. Meanwhile, lake water containing varying degrees of co-existing ions shows the lowest degradation efficiency among other water samples. The SnS2/NCL nanocomposite could be reused for five cycles while maintaining a photocatalytic efficiency of 83.6 ± 0.3 % in the fifth run. The prepared SnS2/NCL nanocomposite also showed excellent photodegradation of several other emerging organic pollutants with an efficiency of over 80 % under optimum conditions. Incorporating Ni-Co LDH with SnS2 helped to delocalize photoinduced charges, leading to increased photocatalytic activity and a slower electron-hole recombination rate. The present research highlights the photocatalytic activity of SnS2/NCL photocatalysts for the photocatalytic degradation of emerging contaminants from wastewater.

Removal of Iron and Copper Ions and Phenol from Liquid Phase by Membrane Based on Carbonaceous Materials

The present work reports an effective method for the removal of inorganic and organic pollutants using membranes based on different carbonaceous materials. The membranes were prepared based on cellulose acetate (18 wt. %), polyvinylpyrrolidone as a pore-generating agent (2 wt. %) and activated carbon (1 wt. %). Activated carbons were developed from residues after extraction of the mushroom Inonotus obliguus using microwave radiation. It has been demonstrated that the addition of activated carbon to the membranes resulted in alterations to their physical properties, including porosity, equilibrium water content and permeability. Furthermore, the chemical properties of the membranes were also affected, with changes observed in the content of the surface oxygen group. The addition of carbon material had a positive effect on the removal of copper ions from their aqueous solutions by the cellulose-carbon composites obtained. Moreover, the membranes proved to be more effective in the removal of copper ions than iron ones and phenol. The membranes were found to show higher effectiveness in copper removal from a solution of the initial concentration of 800 mg/L. The most efficient in copper ions removal was the membrane containing urea-enriched activated carbon.

Bandgap engineering approach for synthesising photoactive novel Ag/HAp/SnS2 for removing toxic anti-fungal pharmaceutical from aqueous environment

The present work shed light on synthesising a novel ternary Z-scheme Ag/HAp/SnS2 (AHS) nano photocatalyst to degrade metronidazole (MTZ) in wastewater through H2O2-assisted AOP under natural sunlight. HAp extracted from the fish scales of rohu fish through alkaline treatment was decorated with Ag nanoparticles using ascorbic acid as a bio-reductant. Tin disulphide (SnS2) was anchored over Ag/HAp to prevent agglomeration and enhance photocatalytic activity by delaying the electron-hole recombination rate. After 45 min of irradiation, a degradation efficiency of 98.85 ± 1.86% for 15 ppm MTZ could be achieved. The performance of the prepared photocatalyst in real wastewater was investigated by introducing several metal cations and anions in the photodegradation process. The degradation products were identified by HRLCMS analysis, and the breakdown mechanism of MTZ was proposed. The present study enlightens the importance of SnS2-based photocatalysts for organic pollutant degradation under natural sunlight through an advanced oxidation process. The characterization results showed that the enhanced photodegradation efficiency of AHS is attributed to the formation of an all-solid-state Z-scheme heterojunction with Ag nanoparticles acting as charge transfer medium and as electron accumulators helping in delaying charge recombination.

Application of pier waste sludge for catalytic activation of proxy-monosulfate and phenol elimination from a petrochemical wastewater

This investigation aimed to remove phenol from real wastewater (taken from a petrochemical company) by activating peroxy-monosulfate (PMS) using catalysts extracted from pier waste sludge. The physical and chemical properties of the catalyst were evaluated by FE-SEM/EDS, XRD, FTIR, and TGA/DTG tests. The functional groups of O-H, C-H, CO₃^2-, C-H, C-O, N-H, and C-N were identified on the catalyst surface. Also, the crystallinity of the catalyst before and after reaction with petrochemical wastewater was 103.4 nm and 55.8 nm, respectively. Operational parameters of pH (3-9), catalyst dose (0-100 mg/L), phenol concentration (50-250 mg/L), and PMS concentration (0-250 mg/L) were tested to remove phenol. The highest phenol removal rate (94%) was obtained at pH=3, catalyst dose of 80 mg/L, phenol concentration of 50 mg/L, PMS concentration of 150 mg/L, and contact time of 150 min. Phenol decomposition in petrochemical wastewater followed the first-order kinetics (k> 0.008 min^-1, R²> 0.94). Changes in pH factor were very effective on phenol removal efficiency, and maximum efficiency (≈83%) was achieved in pH 3. The catalyst stability test was performed for up to five cycles, and phenol removal in the fifth cycle was reduced to 42%. Also, the energy consumption in this study was 77.69 kW h/m³. According to the results, the pier waste sludge catalyst/PMS system is a critical process for eliminating phenol from petrochemical wastewater.

