Adsorption Catalytic Oxidation Research Articles

Enhanced effect of sonochemistry on the degradation of trace antibiotics in water by N-β-rGO/PMS adsorption-catalytic oxidation system

Sonochemistry was used to improve the degradation performance of trace antibiotics in water by the adsorption-catalytic oxidation system composed of Nitrogen-doped cyclodextrin reduced graphene oxide (N-β-rGO) and peroxymonosulfate (PMS). The results indicated that after loading ultrasound, >90% of antibiotics such as SMZ, LVX, CLI, TC, PEN, and CHL were removed within 10 min. Increasing the sound intensity, raising the system temperature, and increasing the initial PMS concentration all improved the strengthening effect. Among them, the removal rate was enhanced by >10% under low pH conditions. Moreover, the calculated enhancement factor of ultrasound enhancement was >1.30. The magnitude of the enhancement effect was correlated with the logP of antibiotics.

Oxygen-deficient layered ε-MnO2 nanosheets derived from acid-etched La3Mn2O7 for robust adsorption-catalytic oxidation of toluene

Manganese dioxide (MnO2) stands out as a promising catalyst for toluene degradation yet refining its synthesis for optimal efficiency poses a significant challenge. In this study, we presented an up-bottom synthesis approach for ε-MnO2 by selectively removing inactive La ions from La3Mn2O7 (LLM) through acid etching, yielding stacked nanosheets with enriched oxygen vacancies. The resulting H2SO4-LLM catalyst exhibited efficient synergistic adsorption-catalytic oxidation effects, attributed to its exceptional specific surface area (307.0 m2/g) and abundant acidic sites, achieving almost 90 % removal of 2000 mg/m3 toluene (T90) at 196 ℃ and complete oxidation to CO2 at 205 °C at a space velocity of 18000 mL/(g·h), outperforming most state-of-the-art catalysts for toluene removal. The study elucidates the role of lattice oxygen in catalyzing toluene oxidation and reveals the intricate interplay between oxygen adsorption, lattice oxygen mobility, and redox capability, paving the way for the development of robust catalysts for environmental remediation.

MOF-Derived Ni/ZIF-8/ZnO Arrays on Carbon Fiber Cloth for Efficient Adsorption-Catalytic Oxidation.

The catalytic oxidation of toxic organic pollutants in water requires enhanced efficiency for commercial applications. A ZnO nanorod array grown on a carbon fiber cloth (CFC) serves as the zinc source to ensure that the Ni/ZIF-8/ZnO nanoreactor is constructed. The Ni/ZIF-8/ZnO/CFC nanoreactor efficiently activates peroxymonosulfate (PMS) for bisphenol A (BPA) degradation owing to its high density of active sites, high adsorbability, and dispersibility structure, which concentrates catalytic and adsorptive sites within a confined space. Experimental and theoretical calculations clearly show that the introduction of Ni is beneficial for improving the adsorption of BPA and the activation of PMS. The synergistic mechanism of BPA adsorption-PMS activation is also investigated, and the degradation pathway of BPA is examined. Moreover, a filter catalytic unit is constructed using Ni/ZIF-8/ZnO/CFC to achieve a continuous zero discharge of BPA, which is convenient for nanocatalyst recycling. This study aims to develop a new strategy for the removal of emerging organic pollutants from water using a system with strong adsorption and catalytic capabilities.

Adsorption characteristics of N-rGO for multiple representative trace antibiotics in water.

Antibiotics have attracted considerable attention as pollutants; however, they have not been controlled because they cannot be effectively treated via conventional water treatment. In this study, nitrogen-doped reduced graphene oxide (N-rGO) was prepared, and its adsorption performance on multiple trace antibiotics in water was investigated by considering sulfamethoxazole, levofloxacin, clindamycin, tetracycline, penicillin, and chloramphenicol as target pollutants. The results demonstrated that the adsorption process was completed within 60min at a removal rate exceeding 80%. The adsorption process was in line with the first-order kinetic equation and the Langmuir isothermal adsorption model, with a theoretical maximum adsorption capacity of 1,265.82mg g-1 . Meanwhile, the effect of pH value was related to the structure of antibiotics. Simulation studies showed that anions and cations in natural water matrix did not inhibit the adsorption process, whereas humic acid adversely affected the adsorption effect. Characterizations revealed that the N-rGO surface was wrinkled with abundant and diverse oxygen-containing functional groups, which provided suitable conditions for efficient adsorption. The results indicated that N-rGO rapidly and effectively adsorbed trace antibiotics in water, thus providing a basis for constructing an adsorption-catalytic oxidation system. Overall, the proposed method is excellent for treating trace antibiotics in a water environment.

