RESUMO
A new N-doped biochar derived from sugarcane bagasse (NSB) was prepared by one-pot pyrolysis with sugarcane bagasse as feedstock, melamine as nitrogen source and NaHCO3 as pore-forming agent, and then NSB was used to adsorb ciprofloxacin (CIP) in water. The optimal preparation conditions of NSB were determined based on the evaluation index of adsorbability of NSB for CIP. SEM, EDS, XRD, FTIR, XPS and BET characterizations were used to analyze the physicochemical properties of the synthetic NSB. It was found that the prepared NSB had excellent pore structure, high specific surface area and more nitrogenous functional groups. Meanwhile, it was demonstrated that the synergistic interaction between melamine and NaHCO3 increased the pores of NSB and the largest surface area of NSB was 1712.19 m2/g. The CIP adsorption capacity of 212 mg/g was obtained under optimal parameters as follows: NSB amount 0.125 g/L, initial pH 6.58, adsorption temperature 30 °C, CIP initial concentration 30 mg/L and adsorption time 1 h. The isotherm and kinetics studies elucidated that the adsorption of CIP conformed both D-R model and Pseudo-second-order kinetic model. The high CIP adsorption capacity of NSB for CIP was due to the combined filling pore, π-π conjugation and hydrogen bonding. All results demonstrated that adsorption of CIP by the low-cost N-doped biochar of NSB is a reliable technology for the disposal of CIP wastewater.
Assuntos
Saccharum , Poluentes Químicos da Água , Ciprofloxacina/química , Celulose , Adsorção , Porosidade , Poluentes Químicos da Água/química , Carvão Vegetal/química , CinéticaRESUMO
Red mud (RM), a kind of iron-rich industrial waste produced in the alumina production process, can be utilized as a potential iron-based material for the removal of refractory organic pollutants from wastewater in advanced oxidation processes (AOPs). In this work, high-iron RM (rich in iron) was activated in a ball mill and applied as an effective activator of peroxymonosulfate (PMS) for tetracycline hydrochloride (TC-HCl) degradation. Compared with that of unmilled RM (69.7%), the TC-HCl decomposition ratios of ball-milled RM (BM-RM) (72.2%-92.0%) were all improved in the presence of PMS. Systematic characterization suggested that ball milling could optimize the physicochemical properties of RM, such as increased surface area, increased oxygen vacancies, enhanced electrical conductivity, and increased exposure of Fe(II) sites, all of which could effectively improve RM for PMS activation to degrade TC-HCl. The quenching experiments and electron paramagnetic resonance technique revealed that 1O2 and SO4·- contributed dominantly to the TC-HCl degradation. Ultra performance liquid chromatography mass spectrometry analysis combined with density functional theory calculation revealed that the degradation pathways of TC-HCl were driven by hydroxylation, N-demethylation and dehydration in BM-RM/PMS system. Based on quantitative structure-activity relationship prediction using the Toxicity Estimation Software Tool software, the toxicity of almost all intermediates was significantly reduced. An obvious inhibition effect on TC-HCl was occurred in the presence of Cl-, whereas the presences of NO3- and SO42- had little effect. However, HCO3- improved TC-HCl removal efficiency. BM-RM had a wide working pH range (pH = 3-11) and showed good stability and reusability in use. Overall, this work not only offers a simple and promising approach to improve the catalytic activity of RM, but also opens new insights into the ball-milled RM as an effective PMS activator for wastewater treatment.
Assuntos
Peróxidos , Tetraciclina , Peróxidos/química , Catálise , Ferro/químicaRESUMO
In this study, using bentonite-supported Fe(II)/phosphotungstic acid composite (HPW-Fe-Organicbent) prepared by mechanochemical synthesis as heterogeneous catalyst, the photo-Fenton degradation of ethyl xanthate under visible light irradiation was studied in detail. The results showed that the degradation of ethyl xanthate was mainly impacted by H2O2 dosage, catalyst dosage and reaction time. HPW-Fe-Organicbent catalyst had a wide applicable range of pH and kept a high catalytic activity even at high pH in the photo-Fenton degradation of ethyl xanthate. It was found that the degradation of ethyl xanthate in the photo-Fenton process catalyzed by HPW-Fe-Organicbent mainly resulted from the hydroxyl radicals. HPW-Fe-Organicbent had an excellent stability in use, and retained almost all of its catalytic activity for four recycling times. Moreover, the kinetics study showed the degradation of ethyl xanthate, with the initial concentration below 50 mg/L, was well fitted by the pseudo-first-order rate model.
