A review on efficient removal of phthalic acid esters via biochars and transition metals-activated persulfate systems

Biodegradation of phthalic acid and terephthalic acid by Comamonas testosteroni strains

Phthalic acid isomers are the monomers of phthalate molecules, also known as phthalic acid esters, widely employed in the plastics industry. This study aims to investigate the biodegradation of phthalic acid (PA) and terephthalic acid (TPA) by five industry-borne Comamonas testosteroni strains: 3APTOL, 3ABBK, 2B, 3A1, and C8. To assess the ability of C. testosteroni strains to biodegrade phthalic acid isomers in fermentation media, an analytical method was employed, consisting of high-performance liquid chromatography (HPLC) analyses. Subsequently, molecular screening of the genomic and plasmid DNA was conducted to identify the degradative genes responsible for the breakdown of these chemicals. The genes of interest, including ophA2, tphA2, tphA3, pmdA, and pmdB, were screened by real-time PCR. The five C. testosteroni strains effectively degraded 100% of 100 mg/L PA (p = 0.033) and TPA (p = 0.0114). Molecular analyses indicated that all C. testosteroni strains contained the pertinent genes at different levels within their genomes and plasmids, as reflected in the threshold cycle (Ct) values. Additionally, DNA temperature of melting (Tm) analyses uncovered minor differences between groups of genes in genomic and plasmid DNA. C. testosteroni strains could be excellent candidates for the removal of phthalic acid isomers from environmental systems.

Degradation of dimethyl phthalate by morphology controlled β-MnO2 activated peroxymonosulfate: The overlooked roles of high-valent manganese species

Activated peroxymonosulfate (PMS) processes have emerged as an efficient advanced oxidation process to eliminate refractory organic pollutants in water. This study synthesized a novel spherical manganese oxide catalyst (0.4KBr-β-MnO2) via a simple KBr-guided approach to activate PMS for degrading dimethyl phthalate (DMP). The 0.4KBr-β-MnO2/PMS system enhanced DMP degradation under different water quality conditions, exhibiting an ultrahigh and stable catalytic activity, outperforming equivalent quantities of pristine β-MnO2 by 8.5 times. Mn(V) was the dominant reactive species that was revealed by the generation of methyl phenyl sulfone from methyl phenyl sulfoxide oxidation. The selectivity of Mn(V) was demonstrated by the negligible inhibitory effects of Inorganic anions. Theoretical calculations confirmed that Mn (V) was more prone to attack the CO bond of the side chain of DMP. This study revealed the indispensable roles of high-valent manganese species in DMP degradation by the 0.4KBr-β-MnO2/PMS system. The findings could provide insight into effective PMS activation by Mn-based catalysts to efficiently degrade pollutants in water via the high-valent manganese species.

Efficient degradation of norfloxacin using a novel biochar-supported CuO/Fe3O4 combined with peroxydisulfate: Insights into enhanced contribution of nonradical pathway

Nonradical persulfate oxidation techniques have evolved as a new contaminated water treatment approach due to its great tolerance to water matrixes. The catalysts of CuO-based composites have received much attention in that aside from SO₄^•-/^•OH radicals, the nonradicals of singlet oxygen (¹O₂) can be also generated during persulfate activation via CuO. However, the issues regarding particles aggregation and metal leaching from the catalysts during the decontamination process remain to be addressed, which could have a remarkable impact on the catalytic degradation of organic pollutants. Accordingly in the present study, a novel biochar-supported bimetallic Fe₃O₄-CuO catalyst (CuFeBC) was facilely developed to activate peroxodisulfate (PDS) for the degradation of norfloxacin (NOR) in aqueous solution. The results showed CuFeBC has a superior stability against metal ions Cu/Fe leaching, and NOR (30 mg L^-1) was degraded at 94.5% within 180 min in the presence of CuFeBC (0.5 g L^-1) and PDS (6 mM) in pH 8.5. The scavenging of reactive oxygen species and electron spin resonance analysis revealed that ¹O₂ dominated the degradation of NOR. Compared with pristine CuO-Fe₃O₄, the interaction between biochar substrate and metal particles could significantly enhance the contribution of the nonradical pathway to NOR degradation from 49.6% to 84.7%. Biochar substrate could efficiently reduce the leaching of metal species from the catalyst, thereby maintaining excellent catalytic activity and lasting reusability of the catalyst. These findings could enlighten new insights into fine-tuning radical/nonradical processes from CuO-based catalysts for the efficient remediation of organic contaminants in polluted water.

