Degradation Of Contaminants In Wastewater Research Articles

Biogenic Green Synthesis of Zinc Oxide Nanoparticles from Defatted Coconut Presscake for Wastewater Treatment

Defatted coconut meat presscake is a by-product of coconut milk production, often discarded or used as low-value products, but has the potential to treat wastewater. This study aimed to characterize zinc oxide nanoparticles (ZnO NPs) synthesized from defatted coconut meat presscake and determine their effect on the degradation of contaminants in wastewater and antibacterial properties. The nanoparticles were synthesized via a co-precipitation method using zinc nitrate as a precursor and defatted coconut meat presscake extract as a reducing agent. The nanoparticles were characterized using FTIR (Fourier Transform Infrared Spectroscopy), FE-SEM (Field-Emission Scanning Electron Microscopy), XRD (X-ray diffraction), and TGA (Thermogravimetric Analysis). The ZnO NPs exhibited a hexagonal wurtzite structure with an average size of 54 nm. The photocatalytic degradation of methylene blue under UV light irradiation showed a degradation efficiency of 79.5% within 180 minutes. Treated wastewater with ZnO NPs at concentrations of 0.5, 1, and 5 mg/L showed a significantly reduced microbial load, with averages of 10.2×106, 8.3×106, and 3.8×106 CFU/mL, respectively, compared to untreated wastewater (16.5×106 CFU/mL), indicating the antimicrobial properties of ZnO NPs. Therefore, ZnO NPs synthesized from defatted coconut meat presscake extract offer an eco-friendly solution for efficiently treating wastewater from the food industry.

A patterned aluminum/reduced graphene oxide/silver sheet for detection and degradation of malachite green in water

A patterned reduced graphene oxide/silver nanoparticles assembled on Al sheet was facilely fabricated using layer-by-layer assembly combined with thermal reduction. The plug-and-play composite sheet shows stable and reproducible performance for SERS detection and catalytic degradation for a toxic malachite green. • A patterned RGO and Ag nanoparticles were facilely assembled on Al sheet. • The sheet was highly active for detection and degradation towards malachite green. • The cost-effective sheet with double functions was stable and reproducible. • The patterned RGO was very significant to the high performance of the sheet. In this work, a patterned reduced graphene oxide (RGO)/silver nanoparticles on Al sheet was prepared using layer-by-layer assembly technique. The morphology, structure and composition of the Al/RGO/Ag were investigated using SEM, XRD and XPS. It showed that there existed a strong interaction among Al, the patterned reduced graphene oxide and Ag nanoparticles in the Al/RGO/Ag sheet, which made the patterned Al/RGO/Ag sheet be as a sensitive SERS material for rapidly monitoring trace malachite green with good reproducibility and high stability. Also, the plug and play Al/RGO/Ag sheet exhibited high and stable catalytic degradation activity for malachite green. The constructed bifunctional sheet will provide some references for designing those materials used in detection and degradation of contaminants in wastewater.

One-step in situ formation of 3D hollow sphere-like V2O5 incorporated Ni3V2O8 hybrids with enhanced photocatalytic performance

3-D hollow sphere-like Ni3V2O8 immobilizing V2O5 nanoparticles were successfully synthesized via in situ recrystallization method without any template. The compact contact between V2O5 and Ni3V2O8 ensuring the photo-inducted carriers fast transport, which would be beneficial for inhibiting recombination rate of electron-hole (e-/h+) pairs. Moreover, the hollow sphere-like structure composed of the smaller nanoparticle could effectively improve of visible light capture capacity (multiple scattering for hollow architectures). Benefiting the synergistic promoting effect of the suitable heterojunction and the fascinating 3D hollow feature, the V2O5@Ni3V2O8 indicated significantly degradation performance when evaluated as photocatalyst for degradation antibiotics and chlorophenols under visible light irradiation. Impressively, the 2-V2O5@Ni3V2O8 heterojunction deliver the optimal degradation efficiency for TC (OTC) and 2,4-DCP (4-CP) were 90.0% (~91.2%) and 92.6% (~90.0%), respectively. The appearance mechanism for the enhancement photocatalytic performance was also elucidated in detail. The facile strategy provides a novel insight into the designing of the photocatalyst with advantages of charges separation and light-harvesting for degradation of contaminants in wastewater.