Fe-zeolite catalyst for ozonation of pulp and paper wastewater for sustainable water resources

The pulp and paper industry consumes enormous quality of freshwater, leading to wastewater. It must be treated to remove pollutants, particularly residual dyestuffs, before releasing them to water bodies to avoid adverse environmental effects. The traditional wastewater treatment methods used for the pulp and paper industry are less efficient in colour and chemical oxygen demand (COD) removal. The current study is aimed at developing a novel catalyst for the catalytic ozonation of pulp and paper wastewater with better colour and COD removal for sustainable resources of clean water. The proposed catalyst is impregnated by iron on natural zeolites. Various parameters such as catalyst dose, pH, ozone dose, initial COD concentration, and reaction time are studied and optimized. The performance was evaluated by comparing the results with the single ozonation process (SOP) and catalytic ozonation process (COP). The highest COD and colour reduction efficiencies have been achieved, i.e., 71%, and 88% at a natural pH of 6.8. The proposed process achieved higher COD and colour efficiencies than the single ozonation process and catalytic ozonation process using raw zeolites. The improvement in efficiencies are 23% and 29% for SOP and 17% and 19% for COP, respectively. Hence, the results proposed the sustainability and applicability of COP to treat paper and pulp sector effluent.

Phenol and 17β-estradiol removal by Zoogloea sp. MFQ7 and in-situ generated biogenic manganese oxides: Performance, kinetics and mechanism

The pollution of multifarious pollutants such as heavy metal, organic compounds, and nitrate are a hot research topic at present. In this study, the functions of Zoogloea sp. MFQ7 and its biological precipitation formed during bacterial manganese oxidation on the removal of phenol and 17β-estradiol (E2) were investigated. Strain MFQ7, a manganese-oxidizing bacteria, can remove 98.34% of phenol under pH of 7.1, a temperature of 30 ℃ and Mn²⁺ concentration of 24.34 mg L^-1, additionally, the optimum E2 removal by strain MFQ7 was 100.00% at pH of 7.1, temperature of 28 ℃ and Mn²⁺ concentration of 28.45 mg L^-1 by using response surface methodology (RSM) based on Box-Behnken design (BBD) model. The maximum adsorption capacity of bio-precipitation for phenol and E2 was 201.15 mg g^-1 and 65.90 mg g^-1, respectively. Furthermore, adsorption kinetics and isotherms analysis, XPS, FTIR spectra, Mn(III) trapping experiments elucidated chemical adsorption and Mn(III) oxidation contribute to the removal of phenol and E2 by biogenic manganese oxides. These findings indicated that the adsorption and oxidation of manganese are expected to be one of the effective means to remove these typical organic pollutants containing phenol and E2.

Iron-based materials for simultaneous removal of heavy metal(loid)s and emerging organic contaminants from the aquatic environment: Recent advances and perspectives

The existence of heavy metals and emerging organic contaminants in wastewater produces serious toxic residues to the environment. Developing cheap and efficient materials to remove these persistent pollutants is crucial. Iron-based materials are cost-effective and environmentally friendly catalysts, and their applications in the environmental field deserve attention. This paper critically reviewed the removal mechanisms of heavy metals and emerging organic pollutants by different influencing factors. The removal of pollutants (heavy metals and emerging organic pollutants) in a multi-component system was analyzed in detail. The mechanisms of synergism, antagonism and non-interference were discussed. This paper had a certain reference value for the research of wastewater remediation technology which could simultaneously remove various pollutants by iron-based materials.

Denitrification performance of nitrate-dependent ferrous (Fe2+) oxidizing Aquabacterium sp. XL4: Adsorption mechanisms of bio-precipitation of phenol and estradiol

In this study, a nitrate-dependent ferrous (Fe²⁺) oxidizing strain under anaerobic conditions was selected and identified as XL4, which belongs to Aquabacterium. The Box-Behnken design (BBD) was used to optimize the growth conditions of strain XL4, and the nitrate removal efficiency of strain XL4 (with 10% inoculation dosage, v/v) could reach 91.41% under the conditions of 30.34 ℃, pH of 6.91, and Fe²⁺ concentration of 19.69 mg L^-1. The results of Fluorescence excitation-emission matrix spectra (EEM) revealed that the intensity of soluble microbial products (SMP), aromatic proteins and the fulvic-like materials were obvious difference under different Fe²⁺ concentration, pH, and temperature. X-ray diffraction (XRD) data confirmed that the main components of bio-precipitation were Fe₃O₄ and FeO(OH), which were believed to be responsible for the adsorption of phenol and estradiol. Furthermore, the maximum adsorption capacity of bio-precipitation for phenol and estradiol under the optimal conditions were 192.6 and 65.4 mg g^-1, respectively. On the other hand, the adsorption process of phenol and estradiol by bio-precipitation confirmed to the pseudo-second-order and Langmuir model, which shows that the adsorption process is chemical adsorption and occurs on the uniform surface.

