Comparative study of the adsorption performance of NH_(2)-functionalized metal organic frameworks with activated carbon composites for the treatment of phenolic wastewaters

To better understand the role of the-NH_(2)group in adsorption process of phenolic wastewaters,NH_(2)-functionalized MIL-53(Al)composites with activated carbon(NH_(2)-M(Al)@(B)AC)were prepared.The results showed that the-NH_(2)group could increase the mesopore volume for composites,which promotes mass transfer and full utilization of active sites,because hierarchical mesopore structure makes the adsorbent easier to enter the internal adsorption sites.Furthermore,the introduction of the-NH_(2)group can improve the adsorption capacity,decrease the activation energy,and enhance the interaction between the adsorbent and p-nitrophenol,demonstrating that the-NH_(2)group plays a crucial role in the adsorption of p-nitrophenol.The density functional theory calculation results show that the H-bond interaction between the-NH_(2)group in the adsorbent and the-NO_(2)in the p-nitrophenol(adsorption energy of -35.5 kJ·mol^(-1)),and base-acid interaction between the primary-NH_(2)group in the adsorbent and the acidic-OH group in the p-nitrophenol(adsorption energy of -27.3 kJ·mol^(-1))are predominant mechanisms for adsorption in terms of the NH_(2)-functionalized adsorbent.Both NH_(2)-functionalized M(Al)@AC and M(Al)@BAC composites exhibited higher p-nitrophenol adsorption capacity than corresponding nonfunctionalized composites.Among the composites,the NH_(2)-M(Al)@BAC had the highest p-nitrophenol adsorption capacity of 474 mg·g^(-1).

Treatment of Phenol Wastewater with Cu-Fe/AC Catalyst by Continuous CWPO

The Cu-Fe/AC catalyst was prepared by microwave-assisted synthesis, and its morphological characteristics were characterized. The degradation effect of phenol wastewater by catalytic wet peroxide oxidation(CWPO) was studied, and the response surface methodology(RSM) was used to analyze the influencing factors of the removal rate of COD. The experimental results showed that under the conditions of reaction temperature 80 ℃, reaction time 90 min, initial pH 3.1 and H_(2)O_(2)addition 2.2 g/L, the removal rate of COD reached 82%. The results of response surface methodology indicated that under the conditions of reaction temperature 100 ℃, reaction time 64 min, initial pH 3.3 and H_(2)O_(2)addition 2.7 g/L, the removal rate of COD was up to 86%. After Cu-Fe/AC catalyst was reused for 4 times, the removal rate of COD was still above 80%, revealing that the catalyst showed good catalytic performance.

Treatment of phenol wastewater by microwave-induced CIO_2-CuO_x/Al_2O_3 catalytic oxidation process

The catalyst of CUOx/Al2O3 was prepared by the dipping-sedimentation method using y-Al2O3 as a supporter. CuO and Cu2O were loaded on the surface of Al2O3, characterized by X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. In the presence of CuOx/Al2O3, the microwave-induced chlorine dioxide （ClO2） catalytic oxidation process was conducted for the treatment of synthetic wastewater containing 100 mg/L phenol. The factors influencing phenol removal were investigated and the results showed that microwave-induced C102-CuOx/ml203 process could effectively degrade contaminants in a short reaction time with a low oxidant dosage, extensive pH range. Under a given condition （ClO2 concentration 80 mg/L, microwave power 50 W, contact time 5 latin, catalyst dosage 50 g/L, pH 9）, phenol removal percentage approached 92.24%, corresponding to 79.13% of CODcr removal. The removal of phenol by microwave-induced ClO2-CuOx/Al2O3 catalytic oxidation process was a complicated non-homogeneous solid/water reaction, which fitted pseudo-first-order by kinetics. Compared with traditional ClO2 oxidation, ClO2 catalytic oxidation and microwave-induced ClO2 oxidation, microwave-induced ClO2 catalytic oxidation system could significantly enhance the degradation efficiency. It provides an effective technology for the removal of phenol wastewater.

Several Rules for Treating Phenol Wastewater via Oxidation by O_3/UV-formed Radicals

The treatment of phenol wastewater with an ultraviolet source and an oxone generator by introducing salicylic acid as the capturer is described. The presence of HO during the phenol degradation has been proved. The impacts of factors such as acidity and reaction time on the HO formation are also discussed. The results demonstrate that HO ＇ generated from ozone/UV oxidation under a basic condition is the immediate cause of phenol degradation. At room temperature and a pH value of 9. 93, the degradation of phenol occurs rapidly within 0. 5 rain and the removal of phe- nol（ 100 mg/L） is above 98. 5% within 15 min; in the meantime, the pH value declines gradually with the degradation of phenol. A discussion about the formation and the transformation of the intermediate products during phenol degradation is included.