Adsorption-enforced Fenton-like process using activated carbon-supported iron oxychloride catalyst for wet scrubbing of airborne dichloroethane

Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H2O2 and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H2O2 concentrations. By pulsed or continuous dosing H2O2, the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control.

Simultaneous degradation of trace antibiotics in water by adsorption and catalytic oxidation induced by N-doped reduced graphene oxide (N-rGO): synergistic mechanism

Aimed at current difficulties in the treatment of trace antibiotics in water, an adsorption-catalytic oxidation system was established by combining persulfate and graphene, which have the dual functions of adsorption and catalysis, for simultaneous enrichment and degradation of trace antibiotics in water. The experimental results showed that over 90% sulfamethoxazole could be degraded by the proposed system. The activation energy of the proposed system was 7.9 kJ mol−1, which was significantly lower than those of typical Co catalysts and some carbon-based catalysts. Synergistic effect analysis revealed that catalytic oxidation was the key degradation kinetic of the proposed system, while adsorption showed a significant enhancement effect. Specifically, a compound with large adsorption capacity tended to be degraded preferably and rapidly. Characterization results indicated that N atoms were doped into the graphene framework, resulting in significant impacts on the activation process of potassium bisulfate by activating the sp2 C system. Quenching and free radical trapping experiments revealed that degradation catalyzed by the proposed system was a non-free radical oxidation reaction dominated by singlet oxygen. In summary, the proposed design was rational, N-rGO surface provided good adsorption and catalysis sites, the synergistic effect of adsorption and catalytic oxidation led to rapid and effective enrichment and in situ degradation of trace antibiotics in water.

A high-performance and stable Cu/Beta for adsorption-catalytic oxidation in-situ destruction of low concentration toluene

Finding a cost-effective treatment to remove of low concentrations of volatile organic compounds (VOCs) is still a challenge. In this study, a Cu/Beta material was developed for in situ adsorption-catalytic oxidation of low concentrations of toluene. The results showed that the addition of Cu enhanced the adsorption and catalytic oxidation of toluene by Beta zeolite. Cu7/Beta with a Cu+ ratio of close to 50% performed best. The high adsorption of Cu7/Beta was mainly attributed to the abundant Cu+ species and the micro-mesoporous structure of the Beta zeolite, and the high catalytic oxidation was attributed to the lattice oxygen in the uniformly dispersed CuO. Finally, the adsorption intermediates and reaction pathways in the catalytic oxidation of toluene were clarified using XPS and DRIFTS spectra. This work provides new strategies for the development of efficient and stable adsorption-catalytic oxidation in situ destruction materials.

Combining bi-functional Pt/USY and electromagnetic induction for rapid in-situ adsorption-combustion cycling of gaseous organic pollutant

By exploiting the superior adsorption capacity of ultra-stable Y-type zeolite (USY) and accurate input of energy by electromagnetic induction field (EMIF) technique, we successfully designed a highly energy-efficient system to eliminate gaseous toluene a common air pollutant. Pristine USY as adsorbent enriches gaseous toluene by a factor of fifteen, via room-temperature adsorption and then EMIF-driven thermal desorption. This operation model involving intermittent heating and mass transfer saves a lot of energy. Especially during temperature rising, 98.9% electric energy can be saved by the EMIF heating in comparison with conventional furnace approaches. In the bi-functional “adsorption-catalytic oxidation” 1Pt/USY, the concentrated toluene undergoes direct oxidation into CO2 rather than desorption when the EMIF heating starts, so one-step enrichment and mineralization are realized. In addition, the developed bi-functional system operates between adsorption and catalytic decomposition flexibly, which makes it ideal for cleaning VOCs emitted from intermittent sources.

