Investigate the multipath erasure of nitrobenzene over nanoscale zero-valent-iron/N-doped biochar hybrid with extraordinary reduction performance.

In this study, the facile carbothermal reduction method was enforced using urea as dopant to modify the structure and chemical composition of nanoscale zero-valent-iron/biochar hybrid thereby boosting its reduction performance. Through fine-tuning the N-doped amount, the optimal nZVI/N-doped BC was obtained, which exhibited more active sites (nZVI, persistent free radicals (PFRs), pyrrolic-N) and superior electrochemical conductivity. With these blessings, the electrons originating from galvanic cell reaction could zip along the highway within the hybrid. Taking nitrobenzene (NB) as the target pollutant, the quantitative analysis revealed that the NB reduction and adsorption removal efficiency were dramatically improved by 2.42 and 2.78 times, respectively. What's more, combining the in-situ experimental detection and theoretical calculations, unexpected NB reductive multipath with respect to PFRs and pyrrolic-N accelerating the Fe3+/Fe2+ cycle within the nZVI/N-doped BC system was decoded. The enhancement of Fe3+/Fe2+ cycle improved the electron utilization efficiency and maintained the reduction reactivity of the hybrid. This work raised awareness of the mechanisms regarding the reduction performance of nZVI/N-doped BC elevated by N-doped and the pollutant reductive pathway within the system, uncovered the dusty roles of PFRs and N-species during the reduction process.

Coupling sludge-based biochar and electrolysis for conditioning and dewatering of sewage sludge: Effect of char properties.

The addition of sludge-based biochar during electrochemical pretreatment of sewage sludge, as an efficient hybrid technology, is potentially to be applied in sludge deep-dewatering. The chars functioned as conductors, catalysts and skeleton particles could enhance the sludge dewaterability and increase the calorific value of the dewatered sludge cake. However, the effect of synthesis conditions on the char properties and further on the dewatering performance is still unknown. Herein, the sludge-based particle electrodes (SPEs) under three main synthesis conditions, including liquid-solid ratio, pyrolysis temperature and time, were prepared. The sludge-based biochars (i.e., SPE-400, SPE-600, and SPE-800 pyrolyzed under 400, 600 and 800 °C, respectively) were characterized and utilized as three-dimensional electrodes during sludge electrolysis. The increased pyrolysis temperature (within 400-800 °C) resulted in the enrichment of metallic ions and increment of specific surface area and pore volume of SPE, which led to the increased catalysis and adsorption sites for viscous proteins (PNs). Particularly, the pores of SPE-800 provided more drainage channels as skeleton builders. Compared with raw sludge, the capillary suction time (CST) and the specific resistance of filtration (SRF) of the treated sludge with 3D-SPE-800 were reduced by 58.12% and 81.01%, respectively, but the net sludge solids yield (YN) was increased by 87.05%. The highest decrease of hydrophilic α-Helix content in PNs (from 9.93% to 7.30%) was observed when using SPE-800 as particle electrode, revealing the crucial role of char characteristics on protein reduction and subsequent dewatering enhancement. The synergistic effects of electrolysis and sludge-based biochar provided a new insight for a closed-loop pretreatment of sewage sludge in the wastewater treatment plant.

High-Pressure Homogenization Pretreatment before Enzymolysis of Soy Protein Isolate: the Effect of Pressure Level on Aggregation and Structural Conformations of the Protein.