The modified properties of sludge-based biochar with ferric sulfate and its effectiveness in promoting carbon release from particulate organic matter in rural household wastewater

The scarcity of carbon sources presents a significant challenge for the bio-treatment of rural domestic wastewater (RDW). This paper presented an innovative approach to address this issue by investigating the supplementary carbon source through in-situ degradation of particulate organic matter (POM) facilitated by ferric sulfate modified sludge-based biochar (SBC). To prepare SBC, five different contents of ferric sulfate (0%, 10%, 20%, 25%, and 33.3%) were added to sewage sludge. The results revealed that the pore and surface of SBC were enhanced, providing active sites and functional groups to accelerate the biodegradation of protein and polysaccharide. During the 8-day hydrolysis period, the concentration of soluble chemical oxidation demand (SCOD) increased and peaked (1087-1156 mg L^-1) on the fourth day. The C/N ratio increased from 3.50 (control) to 5.39 (25% ferric sulfate). POM was degraded the five dominant phyla, which were Actinobacteriota, Firmicutes, Synergistota, Proteobacteria, and Bacteroidetes. Although the relative abundance of dominant phyla changed, the metabolic pathway remained unchanged. The leachate of SBC (<20% ferric sulfate) was beneficial for microbes, but an excessive amount of ferric sulfate (33.3% ferric sulfate) could have inhibition effects on bacteria. In conclusion, ferric sulfate modified SBC holds the potential for the carbon degradation of POM in RDW, and further improvements should be made in future studies.

One-step synthesis of Bi2O2CO3/Bi2S3 S-scheme heterostructure with enhanced photoactivity towards dibutyl phthalate degradation under visible light

Bi₂O₂CO₃/Bi₂S₃ heterojunction was prepared by one-step hydrothermal method, where Bi(NO₃)₃ was employed as Bi source, Na₂S was used as a sulfur source, and CO(NH₂)₂ was adopted as C source. The load of Bi₂S₃ was adjusted by changing the content of Na₂S. The prepared Bi₂O₂CO₃/Bi₂S₃ illustrated strong photocatalytic activity towards dibutyl phthalate (DBP) degradation. The degradation rate was 73.6% under the irradiation of visible light for 3 h, which were 3.5 and 1.87 times for Bi₂O₂CO₃ and Bi₂S₃, respectively. In addition, the mechanism for the enhanced photoactivity was investigated. After combined with Bi₂S₃, the formed heterojunction structure inhibited the recombination of photogenerated electron-hole pair, improved the visible light adsorption, and accelerated the migration rate of the photogenerated electron. As a result, analysis of the radical formation and the energy band structure revealed that Bi₂O₂CO₃/Bi₂S₃ was consistent with the S-scheme heterojunction model. The S-scheme heterojunction allowed the Bi₂O₂CO₃/Bi₂S₃ to possess high photocatalytic activity. The prepared photocatalyst presented acceptable cycle application stability. This work not only develops a facile one-step synthesis technique for Bi₂O₂CO₃/Bi₂S₃, and also provides a good platform for the degradation of DBP.

Phthalate esters: occurrence, toxicity, bioremediation, and advanced oxidation processes

Phthalic acid esters are emerging pollutants, commonly used as plasticizers that are categorized as hazardous endocrine-disrupting chemicals (EDCs). A rise in anthropogenic activities leads to an increase in phthalate concentration in the environment which leads to various adverse environmental effects and health issues in humans and other aquatic organisms. This paper gives an overview of the research related to phthalate ester contamination and degradation methods by conducting a bibliometric analysis with VOS Viewer. Ecotoxicity analysis requires an understanding of the current status of phthalate pollution, health impacts, exposure routes, and their sources. This review covers five toxic phthalates, occurrences in the aquatic environment, toxicity studies, biodegradation studies, and degradation pathways. It highlights the various advanced oxidation processes like photocatalysis, Fenton processes, ozonation, sonolysis, and modified AOPs used for phthalate removal from the environment.