One-step synthesis of ZnFe2O4-loaded biochar derived from leftover rice for high-performance H2S removal

• The RZF was synthesized via one-step carbonation activation of kitchen leftover rice. • ZnCl 2 and FeCl 3 were employed as both activator and precursor for preparing RZF. • The as-obtained RZF delivered outstanding desulfurization capacity and regeneration ability. • The postulated mechanisms of H 2 S removal on the RZF was proposed and verified. Hydrogen sulfide (H 2 S) is a major air pollutant posing a serious threat to the environment and public health. It is highly attractive to develop state-of-the-art adsorbent to remove H 2 S. Herein, a novel ZnFe 2 O 4 -loaded porous biochar (RZF) with a high surface area of 1065 m 2 /g was synthesized via one-step carbonation activation of kitchen leftover rice with ZnCl 2 and FeCl 3 as activators. The optimized RZF-500-1:1 was obtained by rationally adjusting the activation ratio (the mass ratio of leftover rice and ZnFe 2 O 4 ) and pyrolysis temperature. Such RZF-500-1:1 delivered high-performance H 2 S removal with the breakthrough capacity up to 228.29 mg/g at 25 °C, whilst the inactivated biochar (carbonization without activator) only showed a much lower adsorption capacity at circa 12.11 mg/g of H 2 S. The desulfurization conditions had a significant effect on the H 2 S breakthrough capacity, and the adsorbent exhibited better desulfurization performance at room temperature and in the presence of oxygen. The desulfurization mechanism on the ZnFe 2 O 4 -loaded biochar was proposed to be an adsorption-catalytic oxidation coupled process. Moreover, the as-fabricated sample showed high regeneration ability, retaining 91.6% of the initial breakthrough capacity after five regeneration cycles. This novel one-step preparation method would permit a gain of time and energy to obtain efficient activated carbons intended to capture H 2 S.

Development of Mn-Si-MEL as a bi-functional adsorption-catalytic oxidation material for VOCs elimination

Mn-Si-MEL zeolite was developed as a bi-functional adsorption-catalytic oxidation material for volatile organic compounds (VOCs) elimination due to its good hydrophobicity & good organophileproperty brought by the substitution of Mn for Al in zeolite and the superior catalytic oxidation property endowed by the existence of Mn species. Various Mn-Si-MEL samples were obtained by introducing Mn to MEL crystallization system via different ways. It was found the incorporated Mn ways have a significant effect on the behavior of Mn being involved in the crystallization of MEL and finally influenced the distribution of Mn in zeolite as well the physicochemical properties of product zeolite. The seeding method (Mn-S2(Seed)) is favorable for the good incorporation and uniform distribution of Mn in zeolite while both recrystallization method (Mn-S2(RC)) and direct synthesis method (Mn-S2(DH)) are favorable for obtaining more reducible Mn species and surface adsorbed oxygen species. The Mn amount incorporated into zeolite follows Mn-S2(RC) (1.96 wt%) > Mn-S2(Seed) (1.07 wt%) ≈ Mn-S2(DH) (0.97 wt%), the adsorption capacity of various samples follows Mn-S2(Seed) (83.3 μmol/g) ≈ Mn-S2(RC) (82.1 μmol/g) > Mn-S2(DH) (76.1 μmol/g), while the catalytic oxidation ability of three samples follows Mn-S2(RC) ≈ Mn-S2(DH) > Mn-S2(Seed). Furthermore, Mn-S2(RC) which exhibits both superior adsorption capacity and catalytic oxidation ability shows good hydrophobicity and superior recyclability, demonstrating its great potential to be applied in the VOCs elimination by an enrichment-degradation route.

The role of PAC adsorption-catalytic oxidation in the ultrafiltration performance for treating natural water: Efficiency improvement, fouling mitigation and mechanisms