Assuntos
Bentonita/análise , Compostos Ferrosos/análise , Peróxido de Hidrogênio/química , Ácido Fosfotúngstico/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Cinética , Luz , FotóliseRESUMO
Antibiotic was detected in many environments, and it had posed a serious threat to human health. The advanced oxidation process has been considered an effective way to treat antibiotics. In this work, using industrial waste red mud (RM) as raw material, a series of modified RM (MRM-T; T donates the calcination temperature) was obtained via a facile calcination method and applied to activate sodium bisulfite (NaHSO3) for the lomefloxacin (LOM) degradation. Among all MRM-T, MRM-700 exhibited superior catalytic activity, and approximately 89% of LOM (10 mg/L) was degraded at 30 min through the activation of NaHSO3 ([NaHSO3] = 0.5 g/L) by MRM-700 ([MRM-700] = 0.9 g/L). Moreover, the kinetic constant of LOM removal in the MRM-700/NaHSO3 system (0.082 min-1) was 16.4 times higher than that of the RM-raw/NaHSO3 system (0.005 min-1). The as-synthesized product of MRM-700 was characterized by N2 adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectra. The result indicated that the catalyst possessed excellent pore structure, high specific area, and abundant Fe3+ sites, and the lattice of Fe2O3 was doped after calcination, both of which were favorable for the activation of NaHSO3. The quenching experiment proved that â¢SO4- and â¢OH- active species were produced in MRM-700/NaHSO3 system, and â¢SO4- played a dominant role in LOM removal. In addition, the potential LOM degradation pathway was analyzed via UPLC-MS technology and density functional theory (DFT) calculation, and the toxicity of the treated LOM solution was tested by the culture of mung bean sprouts. This study not only provided a feasible strategy for the valuable use of RM to activate NaHSO3 but also offered a cost-effective catalyst for the efficient removal of pollutants in wastewater.
Assuntos
Espectrometria de Massas em Tandem , Humanos , Cromatografia Líquida , CatáliseRESUMO
A catalyst consisting of phosphotungstic acid (H3PW12O40) combined with activated clay was prepared by the impregnation method, and an experiment was carried out to evaluate the catalytic activity of the H3PW12O40/activated clay for the degradation of methyl orange (MO) in the UV-H2O2 process. The degradation ratio of MO can be affected by H2O2 concentration, reaction time, catalyst dosage, pH and temperature. The reaction temperature should be controlled at less than 70 degrees C, and the catalyst has a wide applicable pH range in the UV-H2O2 process. Hydroxyl radicals were generated in the UV-H2O2 system under the action of H3PW12O40/activated clay, and MO was degraded by hydroxyl radicals. Compared with traditional catalysts used in UV-H2O2 systems, H3PW12O40/activated clay has certain advantages for its practical application.
Assuntos
Compostos Azo/química , Peróxido de Hidrogênio/química , Poluentes Químicos da Água/química , Silicatos de Alumínio , Catálise , Argila , Corantes/química , Concentração de Íons de Hidrogênio , Radical Hidroxila , Ácido Fosfotúngstico , Reciclagem , Temperatura , Fatores de Tempo , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Difração de Raios XRESUMO
In this work, using molasses wastewater as a partial acidifying agent and bagasse pith as a pore-enlarging agent, a new low-cost Fenton-like catalyst (ACRMbp) used for degradation of sulfamethoxazole was prepared through a simple process of acidification and calcination using red mud (RM) as the main material. The optimum preparation conditions of ACRMbp were acquired, and the optimum preparation conditions of ACRMbp were as follows: mass ratio of bagasse pith to RM (mbp:mRM) 0.033:1, particle size of bagasse pith 0.10-0.20â mm, calcination temperature 773â K, and calcination time 2â h. The ACRMbp catalyst was characterized by XRD, SEM, EDS, and BET. According to the results of characterizations, it was found that the iron phase of ACRMbp had completely transformed into α-Fe2O3 after the process of acidification and calcination, and the addition of bagasse pith significantly improved the surface area of the prepared ACRMbp. Furthermore, under the reaction conditions of catalyst dosage of 2â g/L, initial pH 3 and reaction time 90â min, the ACRMbp has showed the highest catalytic activity. ACRMbp had significantly higher activity than red mud, and exhibited a remarkable settleability. Besides, ACRMbp retained good recyclability and stability during use. Kinetic studies showed the degradation process could be described with the first-order model. Overall, the prepared ACRMbp was an effective and excellent catalyst in the Fenton-like process.
Assuntos
Peróxido de Hidrogênio , Sulfametoxazol , Catálise , Peróxido de Hidrogênio/química , Ferro/química , CinéticaRESUMO
In this work, using an agricultural waste of sugarcane bagasse, new biomass of magnetic sugarcane bagasse activated carbon (MSBAC) has been successfully prepared by a simple microwave method. The composition and structure of MSBAC were characterised by SEM, XRD, BET, and FT-IR. It was found that MSBAC was a mesoporous material with a loose structure and rough surface, and it had a high specific surface area. The pHPZC was 4.1, and MSBAC presented a greater amount of acid functional groups than basic groups, making it efficient for adsorption of cationic dye. To study the adsorption ability of MSBAC, methylene blue (MB) was selected as sample pollutant. Effects of pH, MSBAC dosage, initial MB concentration, temperature, time on the adsorption of MB, and the possibility of regeneration of MSBAC were investigated. The adsorption results showed that the maximum adsorption capacity was 36.14â mg·g-1, and the pH had no significant effect on the MB adsorption in the range of 2-10. The equilibrium data fitted Langmuir isotherm, and the adsorption kinetic data obeyed pseudo-second-order kinetic model. The adsorption process involving the surface diffusion and film diffusion. The positive value of ΔH revealed the adsorption behaviour was an endothermic process. The salt concentration had a negative effect on MB removal. MSBAC had a good magnetic separation performance. The used MSBAC could be regenerated by a simple calcination method under the temperature of 300â for 30â min.