Combination of zero-valent aluminum-acid system and electrochemically activated persulfate oxidation for biologically pre-treated leachate nanofiltration concentrate treatment

This study investigated the performance of combined zero-valent aluminum (ZVAl) and electrochemically activated persulfate (PS) oxidation for the leachate nanofiltration concentrate (NFC) treatment. Firstly, operating parameters in the ZVAl procedure were optimized and under the optimum conditions (ZVAl dose 1 g/L, initial pH 1.5) the removal efficiency of the chemical oxygen demand (COD), UV₂₅₄, and color were 22.39%, 29.03%, and 48.26%, respectively. Secondly, the effect of various anode types (Ti/RuO₂, Ti/IrO₂, and Ti/SnO₂) within the electrooxidation (EO) process was evaluated. The Ti/RuO₂ anode was found to be the most effective one in terms of pollutant removal efficiencies and operation cost. The efficiency of single, binary, and hybrid processes was evaluated by control experiments and the results were ranked as PS < ZVAl < ZVAl + PS < EO < EO + PS < EO + ZVAl < EO + ZVAl + PS. In the following part of the study, the Box-Behnken design was preferred to optimize the operating parameters of the hybrid EO + ZVAl + PS process. The COD, UV₂₅₄, and color removal efficiencies under optimum conditions (4.88 mM PS dose, 1.6 A current applied, and 120 min reaction time) were 62.1%, 75.2%, and 99.9%, respectively. The estimated and experimentally obtained data were close to each other. The pollutant removal efficiencies increased in parallel with the current density and reaction time; however, the effect of the PS dose remained at a negligible level. The obtained results indicate the effectiveness of the hybrid EO + ZVAl + PS process for the treatment of leachate nanofiltration concentrate under optimized conditions.

Efficient peroxymonosulfate activation by biochar-based nanohybrids for the degradation of pharmaceutical and personal care products in aquatic environments

Recently, pharmaceutical and personal care products (PPCPs) have been of wide concern due to their ecological toxicity, persistence, and ubiquity in aquatic environments. Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have shown great potential for eliminating PPCPs due to their superior oxidation ability and adaptability. Biochar-based nanohybrids have been employed as emerging catalysts for peroxymonosulfate (PMS) activation. Until now, few researchers have summarized PMS activation by biochar-based catalysts for PPCPs removal. In this review, the types, sources, fates, and ecological toxicities of PPCPs were first summarized. Furthermore, various preparation and modification methods of biochar-based catalysts were systematically introduced. Importantly, the application of activating PMS with biochar-based multifunctional nanocomposites for eliminating PPCPs was reviewed. The influencing factors, such as catalysts dosage, PMS dosage, solution pH, temperature, anions, natural organic matters (NOMs), and pollutants concentration were broadly discussed. Biochar-based catalysts can act as electron donors, electron acceptors, and electron shuttles to activate PMS for the removal of PPCPs through radical pathways or/and non-radical pathways. The degradation mechanisms of PPCPs are correlated with persistent free radicals (PFRs), metal species, defective sites, graphitized degree, functional groups, electronic attributes, and the hybridization modes of biochar-based catalysts. Finally, the current problems and further research directions on the industrial application of biochar-based nanocomposites were proposed. This study provides some enlightenment for the efficient removal of PPCPs with biochar-based catalysts in PMS-AOPs.

