Performances and mechanisms of efficient degradation of atrazine using peroxymonosulfate and ferrate as oxidants

Effect of salinity on removal performance and activated sludge characteristics in sequencing batch reactors.

The profound growth and development of industrial segments discharge enormous quantities of phenolic pollutants into the aquatic environment. Phenolic compounds are priority pollutants and their presence in the water system causes severe hazards to human health and many other living creatures. Thus, the removal of such toxic pollutants has gained a lot of attention in the past few decades. Biodegradation is a sustainable and efficient method for the removal of phenolic pollutants from the aquatic environment. Though microbial degradation of phenolic pollutants is well documented, enzymatic metabolic pathways, co-metabolic biodegradation, the use of sequential bioreactors, and the treatment of real-world industrial wastewater have yet to be adequately addressed. Therefore, the present review focuses on the assessment of biological removal of phenolic pollutants from the contaminated environment along with the various associated problems. In particular, the mechanism of ecotoxicity of phenolic pollutants on the living system, the functional enzymes and metabolic pathways involved in microbial degradation, including co-metabolic and co-culture degradation of phenolic pollutants, were elaborately reviewed. The use of aerobic granular sludge (AGS) in the treatment of recalcitrant wastewater has been addressed. The performances of various bioreactor systems are also compared. The prospects for resource recovery by photosynthetic bacteria that degrade phenolics are also discussed. 

A comprehensive review on eco-toxicity and biodegradation of phenolics: Recent progress and future outlook

The rapid increase in saline wastewater discharge has severely affected the aquatic environment. Furthermore, the presence of salinity in the wastewater severely limits the performance of many wastewater treatment techniques. In this context, the present review article has reported the sources of saline wastewater and its environmental impacts. Wastewater originating from agricultural fields, and various industries, such as aquaculture, tannery, petrochemical, pharmaceuticals, etc., contain a high degree of salinity. The performance of different physicochemical, biological, and hybrid systems in terms of treatment of saline wastewater has been investigated. High salinity levels were found to negatively impact the performance of various physicochemical processes (9 ± 41%) and biological treatment techniques (25 ± 31%). However, processes such as electrochemical oxidation and biological processes operating in the presence of salt-tolerant bacteria showed excellent performance in high salinity. High salinity showed minimal impact on the performance of hybrid systems, which were designed for treating saline wastewater. In this review, the effects of increased salinity on the controlling parameters of various processes have also been elucidated. Recommendations, such as the incorporation of additional pre-treatment units, augmentation of biological systems by salt-tolerant bacteria such as halophiles, etc., have been proposed, which may help to curb down the detrimental effects of high salinity. The present study circumscribes the different aspects of the treatment of saline wastewater, which may be helpful for environmental engineers and researchers working in this field.

Treatment of saline wastewater using physicochemical, biological, and hybrid processes: Insights into inhibition mechanisms, treatment efficiencies and performance enhancement

Aquatic contamination of diclofenac (DCF), an emergent non-steroidal anti-inflammatory drug (NSAIDs), can result in adverse effects to many ecosystems through biomagnification. Hence, introducing effective remediation techniques to sequester the pharmaceutical wastes is highly fundamental to prevent their accumulation in the environment. Generally, adsorption has been presented as a green and efficient approach. Herein, we report the characterization and application of the novel magnetic nanocomposite (GO@CoFe2O4) derived from cobalt-based ferrite (CoFe2O4) and graphene oxide (GO) for DCF adsorption. For the optimization procedure, the response surface methodology (RSM) was adopted to investigate the impacts of DCF concentration (1.6–18.4 mg/L), DCF dosage (0.08–0.92 g/L), and solution pH (2.6–9.4) to find the optimum conditions for DCF removal, at 10.5 mg/L, 0.74 g/L, and pH 4, respectively. For the adsorption experiments, the kinetic, isotherm, thermodynamic, and intraparticle diffusion models were systematically studied. Moreover, we have elucidated the role of functional groups on the surface of GO@CoFe2O4 in enhancing the adsorption of DCF drug. With good removal efficiency (up to 86.1%), high maximum adsorption capacity (32.4 mg/g), GO@CoFe2O4 can be a potential candidate to eliminate DCF drug from water.

Optimization, equilibrium, adsorption behavior and role of surface functional groups on graphene oxide-based nanocomposite towards diclofenac drug.

In this study, the performance of 3,5-dimethyl-2,4-dichlorophenol (DCMX) degradation by a screened strain was investigated. 18S rDNA and the neighbor-joining method were used for identification of the isolated strain. The results of phylogenetic analysis and scanning electron micrographs showed that the most probable identity of the screened strain should be Penicillium sp. Growth characteristics of Penicillium sp. and degradation processes of DCMX were examined. Fourier transform infrared spectroscopy of the inoculated DCMX solution was recorded, which supported the capacity of DCMX degradation by the screened Penicillium sp. Under different salinity conditions, the highest growth rate and removal efficiency for DCMX were obtained at pH6.0. The removal efficiency decreased from 100% to 66% when the DCMX concentration increased from 5 to 60mg/L, respectively. Using a Box-Behnken design, the maximum DCMX removal efficiency was determined to be 98.4%. With acclimation to salinity, higher removal efficiency could be achieved. The results demonstrate that the screened Penicillium sp. has the capability for degradation of DCMX.

Biodegradation of 3,5-dimethyl-2,4-dichlorophenol in saline wastewater by newly isolated Penicillium sp. yz11-22N2.