The high-pressure homogenization (HPH) treatment of soybean protein isolate (SPI) before enzymatic hydrolysis using bromelain was investigated. Homogenization pressure and cycle effects were evaluated on the enzymatic degree of hydrolysis and the antioxidant activity of the hydrolysates generated. The antioxidant activity of SPI hydrolysates was analyzed by 1,1-dipheny-2-picrylhydrazyl (DPPH). The sizes and structures of the SPI-soluble aggregate after HPH treatment were analyzed using dynamic and static laser light scattering. The changes in the secondary structure, as measured by Fourier transform infrared spectroscopy (FTIR) and the macromorphology of SPI, were measured by scanning electron microscope (SEM). These results suggested that the HPH treatment (66.65%) could increase the antioxidant activities of the SPI hydrolysates compared with the control (54.18%). SPI hydrolysates treated at 20 MPa for four cycles obtained higher DPPH radical-scavenging activity than other samples. The control was predicted to be a hard sphere, and SPI treatment at 10 MPa was speculated to be Gaussian coil, polydisperse, and then the high-pressure treated SPI became a hollow sphere. Changes in the secondary structures showed protein aggregate formation and rearrangements. The image of SPI varied from a globular to a clump structure, as observed by the SEM. In conclusion, combining HPH treatment and enzymolysis could be an effective way to improve the antioxidant activity of the SPI.

Comparison of cell rupturing by ozonation and ultrasonication for algal lipid extraction from Chlorella vulgaris.

Cell disruption is essential for lipid collection from cultivated microalgae. This study examines the performance of ultrasonication (US), conventional bubbling ozonation (CBO), and pressure-assisted ozonation (PAO) as a cell rupturing technique to obtain algal lipid from a freshwater unicellular microalgae Chlorella vulgaris, which was grown in BG11 medium at a temperature of 25 degrees C and illuminated by artificial lighting with light/dark cycle of 12 h/12 h. Changes in total organic carbon, total nitrogen, total phosphorous, and chlorophyll contents in the algae suspension after ozonation and US treatments were measured to evaluate the effectiveness of cell rupture by these techniques. Lipid yields of 21 and 27 g/100 g biomass were obtained using US and PAO, respectively. Lipid yields of about 5 g/100 g biomass were obtained using CBO. In all rupturing treatments, C16 and C18 compounds were found to be predominant accounting for 90% of the fatty acids. Using US for rupturing, fatty acids of C 16:0, C18:1, and C18:2 were predominant, accounting for 76 +/- 4.2% of all the fatty acids. Using CBO and PAO involving ozone, fatty acids of C16:0 and C18:0 were predominant, accounting for 63-94% of the products. The results suggest that saturated fatty acid methyl ester (FAME) products are predominant with oxidative ozonation rupturing while unsaturated FAME products of lower-melting points predominant with physical ultrasonic rupturing means. PAO was an effective cell rupture method for biodiesel production with high lipid yield and more saturated hydrocarbon products.

FeS combined ozonation to remove p-aminobenzenesulfonamide from water: Density functional theory insights into the mechanism.

The applicability and performance of FeS in ozonation process to remove p-aminobenzenesulfonamide (SN) from water was assessed, and the working mechanism of FeS was comprehensively explored by both experimental means and density functional theory (DFT) simulation. FeS combined ozonation achieved 74% of SN removal in 60 min under the optimal condition, which was 37% higher than by ozonation alone, and 12% higher than FeO combined ozonation. Highly active species of •OH, •SO4-, 1O2 and •O2- were detected in the FeS combined ozonation system, the evolution pathway of the involved species was expounded with the aid of DFT calculation. The results revealed that •O2-, H2O2 and SO42- were originally formed via interface reactions on FeS surface, then gradually transformed into •OH, 1O2 and •SO4- through subsequent chain reactions. Moreover, FeS had a lower energy barrier of 0.16 eV than FeO with a value of 0.83 eV for the transformation of ozone to active atomic oxygen. The presented study provided a significant insight into the role of Fe-based materials in ozonation, and was of great importance to guide the route for ozonation process improvement.

Utilization of porous carbon synthesized with textile wastes via calcium acetate template for tetracycline removal: The role of template agent and the formation mechanism.