Enhanced dewaterability of lake dredged sediments by electrochemical oxidation of peroxydisulfate on BDD anode

Dredged sediments, as a product of mitigating endogenous pollution of rivers and lakes, cause severe environmental pollution without suitable disposal. To reduce dredged sediments, the electrochemical oxidation (EO) of peroxydisulfate (PS) on a boron-doped diamond (BDD) anode (EO/BDD-PS) was utilized to enhance the dewaterability of the dredged sediments. The soluble chemical oxygen demand increased in the EO/BDD-PS system, and more than 70.0% of the specific resistance to filtration was reduced by EO/BDD-PS within 20 min. The optimal conditions were determined to be as follows: current density, 30 mA cm^-2; PS dosage 4 g L^-1; and initial pH, 6.96. After treatment with EO/BDD-PS, the electronegativity of the sludge flocs was alleviated and the particle size increased from 7.61 to 10.64 μm. Furthermore, proteins and polysaccharides were degraded, and tightly bound extracellular polymeric substances (TB-EPS) and loosely bound EPS (LB-EPS) were effectively transported to soluble EPS (S-EPS). Furthermore, humification of organic matter occurred in S-EPS and LB-EPS when the dredged sediment was treated with EO/BDD-PS. Dominant hydroxyl radicals (•OH) and sulfate radicals (SO₄•^-) were generated in the EO/BDD-PS system. Moreover, the efficiency of the filtrate as an electrolyte decreased slightly after recycling five times. Therefore, this method may be economical for enhancing the dewaterability of dredged sediments.

Investigating associations between urinary phthalate metabolite concentrations and chronic diarrhea: findings from the National Health and Nutrition Examination Survey, 2005-2010

This study aimed to explore the relationship between chronic diarrhea and urinary phthalate metabolite concentrations in US adults from the 2005-2010 NHANES study. After adjusting for potential confounding factors, logistic regression was used to explore the relationship between phthalates (PAEs) concentrations and chronic diarrhea, Bayesian kernel machine regression (BKMR), and quantile g calculation (quantile-based g calculation, qgcomp) which was used to study the combined and independent effects of PAEs on gastrointestinal infections. In the current study, 4260 adult participants over the age of 20 from the NHANES study were included, of whom 542 (12.72%) were assessed as having chronic diarrhea. In multivariate logistic regression analysis, after adjusting for all relevant covariates, the results showed that urinary phthalate metabolite concentrations were significantly associated with the risk of chronic diarrhea (P<0.001). Various PAEs were risk factors for chronic diarrhea, among which MiBP (OR=1.419, 95% CI: 1.416-1.423) and MCPP (OR=1.237, 95% CI: 1.235-1.239) were more significant. The BKME results showed a significant increase in the risk of chronic diarrhea with increasing total levels of the PAEs mixture. Mixed exposure to PAEs can promote the occurrence of chronic diarrhea, and the effect was more pronounced in obese people. Notably, most PAEs showed some degree of protection in overweight people. The risk effect of PAEs was more significant in the middle-aged and older population than in the younger population.

Optimization of PNP Degradation by UV-Activated Granular Activated Carbon Supported Nano-Zero-Valent-Iron-Cobalt Activated Persulfate by Response Surface Method

Nitrophenols are toxic substances that present humans and animals with the risk of deformities, mutations, or cancer when ingested or inhaled. Traditional water treatment technologies have high costs and low p-nitrophenol (PNP) removal efficiency. Therefore, an ultraviolet (UV)-activated granular activated carbon supported nano-zero-valent-iron-cobalt (Co-nZVI/GAC) activated persulfate (PS) system was constructed to efficiently degrade PNP with Co-nZVI/GAC dosage, PS concentration, UV power, and pH as dependent variables and PNP removal rate as response values. A mathematical model between the factors and response values was developed using a central composite design (CCD) model. The model-fitting results showed that the PNP degradation rate was 96.7%, close to the predicted value of 98.05 when validation tests were performed under Co-nZVI/GAC injection conditions of 0.827 g/L, PS concentration of 3.811 mmol/L, UV power of 39.496 W, and pH of 2.838. This study demonstrates the feasibility of the response surface methodology for optimizing the UV-activated Co-nZVI/GAC-activated PS degradation of PNP.