Powdered activated carbon (PAC) has turned out to be an efficient adsorbent in drinking water treatment, whereas its application integrated with membrane filtration is still controversial because of the combined fouling effect between organic pollutants and PAC. To this end, an integrated process of combining PAC adsorption-catalytic oxidation and membrane filtration was proposed for natural surface water treatment. The synergistic effect of PAC and peroxymonosulfate (PMS) was confirmed through the generation of reactive oxidation species, and both radical oxidative pathways (•OH, SO4•− and O2•−) and nonradical (1O2 and PMS) pathways involved in the process. The removal efficiency of DOC and UV254 was significantly strengthened by PAC/PMS, with removal rates of 56.1% and 64.9%, respectively. The integration of PAC and PMS could significantly enhance the reduction of fluorescent organics, and pollutants with varying molecular weights. The fouling condition of membrane was dramatically alleviated, with the flux increased by 38.9%, and the reversible and irreversible resistances declined by 79.7% and 48.3%, respectively. The major fouling mechanism was significantly changed, and complete pore blocking always played a dominant role, rather than cake filtration. The effectiveness of PAC/PMS was further verified by the characterization of membrane surface morphologies and functional groups. Moreover, the attractive interactions between foulants and membrane were converted to repulsive interactions with the pretreatment of PAC/PMS. The proposed synergistic process was efficient and convenient, which could significantly improve the purification efficiency of conventional PAC-UF system in drinking water treatment.

Abatement of Toluene Using a Sequential Adsorption-Catalytic Oxidation Process: Comparative Study of Potential Adsorbent/Catalytic Materials

A novel strategy for toluene abatement was investigated using a sequential adsorption-regeneration process. Commercial Hopcalite (CuMn2Ox, Purelyst101MD), Ceria nanorods, and UiO-66-SO3H, a metal–organic framework (MOF), were selected for this study. Toluene was first adsorbed on the material and a mild thermal activation was performed afterwards in order to oxidize toluene into CO2 and H2O. The materials were characterized by XRD, N2 adsorption-desorption analysis, H2-TPR and TGA/DSC. The best dynamic toluene adsorption capacity was observed for UiO-66-SO3H due to its hierarchical porosity and high specific surface area. However, in terms of balance between storage and catalytic properties, Hopcalite stands out from others owing to its superior textural/chemical properties promoting irreversible toluene adsorption and outstanding redox properties, allowing a high activity and CO2 selectivity in toluene oxidation. The high conversion of toluene into CO2 which easily desorbs from the surface during heating treatment shows that the sequential adsorption-catalytic thermal oxidation can encompass a classical oxidation process in terms of efficiency, CO2 yield, and energy-cost saving, providing that the bifunctional material displays a good stability in repetitive working conditions.

Catalyst design of Pt/TiO2 microsphere for benzene oxidation under microwave irradiation

Pt/TiO2 microspheres with sea-urchin like structures were prepared by sequential processes including the preparation of TiO2 by a hydrothermal method and the preheating of the TiO2, the deposition of Pt nanoparticles on the TiO2 surface, followed by post heating in O2/N2 and H2. The TiO2 and Pt/TiO2 catalysts were characterized by XRD, Raman, SEM, TEM and N2 adsorption studies. The average diameter of TiO2 microspheres was about 250 nm. The TiO2 microspheres were composed of TiO2 nanoparticles with the size of 20−30 nm. Pt particles with the size of 3 nm were highly dispersed on the TiO2 microsphere by liquid phase adsorption of colloidal Pt particles. The heating of TiO2 at 300 °C before and after the Pt deposition did not change the size of TiO2 microsphere and reduced the surface area from 238 to 137 m2 g−1. The Pt/TiO2 microsphere exhibited higher catalytic activity for benzene oxidation than Pt/TiO2 P25 under normal outer heating, whereas pristine TiO2 exhibited almost no activity. Activated carbon was used as a catalyst with a mixture of Pt/TiO2 microspheres when performing the catalytic reaction under microwave heating. The mixture of Pt/TiO2 and activated carbon showed higher benzene oxidation activity under microwave irradiation than under normal external heating. The mixture was applied to benzene adsorption-catalytic oxidation combined processes.

Hierarchical porous HPW/titania–silica material with superior adsorption-catalytic oxidation activity for multi-ring thiophenic sulfur compounds

HPW/titania–silica catalysts with micro-meso-macroporous structures and high specific surface areas are prepared and applied as oxidative desulfurization catalysts.