A porous carbon obtained from cotton/polyester textile wastes was synthesized by the calcium acetate template method. This research studied the effect of preparation conditions and evaluated the characterization of porous carbon, and further explored its formation mechanism. The porous carbon possessed a high specific surface area of 1106.63 m2/g under an optimum condition (pyrolysis temperature = 800 °C, mass ratio of CA: CPW = 1.5:1, pyrolysis time = 1.5 h). It was found that calcium acetate played the role of catalyst to promote the degradation of cotton/polyester textile. CaCO3 and CaO fabricated by calcium acetate acted as the template to generate a mesoporous structure. The generated CO2 etched carbon skeleton to create a large number of micropores. Besides, it was supported as the carbon source to fuse with carbon structures, further consolidating the aromatic structures of porous carbon. The optimized porous carbon has a high adsorption capacity of 506.40 mg/g for tetracycline. And the adsorption data fitted better by the first-pseudo-order model and Langmuir isotherms with an endothermic and spontaneous adsorption process. The cotton/polyester-based porous carbon was a promising economical material for tetracycline.

New insights into iron/nickel-carbon ternary micro-electrolysis toward 4-nitrochlorobenzene removal: Enhancing reduction and unveiling removal mechanisms.

The ternary micro-electrolysis material iron/nickel-carbon (Fe/Ni-AC) with enhanced reducibility was constructed by introducing the trace transition metal Ni based on the iron/carbon (Fe/AC) system and used for the removal of 4-nitrochlorobenzene (4-NCB) in solution. The composition and structures of the Fe/Ni-AC were analyzed by various characterizations to estimate its feasibility as reductants for pollutants. The removal efficiency of 4-NCB by Fe/Ni-AC was considerably greater than that of Fe/AC and iron/nickel (Fe/Ni) binary systems. This was mainly due to the enhanced reducibility of 4-NCB by the synergism between anode and double-cathode in the ternary micro-electrolysis system (MES). In the Fe/Ni-AC ternary MES, zero-iron (Fe0) served as anode involved in the formation of galvanic couples with activated carbon (AC) and zero-nickel (Ni0), respectively, where AC and Ni0 functioned as double-cathode, thereby promoting the electron transfer and the corrosion of Fe0. The cathodic and catalytic effects of Ni0 that existed simultaneously could not only facilitate the corrosion of Fe0 but also catalyze H2 to form active hydrogen (H*), which was responsible for 4-NCB transformation. Besides, AC acted as a supporter which could offer the reaction interface for in-situ reduction, and at the same time provide interconnection space for electrons and H2 to transfer from Fe0 to the surface of Ni0. The results suggest that a double-cathode of Ni0 and AC could drive much more electrons, Fe2+ and H*, thus serving as effective reductants for 4-NCB reduction.

Fabrication of porous carbon derived from cotton/polyester waste mixed with oyster shells: Pore-forming process and application for tetracycline removal.

Porous carbon was fabricated from cotton/polyester-based textile wastes as a carbon source coupled with oyster shells for tetracycline removal. The preparation conditions were optimized and detailed characterization was conducted to study the effects of oyster shells on cotton/polyester pyrolysis. The optimal pyrolysis temperature (900 °C), pyrolysis time (1 h) and mass ratio (OS/CPW of 1:1) were determined using the Box-Behnken experiment. The best porous carbon reached a surface area of 645.05 m2/g. Oyster shells acted as templates to produce cotton/polyester-based porous carbon and a possible pore-forming process was proposed. CaO was converted from CaCO3, which played the dominant role in developing the mesoporous structure. CO2 gas released from CaCO3 promoted the creation of micropore structure. In addition, the impurites of oyster shells acted as the dispersing agent inhibiting CaCO3 and CaO aggregation and growth. Fe2O3 and K2O from impurities reacted with the carbon skeleton to increase microporosity. Finally, the well-developed and uniform porous carbon was obtained. The first-pseudo order model and Langmuir isotherms were suitable. The maximum adsorption capacity of PC-OS-900 was 515.17 mg/g which competed with other waste-based adsorbents. The TET adsorption mechanism was related to pore distribution, hydrogen bonds, π-π EDA interactions and electrostatic interactions.

Ozonation catalysed by ferrosilicon for the degradation of ibuprofen in water.