Enhanced nitrate, manganese, and phenol removal by polyvinyl alcohol/sodium alginate with biochar gel beads immobilized bioreactor: Performance, mechanism, and bacterial diversity

Water pollutants, such as nitrate, heavy metals, and organics have attracted attention due to their harms to environmental and biological health. A novel polyvinyl alcohol/sodium alginate with biochar (PVA/SA@biochar) gel beads immobilized bioreactor was established to remove nitrate, manganese, and phenol. The optimum conditions for preparing gel beads were studied by response surface methodology (RSM). Notably, the removal efficiencies of nitrate, Mn(II), and phenol were 94.64, 72.74, and 93.97% at C/N of 2.0; the concentrations of Mn(II) and phenol were 20 and 1 mg L^-1, respectively. Moreover, addition of different concentrations of phenol significantly affected the components of dissolved organic matter, bacterial activity, and bioreactor performance. The biological manganese oxide (BMO) with three-dimensional petal-type structure produced during Mn(II) oxidation showed excellent adsorption capacity. The removal of phenol relied on a combination of biological action and adsorption processes. High-throughput analysis showed that Zoogloea sp. was the predominant bacterial group.

Elimination of amoxicillin using zeolite Y-sea salt as a good catalyst for activation of hydrogen peroxide: Investigating degradation pathway and the effect of wastewater chemistry

The sea contains elements that can play a useful role in catalyzing reactions. Therefore, this research was done to focus on eliminating amoxicillin (AMX) from wastewater utilizing zeolite Y- sea salt catalyst in the presence of H₂O₂. The influences of furnace temperature (200-500 °C) and time duration in the furnace (1-4 h) were optimized during catalyst generation. Also, the effects of different parameters on AMX removal, such as pH (5.0-9.0), catalyst dose (0-10 g.L^-1), AMX concentration (50-300 mg.L^-1), contact time (10-130 min), and H₂O₂ concentration (0-6 mL/100 mL distilled water) were investigated. Different analyses like Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were conducted to reveal catalyst properties. The BET-specific surface area of the catalyst (12.69 m²g^-1) insignificantly (p-value > 0.05) changed after AMX removal (13.04 m²g^-1), indicating the strength of the prepared catalyst. The active groups of N-H, O-H-O, O-Si-O, C-H, Si-O-Si, and Si-O-Al were determined in the catalyst structure. The highest removal of AMX (93%) was achieved in the zeolite-sea salt/H₂O₂ system at a pH level of 6.0 and an H₂O₂ concentration of 0.1 mL/100 mL. Elimination of the AMX followed pseudo-first-order kinetics. The catalyst was reclaimed up to 7 times and the removal efficiency was suitable up to the fifth stage. The by-products and reaction pathways were investigated by gas chromatography-mass spectrometry (GC-MS). The results showed that zeolite-sea salt can be utilized as an H₂O₂ activator for the effective degradation of AMX from wastewater.

Activation of peroxydisulfate by ball-milled α-FeOOH/biochar composite for phenol removal: Component contribution and internal mechanisms

Persulfate-based advanced oxidation process is considered as a promising technology for the degradation of phenol, where efficient, cost effective, and green methods with high peroxydisulfate (PS) activation capacity is of increasing demand. In this work, an in-situ liquid phase precipitation combined with ball milling method was applied for the synthesized of α-FeOOH/biochar, as be the PS activator for phenol degradation. Results showed that the ball-milled α-FeOOH and red pine wood biochar prepared at 700 °C (BM-α-FeOOH/PBC700) exhibited the highest catalytic property with PS for phenol oxidation (a phenol removal rate of 100%), compared with the BM-α-FeOOH (16.0%) and BMPBC700 (66.3%). The presence of intermediate products such as hydroquinone and catechol, and total organic carbon (TOC) removal rate (88.9%) proved the oxidation of phenol in the BM-α-FeOOH/PBC700+PS system. The characterization results showed that the functional groups (e.g., CO, C-O, Fe-O, and Si-O), the dissolved organic matter (DOM) in biochar, the loading of Fe element, and higher degree of graphitization and defect structures, contributed to the activation of PS to form free radicals (i.e., SO₄^·-, ·OH, ·O₂^-, and h_VB⁺) for phenol oxidation, of which, SO₄·^- and ·OH account for 72.1% of the phenol removal rate. The specific contribution to the PS activation for phenol oxidation by each part of the materials was calculated based on the "whole to part" experiment. The contribution of DOM, acid-soluble substance, and carbon matrix and basal part in BM-α-FeOOH/PBC700 were 6.0%, 40.9%, and 53.1%, respectively. The reusability experiments of BM-α-FeOOH/PBC700 demonstrated that the composite was relatively stable after four cycles of reuse. Among three co-existing anions (NO₃^-, Cl^-, and HCO₃^-), HCO₃^- played the most significant inhibition effects on phenol removal through reducing the phenol removal rate from 89.6% to 77.9%. This work provides guidance for the design of high active and stable carbon materials that activate PS to remove phenol.