Synergic mechanism of adsorption and metal-free catalysis for phenol degradation by N-doped graphene aerogel

3D porous N-doped reduced graphene oxide (N-rGO) aerogels were synthesized by a hydrothermal reduction of graphene oxide (GO) with urea and following freeze-drying process. N-rGO aerogels have a high BET surface of 499.70 m2/g and a high N doping content (5.93–7.46 at%) including three kinds of N (graphitic, pyridinic and pyrrolic). Their high catalytic performance for phenol oxidation in aqueous solution was investigated by catalytic activation of persulfate (PS). We have demonstrated that N-rGO aerogels are promising metal-free catalysts for phenol removal. Kinetics studies indicate that phenol degradation follows first-order reaction kinetics with the reaction rate constant of 0.16799 min−1 for N-rGO-A(1:30). Interestingly, the comparison of direct catalytic oxidation with adsorption-catalytic oxidation experiments indicates that adsorption plays an important role in the catalytic oxidation of phenol by decreasing the phenol degradation time. Spin density and adsorption modeling demonstrates that graphitic N in N-rGO plays the most important role for the catalytic performance by inducing high positive charge densities to adjacent carbon atoms and facilitating phenol adsorption on these carbon sites. Furthermore, the activation mechanism of persulfate (PS) on N-rGO was first investigated by DFT method and PS can be activated to generate strongly oxidative radical (SO4·-) by transferring electrons to N-rGO.

Study on the catalysts of sulfur-odor gas pollution treatment

Aiming at the characteristics and current status of refineries’ odor pollution, the sulfur containing odor gas–hydrogen sulfide was chosen as a typical object and treated by using the adsorption-catalytic oxidation method in the laboratory. This research focused on the preparation of adsorptive catalyst with high sulfur capacity at room temperature. The results showed that the sulfur capacity of walnut shell activated carbon (WSAC) was up to 351 mg/g, specific surface area was 2,030 m2/g, and the pore volume of microspores was 0.608 mL/g. By comparison with the commercial activated carbon, it is found that the specific surface area, the sulfur capacity, and iodine value of WSAC have been improved significantly. The sulfur capacity of WSAC modified by KIO3 with mass fraction of 1 % was up to 459 mg/g.

Removal of Terephthalic Acid from Waste Water Using Diatomite Adsorbent

Adsorption-catalytic oxidation of terephthalic acid (TA) from waster water using modified diatomite adsorbent was studied in this paper. Two diatomites were chosen for adsorbents and TA was used as a model compound. The process consists of physic adsorption of TA and catalytic oxidation of TA. The concentration of TA was determined by UV spectrometry. The results indicate that adsorption capacity of diatomite increased with the decrease of pH value of waster water. The equilibrium adsorbed amount of modified diatomite increased with the increase of metal content in the initial metal content range from 0 to 5% for both of Ni, Fe and Cu modified diatomite, and then the equilibrium adsorbed amount decreased after 5% metal content for Ni modified diatomite and in general kept constant for Fe and Cu modified diatomite. The maximum amount of TA adsorbed at the equilibrium stage was 4.40mg/g for Ni-5/RD. The adsorption capacity of raw and modified diatomite decreased obviously with the increase of cycle number in the initial first-fourth of cycle and then decreased very slowly in the 5th-10th of cycle. The Qe of Ni-5/RD, Fe-5/RD, Cu-5/RD and RD in the 10th cycle were 3.12, 2.44, 1.87 and 0.12mg/g, respectively. The result indicated that the modified could be repeatedly used and maintained the adsorption/regeneration performance stably through many batches of operation.

Optimization of air-borne butyl acetate adsorption on dual-function Ag–Y adsorbent-catalyst using response surface methodology

The low concentration and high flow rate of air-borne butyl acetate (BA) could be effectively removed using combined adsorption-catalytic oxidation system. Ag–Y (Si/Al = 80) dual-function adsorbent was investigated for the adsorption step of 1000 ppm of butyl acetate at gas hourly space velocity of 13,000 h −1 at ambient temperature under dry and humid feeds. A central composite design (CCD) coupled with response surface methodology (RSM) was employed to obtain the optimum process conditions and the interactions between process variables were demonstrated and elucidated. Humidity and increasing organic concentration shortened the adsorption service time. The effect of moisture was more pronounced at low BA concentration. The interactions between the BA concentration and humidity were statistically significant at 95% confidence level. The optimum conditions were found to be at 4500 ppm of BA with 37 min saturation time to give 58 mg BA/g as adsorption capacity. The simulated data fitted the experimental data satisfactorily. The simulated data also correctly demonstrated the overall behaviors of the adsorption process.