Surface facet Fe2O3-based visible light photocatalytic activation of persulfate for the removal of RR120 dye: nonlinear modeling and optimization

Photocatalytic activation of persulfate (PS) is recently emerged as an energy-efficient and environmentally sustainable approach for pollutants degradation, which enables to leverage the strengths of low-cost solar energy and heterogeneous catalysis. Herein, we investigated the photocatalytic decomposition of reactive red 120 (RR120) dye using PS-activated Fe₂O₃ nanoparticles and elucidated the effect of their facets, α-Fe₂O₃ (001), β-Fe₂O₃ (100), and γ-Fe₂O₃ (111). β-Fe₂O₃ not only boosted the charge carrier separation but also provided more active sites for PS activation resulting in 6- and 3.5-fold higher photocatalytic activities compared to α-Fe₂O₃ and γ-Fe₂O₃, respectively. Response surface methodology and artificial neural network coupled with genetic algorithm models were utilized to optimize and foresee Fe₂O₃/PS system under visible light. Almost 100% color removal and 82% organic removal were observed under the optimum conditions at 20 mg/L RR120, 22 mg/L β-Fe₂O₃, 18 mg/L PS, and pH: 3. Scavenger test indicated that both sulfate and hydroxyl radicals are responsible for the observed RR120 removal. Although cell viability test indicated that cytotoxicity of wastewater is not significantly reduced after treatment. All the results proposed that β-Fe₂O₃/PS at relatively low doses has a great potential to decompose and mineralize recalcitrant dyes in wastewater under invisible light.

Efficacy and cytotoxicity of engineered ferromanganese-bearing sludge-derived biochar for percarbonate-induced phthalate ester degradation

Phthalate esters (PAEs) are a group of ubiquitous organic environmental contaminants. Engineered ferromanganese-bearing sludge-derived biochar (SDB), synthesized using one-step pyrolysis in the temperature range between 300 and 900 °C, was used to enable Fenton-like processes that decontaminated PAE-laden sediments. SDB was thoroughly characterized using scanning electron microscopyenergy-dispersive spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller surface area, thermogravimetric analysis, Raman spectroscopy, Fourier-transform infrared spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis. The maximum PAE degradation was remarkable at 90% in 12 h at pH 6.0 in the presence of 1.7 g L^-1 of SDB 900. The highly-effective PAE degradation was mainly attributed to the synergism between FeO_x and MnO_x, which strengthened the activation of percarbonate (PC) via electron transfer, hydroxy addition, and hydrogen abstraction through radical (HO•) and nonradical (¹O₂) oxidation mechanisms, thereby facilitating PAE catalytic degradation over SDB in real sediments, which clearly proved the efficacy of ferromanganese-bearing SDB and PC for the remediation of contaminated sediments. The cytotoxicity exhibited by human skin keratinocyte cells exposure to high SDB concentration (100-400 µg mL^-1) for 24-48 h was low indicating insignificant cellular toxicity and oxidative damages. This study provides a new strategy for freshwater sludge treatment and reutilization, which enables a water-cycle-based circular economy and waste-to-resource recycling.

Degradation of 17β-estradiol by UV/persulfate in different water samples

Sulfate radical (•SO₄^-)-based advanced oxidation processes are widely used for wastewater treatment. This study explored the potential use of UV/persulfate (UV/PS) system for the degradation of 17β-estradiol (E2). The pH of the reaction system can affect the degradation rate of E2 by UV/PS and the optimum pH was 7.0; Br^- and Cl^- in water can promote the degradation rate, HCO₃^- has an inhibitory effect on the reaction, SO₄^2- and cations (Na⁺, Mg²⁺, K⁺) have no effect on the degradation rate. The degradation of E2 by UV/PS was a mineralization process, with the mineralization rate reaching 90.97% at 8 h. E2 in the UV/PS system was mainly degraded by hydroxylation, deoxygenation, and hydrogenation. E2 reaction sites were mainly located on benzene rings, mainly carbonylation on quinary rings, and bond breakage between C10 and C5 resulted in the removal of benzene rings and carboxyl at C2 and C3 sites. In the presence of halogen ions, halogenated disinfection by-products were not formed in the degradation process of E2 by UV/PS. E2 in the UV/PS system could inhibit the formation of bromate. The results of this study suggest that UV/PS is a safe and reliable method to degrade E2.