The search for optimal catalysts to improve the working efficiency of ozonation has always been an important issue in the research field of advanced oxidation processes. In this study, a novel catalyst, ferrosilicon, was selected as the catalyst in heterogeneous catalytic ozonation to degrade ibuprofen (IBP) in water and treat real pharmaceutical wastewater. During the procedure, 45#ferrosilicon exhibited the best catalytic activity. Under the optimized experimental conditions, the IBP removal reached 75%, which was a great improvement compared to the 37% removal by ozone alone. The 45#-ferrosilicon-catalysed ozonation also achieved 68% TOC removal for real pharmaceutical wastewater, which was 31% higher than that by ozone alone. The degradation pathway of IBP was proposed using GC/MS. The EPR test proved that the main active species in the system were free active radicals •OH, and the measured accumulative •OH amount was 102 µmol. The characterization results show that the nascent metallic oxides, hydroxides, and hydroxyoxides on the ferrosilicon surface facilitated the decomposition of ozone molecules and generation of free active radicals. The removal of target organic contaminants in the water was mainly attributed to the oxidization of these highly active species.

Conversion of cotton textile waste to clean solid fuel via surfactant-assisted hydrothermal carbonization: Mechanisms and combustion behaviors.

The cotton textile was an abundant energy resource while was otherwise treated as waste. In this work, surfactants were used as catalysts in the hydrothermal carbonization (HTC) to transform cotton textile waste (CTW) into clean solid fuel. Furthermore, the conversion mechanisms of hydrothermal products during surfactant-assisted HTC were preliminarily proposed. The results showed that Span 80 and sodium dodecylbenzenesulfonate facilitated the transformation of CTW into bio-oil, while Tween 80 was more conducive to the development of pseudo-lignin, which endowed hydrochars higher energy density and updated the fuel quality and combustion behavior. Therefore, the research presented an effective method to convert CTW to clean solid fuel through the HTC treatment combining with surfactants.

Understanding reactions and pore-forming mechanisms between waste cotton woven and FeCl3 during the synthesis of magnetic activated carbon.

FeCl3 is a valuable iron salt used in the synthesis of magnetic waste cotton woven-based activated carbon. Although it has received extensive research attention, more information is required regarding its interactions with the carbon matrix. This systematic study describes the potential reactions of FeCl3 and waste cotton woven. First, the textural properties of waste cotton woven-based activated carbon synthesized under various conditions were investigated via element analysis, N2 sorption/desorption isotherms, and scanning electron microscopy. Then, the possible reaction mechanisms were deduced through various characterization methods. The results demonstrate that FeCl3 can lower the initial decomposition temperature of WCW to 135 °C and catalyze decarboxylation and decarbonylation at 100-330 °C to elevate the formation of microporous structures. Moreover, FeCl3 can also form Lewis acid sites at 330-700 °C and promote the cross-linking reaction to develop intricate microporous structures and carbonaceous materials with the synergistic effect of Fe3+ and Cl-. FeCl3 could be used as a template-like agent to form mesoporous structures. Meanwhile, it can also act as a magnetizer that Fe3O4 derived from the decomposition of FeCl3 would insert into the carbon matrix and combine with C-Cl to tailor the magnetic controllable activated carbon. Finally, we confirmed that extending the activation time could convert the structure of waste cotton woven-based activated carbon and increase the number of active sites, thereby further improving the catalytic properties of FeCl3 in pore formation.

Effect of dispersant on the synthesis of cotton textile waste-based activated carbon by FeCl2 activation: characterization and adsorption properties.