A novel strategy for acetonitrile wastewater treatment by using a recombinant bacterium with biofilm-forming and nitrile-degrading capability

There is a great need for efficient acetonitrile removal technology in wastewater treatment to reduce the discharge of this pollutant in untreated wastewater. In this study, a nitrilase gene (nit) isolated from a nitrile-degrading bacterium (Rhodococcus rhodochrous BX2) was cloned and transformed into a biofilm-forming bacterium (Bacillus subtilis N4) that expressed the recombinant protein upon isopropylthio-β-galactoside (IPTG) induction. The recombinant bacterium (B. subtilis N4-pHT01-nit) formed strong biofilms and had nitrile-degrading capability. Further testing demonstrated that biofilms formed by B. subtilis N4-pHT01-nit were highly resistant to loading shock from acetonitrile and almost completely degraded the initial concentration of acetonitrile (800 mg L−1) within 24 h in a moving bed biofilm reactor (MBBR) after operation for 35 d. The bacterial composition of the biofilm, identified by high-throughput sequencing, in a reactor in which the B. subtilis N4-pHT01-nit bacterium was introduced indicated that the engineered bacterium was successfully immobilized in the reactor and became dominant genus. This work demonstrates that an engineered bacterium with nitrile-degrading and biofilm-forming capacity can improve the degradation of contaminants in wastewater. This approach offers a novel strategy for enhancing the biological oxidation of toxic pollutants in wastewater.

Influence of parameters on the photocatalytic degradation of phenolic contaminants in wastewater using TiO2/UV system

The photocatalytic degradation of phenol in aqueous suspension using commercial TiO2 powder (Degussa P-25) irradiated with UV light was investigated. Photodegradation was compared using a photocatalyst (TiO2 alone), direct photolysis (UV alone) and TiO2/UV in a single batch reactor with mercury lamp irradiation. The study focused on the influence of various operating parameters on phenol treatment efficiency, including catalyst dosage, initial concentration of phenol, temperature, pH and change in pH were systematically investigated. The highest phenol degradation rate was obtained at pH 9.0, temperature 60°C and catalyst dose of 2 g L−1 with higher mineralization efficiency (in terms of TOC reduction). Experimental results showed that under optimized conditions the phenol removal efficiency was 98% and 100% for the TiO2/UV and TiO2/UV/H2O2 system, respectively. No significant effect on addition of chloride and metal ions was observed. Photodegradation of phenol followed first-order kinetics. To test whether the phenol removal was possible for wastewater using a TiO2/UV system, the degradation study was conducted with the real obtained wastewater. The removal of phenol from obtained wastewater and the synthetic wastewater containing phenol was comparable. The TiO2/UV system developed here is expected to be useful for the treatment of wastewater containing phenol.

Immobilization of Rhodococcus rhodochrous BX2 (an acetonitrile-degrading bacterium) with biofilm-forming bacteria for wastewater treatment

In this study, a unique biofilm consisting of three bacterial strains with high biofilm-forming capability (Bacillus subtilis E2, E3, and N4) and an acetonitrile-degrading bacterium (Rhodococcus rhodochrous BX2) was established for acetonitrile-containing wastewater treatment. The results indicated that this biofilm exhibited strong resistance to acetonitrile loading shock and displayed a typical spatial and structural heterogeneity and completely depleted the initial concentration of acetonitrile (800mgL−1) within 24h in a moving-bed-biofilm reactor (MBBR) after operation for 30days. The immobilization of BX2 cells in the biofilm was confirmed by PCR–DGGE. It has been demonstrated that biofilm-forming bacteria can promote the immobilization of contaminant-degrading bacteria in the biofilms and can subsequently improve the degradation of contaminants in wastewater. This approach offers a novel strategy for enhancing biological oxidation of toxic pollutants in wastewater.