Assuntos
Saccharum , Poluentes Químicos da Água , Adsorção , Celulose , Carvão Vegetal , Compostos Férricos , Concentração de Íons de Hidrogênio , Cinética , Azul de Metileno , Micro-Ondas , Espectroscopia de Infravermelho com Transformada de Fourier , ÁguaRESUMO
In this work, using industrial waste red mud (RM) as main starting material, a simple method of mechanochemical synthesis (MCS) was introduced as a green approach to synthesize heterogeneous Fe2O3/Zn-Al layered double hydroxide (F/ZA-LDH), which could be used as a new low-cost catalyst for photo-Fenton reaction. The optimum preparation conditions of F/ZA-LDH were as follows: mass ratio of Zn(NO3)2·6H2O to RM (mZn:mRM) 2:1, dry milling time 6 h, H2O dosage 2 mL, ball-to-powder mass ratio 50:1, and milling speed 250 rpm. The effects of the synthesis conditions on the crystal structure and catalytic activity of F/ZA-LDH were analyzed. The F/ZA-LDH was characterized by XRD, TG, XPS, SEM, (HR)TEM. The characterization results showed the composite had a crystallized hydrotalcite-like structure, and the crystalline phases in the optimum F/ZA-LDH were Fe2O3 and Zn-Al LDH. A hetero-interfaces between Fe2O3 and Zn-Al LDH existed in the synthesized Fe2O3/Zn-Al LDH composite. Furthermore, the possible mechanism for F/ZA-LDH formation in the MCS process was proposed. Overall, our results provide a systematic understanding of the preparation of LDH composite through MCS using RM as main material, and our findings help to develop green technology for reusing RM.
RESUMO
To obtain information about dechlorination of organochlorine compounds in subcritical water catalyzed by metals assisted with ZrO(2), dechlorination of chlorobenzene has been investigated in the presence of Fe/ZrO(2), Ni/ZrO(2) and Cu/ZrO(2) catalysts. The dechlorination efficiency was increased with increasing residence time, temperature and pressure. The order of effectiveness of the catalysts was Cu/ZrO(2) < Ni/ZrO(2) < Fe/ZrO(2). The dechlorination of chlorobenze obeyed pseudo-first-order kinetics models. The rate constants in subcritical water were much greater than that in ambient-temperature water; the activation energies were obtained. ZrO(2) in the catalyst had the power to absorb chlorobenzene onto the catalyst surface and promoted the dechlorination ability of the metal. The primary mechanism for dechlorinaton of chlorobenzene involved the reduction of chlorobenzene by reaction with nascent hydrogen. The nascent hydrogen reacted with the chlorobenzene, which adsorbed on the catalyst in non-planar and co-planar form, and formed benzene and chloride ions.
Assuntos
Clorobenzenos/química , Cobre/química , Ferro/química , Níquel/química , Zircônio/química , Catálise , Poluentes Químicos da Água/químicaRESUMO
Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRM sm ) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H2SO4 and molasses wastewater, and the prepared ACRM sm was a near-neutral catalyst. The ACRM sm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H2SO4 plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRM sm was mainly α-Fe2O3 and trace amount of carbon existed in ACRM sm . The addition of molasses wastewater not only effectively reduced the consumption of H2SO4 in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRM sm . It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRM sm . The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRM sm retained most of its catalytic stability and activity after five recycling times, indicating ACRM sm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRM sm had an excellent settleability. ACRMsm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.
Assuntos
Melaço , Águas Residuárias , Catálise , Compostos Férricos , FerroRESUMO
Acidified/calcined red mud (ACRM), a novel catalyst used in Fenton-like process, was prepared by acidification and calcination of red mud (RM). Catalyst characterization showed that iron phase of ACRM was mainly α-Fe2O3 and ACRM was a porous material with rough surface and loose structure. Degradation of butyl xanthate in Fenton-like process catalyzed by ACRM was investigated. Butyl xanthate was effectively degraded, and the degradation of butyl xanthate was well fitted by second order kinetic model. ACRM had an excellent long-term stability in a Fenton-like process. The possible mechanisms of hydroxyl radical production and butyl xanthate degradation in a Fenton-like process catalyzed by ACRM were presented.