Biodegradation of naphthalene by biocatalysts isolated from the contaminated environment under optimal conditions.

Polycyclic aromatic hydrocarbons (PAHs) pollution occurs in freshwater and marine environment by anthropogenic activities. Moreover, analysis of the PAHs-degradation by the indigenous bacterial strains is limited, compared with other degraders. In this study, naphthalene (NAP) biodegrading bacteria were screened by enrichment culture method. Three bacterial strains were obtained for NAP degradation and identified as Bacillus cereus CK1, Pseudomonas aeruginosa KD4 and Enterobacter aerogenes SR6. The amount of hydrogen, carbon, sulphur and nitrogen of wastewater were analyzed. Total bacterial count increased at increasing incubation time (6-60 days) and moderately decreased at higher NAP concentrations. The bacterial population increased after 48 days at 250 ppm NAP (519 ± 15.3 MPM/mL) concentration and this level increased at 500 ppm NAP concentration (541 ± 12.5 MPM/mL). NAP was degraded by bacterial consortium within 36 h-99% at 30 °C. PAHs degrading bacteria were grown optimally at 4% inoculum concentrations. Bacterial consortium was able to degrade 98% NAP at pH 7.0 after 36 h incubation and degradation potential was improved (100%) after 34 h (pH 8.0). Also at pH 9.0, 100% biodegradation was registered after 36 h incubation. When the agitation speed enhanced from 50 ppm to 150 ppm, increased bacteria growth and increased NAP degradation within 42 h incubation. Among the nutrient sources, beef extract, peptone and glucose supplemented medium supported complete degradation of PAHs within 30 h, whereas peptone supported 94.3% degradation at this time. Glucose supplemented medium showed only 2.8% NAP degradation after 6 h incubation and reached maximum (100%) within 42 h incubation. Bacterial consortium can be used to reduce NAP under optimal process conditions and this method can be used for the removal of various hydrocarbon-compounds.

Adsorption of heavy metals from the aqueous solution using activated biomass from Ulva flexuosa.

The removal of various highly toxic heavy metals from wastewater environment is an important task to improve environment. The biosorption potential of cadmium, cobalt and zinc was evaluated using Ulva flexuosa biomass. The impacts of adsorbent dosage, pH of the medium, contact time, and agitation speed were analyzed. The maximum biosorption potential was reached at pH 4.0, 0.4 g initial biosorbent dosage, contact time 40 min and 30 mg/L initial metal concentration for cadmium, while the other factors were similar to zinc, except 35 min contact time (p < 0.01). The optimum absorption was pH 4, 0.6% adsorbent dosage, after 30 min contact time with the heavy metals and 40 mg/L cobalt concentration. Heavy metal removal efficiency was 94.8 ± 3.3%, 87.5 ± 2.3%, and 90.8 ± 1.4%, for cadmium, cobalt, and zinc, respectively (p < 0.01). The Langmuir constant (R2) was 0.980 for cadmium, 0.838 for cobalt and it was 0.718 for zinc. The present results revealed that the selected acid modified biomass was highly suitable for the adsorption of metal ions such as, Cd2+, Co2+ and Zn2+. The present work revealed the potential application of algal biomass for the removal of various heavy metals from the environment.

Adsorption of brilliant green dye onto activated carbon prepared from cashew nut shell by KOH activation: Studies on equilibrium isotherm.

Activated carbon from cashew nut shell via a potassium hydroxide (KOH) at 600 °C in an N2 atmosphere and their characteristics using FT-IR, XRD, SEM with EDS, and BET analysis was investigated. The cashew nut shell activated carbon obtained by KOH activation with a CNS/KOH ratio of 1:1 at 600 °C (N2 atmosphere) for 2 h had the highest surface area (407.80 m2/g) as compared to other ratio samples. Amongst, CNS/KOH ratios of 1:1 sample are used for the adsorbent, they are effects of contact time, pH, adsorbent dose, and initial dye concentration on brilliant green (BG) removal efficiency were studied. Moreover, the Langmuir and Freundlich adsorption models consisted utilized to affirm the adsorption isotherms. They are, best fitting for BG experimental equilibrium data was achieved with the Langmuir isotherm, giving a maximum BG adsorption capacity of 243.90 mg/g.

Enhanced photocatalytic degradation of organic pollutants by Ag-TiO2 loaded cassava stem activated carbon under sunlight irradiation.

Ag-doped TiO2 and Ag-doped TiO2 loaded cassava stem activated carbon (Ag: TiO2/CSAC) were prepared by sol-gel method and are labelled as AT and AT/CSAC respectively. XRD results confirmed that the anatase-TiO2 and crystalline size are decreased (12.37 nm) through the silver doping and cassava stem activated carbon loading. UV-Vis showed that the AT/CSAC makes a red shift from the absorption edge compared to pure and AT samples and then the band gap is reduced (2.81 eV). The increased surface area (238.51 m2/g) of the AT/CSAC sample through the Ag and CSAC, respectively. The consequences point out that the highest photodegradation efficiency (98.08%) of the TiO2 upon silver doping and cassava stem activated carbon loading samples were brilliant green (BG) under sunlight irradiation.

Improved photodegradation of antibiotics pollutants in wastewaters by advanced oxidation process based on Ni-doped TiO2.

The number of antibiotic compounds in wastewaters has been growing globally due to the covid-19 problem. Using antibiotics to treat the patients would produce larger amounts of these compounds into the environment with negative impacts. Hence, finding out the method for the elimination of toxic organic pollutants as well as antibiotics in water is urgent (In this study, the treatment of antibiotic pollutants including cefalexin (CF) and tetracycline (TC) was investigated by applying the advanced oxidation process based on Ni-doped TiO2 (Ni-TiO2). The characterizations technologies such as XRD, XPS, UV-vis, PL, and PC indicated that Ni doping would improve the photocatalytic performance of TiO2. In the photodegradation experiments, the Ni-TiO2 possessed high photocatalytic degradation efficiencies with 93.6% for CF and 82.5% for TC. Besides, the removal rates of antibiotics after five cycles are higher than 75%, implying excellent stability of Ni-TiO2 photocatalyst. The result from the treatment of wastewater samples revealed that the Ni-TiO2 photocatalytic had good performance for removal of CF and TC at a high level of 88.6 and 80.2%, respectively.

Laser induced plant leaf extract mediated synthesis of CuO nanoparticles and its photocatalytic activity.

Metal nanoparticles furnished by the green synthesis approach have exhibited fascinating attributes owing to their biocompatibility with biomolecules, and their rapid environmentally friendly synthesis. On copper oxide (CuO) nanoparticles, a laser induced bio reduction work has been accomplish using Centella asiatica aqueous extract at room temperature is the pioneer in the field. This synthesis technique is easy, fruitful, eco-friendly, and counterfeit for the size-tunable synthesis of diverse shapes of stable copper nanoparticles. UV-visible spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy - Dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and photodegradation study have astounding properties of regulating the formation, crystalline nature, and morphology of an integrated specimen. Moreover, the obtained copper oxide nanoparticle has the tendency to decrease the absorbance maximum value of methylene blue because of the catalytic activity posed by these nanoparticles on the reduction of methylene blue by Centella asiatica. It has been studied and confirmed by UV-visible spectrophotometer, and it has been recognised as an electron relay effect.