Considering the accumulation and high consumption of activating agents, anhydrous ethanol (AE) could be used to dissolve them to improve the dispersion effect, which was an effective way of improving the practical utilization rate. In this study, FeCl2 was dissolved in AE and further impregnated cotton textile waste (CTW) to prepare activated carbons (ACs) by pyrolysis. Afterward, ACs prepared in optimal conditions determined by the orthogonal experiment evaluated the physicochemical properties and adsorption capacities for Cr(VI). The results illustrated that AE greatly increased the dispersion of FeCl2 on CTW, reduced the conventional impregnation dosage, and remarkably improved the activation efficiency. Textural analyses revealed that ACs exhibited excellent porosity properties and graphite carbon structure. FeCl2 catalyzed the decomposition of volatile substances to produce gaseous products and promoted the transformation of amorphous carbon to graphite carbon that was conducive to pore development, followed by the formation of developed micropores and crystal structures. The adsorption performance of ACs was estimated using Cr(VI), and the adsorption was fitted with the pseudo-second-order kinetic and the Langmuir isotherm. Furthermore, the ACs possessed superior magnetization and reusability. Graphical abstract.

Activation of grapefruit derived biochar by its peel extracts and its performance for tetracycline removal.

A novel adsorbent derived from grapefruit peel (GP) based biochar (GPBC) was synthesized by combined carbonization of GP and subsequent activation by GP extracts. Compared to biochar without extracts activation, the technique granted GPBC-20 (with 1:20 of solid-solution ratio) more abundant surface functional groups, which exerts the adsorbent superior performance for tetracycline (TC) adsorption (37.92 mg/g v.s. 16.64 mg/g). The adsorption kinetics, isotherms and thermodynamics models were further used to evaluate the adsorption behavior of GPBC. The enhanced adsorption was analyzed by characterization of fresh and used GPBC, revealing that the adsorption mechanism was comprised of pore filling, charge interaction and chemical bonding. The comprehensive investigation of using agricultural waste extracts as activator to prepare its raw materials-based adsorbents may be of great significance for enhanced resource utilization.

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.

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.

The rainfall effect onto solidification and stabilization of heavy metal-polluted sediments.

Rainfall makes impacts on the process of solidification/stabilization (S/S) and the long-term safety of solidified matrix. In this study, the effect of rainfall on solidification/stabilization process was investigated by the rainfall test. The unconfined compressive strength (UCS) and toxicity characteristic leaching procedure (TCLP) were adopted to characterize the properties of S/S sediments before and after the rainfall test. The samples cured for 28 days were selected for semi-dynamic leaching tests with a simulated acidic leachant prepared at pH of 2.0, 4.0 and 7.0. The effectiveness of S/S treatment was evaluated by diffusion coefficient (De ) and leachability index (LX). The results indicated that UCS decreased at maximum deterioration rate of 34.23% after 7 days of curing, along with the minimum rate of 7.98% after 28 days by rainfall, with greater than 14 days referred. The rainfall had little effect on the leaching characteristics of heavy metals during the curing process. However, the simulated acid rain made significant impacts on the leaching behaviours of the heavy metals in the S/S materials. All the values of cumulative fraction of leached heavy metals were less than 2.0%, exhibition of good stabilization of cement. Furthermore, the calculated diffusion coefficient (De ) for Cu was 1.28 × 101 cm2 s-1, indicating its low mobility of heavy metal ions in S/S sediments. Furthermore, the calculated diffusion coefficients (Di ) for Cd, Cu and Pb were 7.44 × 10-11, 8.18 × 10-12 and 7.85 × 10-12 cm2 s-1, respectively, indicating their relatively low mobility of heavy metal in S/S sediments.

Synthesis of char-based adsorbents from cotton textile waste assisted by iron salts at low pyrolysis temperature for Cr(VI) removal.