Naphthalene-2-ol is a typical biologically recalcitrant pollutant in dye wastewater. Solvent extraction of naphthalene-2-ol from aqueous solutions using mixed solvents was investigated. Various extractants and diluents were evaluated, and the effects of volume ratio of extractant to diluent, initial pH, initial concentration of naphthalene-2-ol in aqueous solution, extraction time, temperature, volume ratio of organic phase to aqueous phase (O/A), stirring rate and extraction stages, on extraction efficiency were examined separately. Regeneration and reuse of the spent extractant were also investigated. Results showed that tributyl phosphate (TBP) achieved 98% extraction efficiency for naphthalene-2-ol in a single stage extraction, the highest among the 12 extractants evaluated. Extraction efficiency was optimized when cyclohexane and n-octane were used as diluents. The solvent combination of 20% TBP, 20% n-octanol and 60% cyclohexane (V/V) obtained the maximum extraction efficiency for naphthalene-2-ol, 99.3%, within 20min using three cross-current extraction stages under the following extraction conditions: O/A ratio of 1:1, initial pH of 3, 25°C and stirring rate of 150r/min. Recovery of mixed solvents was achieved by using 15% (W/W) NaOH solution at an O:A ratio of 1:1 and a contact time of 15min. The mixed solvents achieved an extraction capacity for naphthalene-2-ol stably higher than 90% during five cycles after regeneration.

Efficient removal of naphthalene-2-ol from aqueous solutions by solvent extraction

The recovery of gallic acid (GA) from GA processing wastewater was studied via solvent extraction. Tributyl phosphate (TBP)/4-methyl-2-pentanone (MIBK)/n-hexane, TBP/n-octanol/n-hexane and n-hexanol were used as the extractants. The effects of the component proportion in the mixed extraction solvent, stirring speed, extraction time, pH, phase ratio (extraction solvent/GA solution), temperature and salt on extraction rate were investigated. After univariate crossover experiments, the optimum conditions were obtained as a component proportion in the mixed extraction solvent of 1:2:1 at pH 1.5 with a phase ratio of 1:1, stirring speed of 150 rpm, extraction time of 60 s and temperature of 30 °C. The maximum extraction rates through the one-stage process were 88.2%, 82.5% and 76.7% for TBP/MIBK/n-hexane, TBP/n-octanol/n-hexane and n-hexanol, respectively. FT-IR spectroscopy was used to characterize the extracted organic phases. Afterwards, Box–Behnken design was used to optimize the three most influential parameters including pH, temperature and phase ratio whose values were optimized to 0.5, 30 °C and 1:1, respectively and subsequently, the extraction rate through the one-stage process using TBP/MIBK/n-hexane, TBP/n-octanol/n-hexane and n-hexanol further increased to 95.5%, 86.8% and 78.1%, respectively. TBP/MIBK/n-hexane was proved to be the most effective extractant in this study and more than 94.4% of GA was recovered through a four-stage stripping process. Finally, TBP/MIBK/n-hexane was used in actual GA processing wastewater with 92.5% of GA being extracted and more than 88.7% was recovered after the four-stage extraction and stripping process. The results can be referred to for the selection and design of processes to efficiently recover GA from GA processing wastewater.

The recovery of gallic acid from wastewater by extraction with tributyl phosphate/4-methyl-2-pentanone/n-hexane, tributyl phosphate/n-octanol/n-hexane and n-hexanol

The invention relates to a preparation method of a catalyst for catalytic oxidation desulfurization. The method comprises the following steps: grinding medical stone (MFS) original sample into 60-120 meshes, repeatedly washing with deionized water, drying for 4-6 hours at the vacuum of 120 DEG C, then carrying out high-temperature calcination for 1-3 hours in a muffle furnace of 400 DEG C, washing and drying after cooling, soaking the medical stone in 1-2mol/L hydrochloric acid, filtering, drying, soaking modified medical stone in an 15-20% ammonium molybdate solution, stirring for 3-5 hours, and then standing for 6-8 hours, wherein the temperature is kept at 30 DEG C all the time; filtering, drying at the vacuum of 50-80 DEG C until reaching constant weight, finally carrying out high-temperature calcination for 1-2 hours in the muffle furnace of 400 DEG C, and cooling, thus preparing the catalyst Mo/MFS which is good in effect and can be applied to catalytic oxidation desulfurization reaction. The method has the advantages of simplicity, low cost and easily available materials, and the prepared catalyst is good in desulfurization effect and high in repeated utilization factor.

Preparation method of catalyst for catalytic oxidation desulfurization

The invention discloses a method for treating 2, 4-dichloro-3, 5-dimethylphenol (DCMX) waste water. The method comprises the following steps: (1) extracting DCMX: acidifying DCMX waste water, then adding a complexing extraction agent tributyl phosphate-kerosene, uniformly stirring, carrying out the extraction, extracting the DCMX into an organic phase, after the extraction is ended, standing, carrying out the layering to obtain the organic phase containing the DCMX; (2) re-extracting and recovering DCMX: adding sodium hydroxide into the organic phase containing the DCMX, converting the DCMX to sodium salt of the DCMX, transferring the sodium salt of the DCMX into a water phase from the organic phase, and recovering the pure sodium salt solution of DCMX. By adopting the method, more than 82 percent of DCMX in the waste liquid can be recovered, the waste of resources in avoided, an extraction agent can be recycled, and fewer agents are consumed. The method has advantages of high treatment efficiency, simplicity in operation, moderate conditions, easiness in control and the like; moreover, the extraction agent can be reused, so that the cost is reduced, and the sodium salt of the DCMX in the waste water also can be used as a resource to be recycled.

Extraction treatment method for 2, 4-dichloro-3, 5-dimethylphenol waste water

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