Comparative study on the degradation of phenol by a high-voltage pulsed discharge above a liquid surface and under a liquid surface

The degradation of phenol by pulsed discharge plasma above a liquid surface(APDP) and under a liquid surface(UPDP) was compared.The effects of discharge voltage,discharge distance,initial solution conductivity and initial p H on the removal of phenol were studied.It was concluded that the removal of phenol increases with increasing discharge voltage and with decreasing discharge distance in both APDP and UPDP systems.An increase in the initial solution’s conductivity has a positive effect in the APDP system but a negative effect in the UPDP system.In addition,alkaline conditions are conducive to the degradation of phenol in the APDP system,while acidic conditions are conducive in the UPDP system.Free radical quenching experiments revealed that ·O-2has an important influence on the degradation of phenol in the APDP system,while ·OH plays a key role in the UPDP system.This paper verifies the differences in the two discharge methods in terms of phenol removal.

Phenol contaminated municipal wastewater treatment using date palm frond biochar:Optimization using response surface methodology

Phenol is classified as an emerging contaminant which can be very toxic even at low concentrations and should be removed from wastewaters before reaching the environment.In this study date palm frond and leaf were pyrolyzed at different temperatures to identify the best adsorbent(feedstock)and pyrolysis temperature to remove phenol from aqueous solutions.Date palm frond pyrolyzed at 600℃,termed DPF600,achieved the highest phenol removal rates of 64%and adsorption capacity of 15.93 mg/g.Response surface methodology approach using Box-Behnken design was implemented to obtain the optimal pH(6),contact time(20 h)and dosage(0.1 g)for the maximum phenol adsorption.A predicted adsorption capacity was found as 16.62 mg/g which was in close agreement with the experimental adsorption capacity of 17.38 mg/g.Isotherm and kinetic models in both linear and non-linear forms indicated that Freundlich model(R^(2)=0.99,χ^(2)=0.02,RMSE=1.09)and pseudo-second order model(R^(2)=0.99,χ^(2)=0.85,RMSE=5.41)fit best the obtained experimental data.Thermodynamics calculations affirmed that the adsorption of phenol onto DPF600 biochar was endothermic and spontaneous.The point of zero charge was found to be at 6.5 for DPF600 biochar.Scanning electron microscopy coupled with energy dispersive X-ray,Fourier transform infrared spectroscopy and X-ray diffraction confirmed adsorption of phenol onto DPF600 biochar.Application of DPF600 biochar to remove phenol from synthetic primary and secondary treated wastewater samples achieved 60 and 85%removal rates and 241 mg/g and 22.28 mg/g adsorption capacities,respectively.Regeneration studies showed promising adsorption capacities indicating the efficacy of DPF600 for the removal of phenol from wastewater.

Design of solvent mixtures for removal of phenol from wastewater using a non-linear programming model with a multi-start method

The optimization-based design of solvent mixtures used for phenolic wastewater treatment was investigated in this work.A nonlinear programming(NLP)model was formulated based on the concepts of computer-aid molecule design(Computer-Aided Molecular Design,CAMD)to select solvent mixtures with the best extraction performance considering the constraints of extraction process and the environmental impact.Due to the complexity of the NLP model,multi-start method was adopted to solve this problem in order to get near global optimal solution.The results of the calculations suggested that the optimal mixture consisted of 70.1%n-octanol and 29.9%2-octanone(molar fraction).The 119 sets of experimental results showed that the extraction ability of the optimal solvent mixture identified by CAMD technique was among the top 6 sets compared to the experiment results.The results suggested that the developed NLP model could be able to screen the optimal solvent mixture in phenolic wastewater treatment.

Influence of phenol on ammonia removal in an intermittent aeration bioreactor treating biologically pretreated coal gasification wastewater

A laboratory-scale intermittent aeration bioreactor was investigated to treat biologically pretreated coal gasification wastewater that was mainly composed of NH_3-N and phenol.The results showed that increasing phenol loading had an adverse effect on NH_3-N removal;the concentration in effluent at phenol loading of 40 mg phenol/（L·day） was 7.3 mg/L, 36.3%of that at 200 mg phenol/（L·day）. The enzyme ammonia monooxygenase showed more sensitivity than hydroxylamine oxidoreductase to the inhibitory effect of phenol, with32.2% and 10.5% activity inhibition, respectively at 200 mg phenol/（L·day）. Owing to intermittent aeration conditions, nitritation-type nitrification and simultaneous nitrification and denitrification（SND） were observed, giving a maximum SND efficiency of 30.5%.Additionally, ammonia oxidizing bacteria（AOB） and denitrifying bacteria were the main group identified by fluorescent in situ hybridization. However, their relative abundance represented opposite variations as phenol loading increased, ranging from 30.1% to 17.5%and 7.6% to 18.2% for AOB and denitrifying bacteria, respectively.