Char-based adsorbents (char-FeCl3, char-FeCl2, and char-FeCit) derived from cotton textile waste (CTW) were synthesized by one-step low-temperature pyrolysis approach with different iron salts. The properties of the samples were conducted by BET, SEM, EDS, XRD, XPS, TEM, and FTIR. The results suggested that the surface areas of char-FeCl3 and char-FeCl2 were higher than those of char-FeCit. The presence of Fe2O3 as well as pyrolysis gas (HCl (g) and H2O (g)) could catalyze the formation of porosity. Meanwhile, FeCl3 showed the strongest catalysis effect to decompose cellulose to produce char. The pyrolysis process analysis was investigated by means of thermogravimetry-DSC. FeCl3 and FeCl2 could accelerate the breakage of cellulose structure whereas FeC6H5O7 was not beneficial to form char at low temperature as the incomplete decomposition of citrate. The adsorption property of Cr(VI) for the chars was evaluated. Adsorption processes were fitted well with the Freundlich model, and char-FeCl3 presented the best adsorptive capacity (70.39 mg/g). Thus, this low-temperature pyrolysis method was economical and technologically simplified as well as efficient adsorption capacity of Cr(VI) removal. Graphical abstract.

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

The degradation of organic contaminants in actual textile wastewater was carried out by iron carbon (Fe-C) micro-electrolysis. Different Fe-C micro-electrolysis systems (SIPA and SISA) were established by using scrap iron particle (SIP) and scrap iron shaving (SIS) as anode materials. The optimal condition of both systems was obtained at the initial pH of 3.0, dosage of 30 g/L and Fe/C mass ratio of 1:1. Commercial spherical Fe-C micro-electrolysis material (SFC) was used for comparison under the same condition. The results indicated that total organic carbon (TOC) and chroma removal efficiencies of SIPA and SISA were superior to that of SFC. Total iron concentration in solution and XRD analysis of electrode materials revealed that the former showed relatively high iron corrosion intensity and the physicochemical properties of scrap iron indeed affected the treatment capability. The UV-vis and 3DEEM analysis suggested that the pollutants degradation was mainly attributed to the combination of reduction and oxidation. Furthermore, the potential degradation pathways of actual textile wastewater were illustrated through the GC-MS analysis. Massive dyes, aliphatic acids, and textile auxiliaries were effectively degraded, and the SIPA and SISA exhibited higher performance on the degradation of benzene ring and dechlorination than that by SFC. In addition, SIPA and SISA exhibited high stability and excellent reusability at low cost. Graphical abstract.

Preparation of Sludge-Derived Activated Carbon by Fenton Activation and the Adsorption of Eriochrome Black T.

Sludge-derived activated carbon (SAC) was prepared by Fenton activation and calcination, and used as adsorbent to eliminate Eriochrome Black T (EBT) dye from aqueous media. The characterization results indicated that the produced SAC had a porous structure, high specific surface area, and abundant functional groups on its surface. The adsorption process was affected by pH, adsorbent dosage, time, and temperature. The adsorption capacity increased with temperature, and the highest adsorption capacity reached 178.2 mg·g-1 in 48 h at 318 K and pH 6. The results of the adsorption isotherm, kinetic, and thermodynamic analyses revealed that the adsorption of EBT onto SAC was naturally endothermic and spontaneous, involved both physical and chemical processes, and belonged mostly to the multilayer type of adsorption.

Ni-Fe layered double hydroxides catalized ozonation of synthetic wastewater containing Bisphenol A and municipal secondary effluent.

Ni-Fe Layered Double Hydroxides (Ni-Fe LDHs) was prepared, characterized and used as catalyst in heterogeneous catalytic ozonation of Bisphenol A (BPA) and other organic compounds in secondary effluent. The characterization and ozonation results revealed that the Ni-Fe LDHs possessing a Ni: Fe ratio of 3:1 had the best crystalline and the highest affinity for ozone. Under the optimized conditions, the final TOC and COD removal achieved was 56% and 68%, respectively. BPA in the secondary effluent could be removed completely by Ni3-Fe LDH catalyzed ozonation. The organic compounds removal was mainly attributed to the oxidation by free active radicals such as hydroxyl radicals (OH). In this research the accumulative ·OH in the reaction system was determined to be 28.2 µmol at the reaction time of 60 min. The free active radicals were mostly generated through the electron transfer among different valences of metals on Ni-Fe LDHs surface, and subsequently diffused into bulk solution to oxidize the target organic compounds there.