A new method for assessment of the sludge disintegration degree with the use of differential centrifugal sedimentation.

A novel method for assessing the disintegration degree (DD) of waste activated sludge (WAS) with the use of differential centrifugal sedimentation method (DCS) was shown herein. The method was validated for a WAS sample at four levels of disintegration in the range of 14.4-82.6% corresponding to the median particle size range of 8.5-1.6 µm. From the several sludge disintegration methods used (i.e. microwave, alkalization, ultrasounds and peroxydisulfate activated by ultrasounds), the activated peroxydisulfate disintegration resulted in the greatest DD 83% and the smallest median particle size of WAS. Particle size distribution of pretreated sludge, measured by DCS, was in a negative correlation with the DD, determined from soluble chemical oxygen demand (SCOD; determination coefficient of 0.995). Based on the obtained results, it may be concluded that the DCS analysis can approximate the WAS disintegration degree.

Green synthesis of gold nanoparticles using Artemisia dracunculus extract: control of the shape and size by varying synthesis conditions.

In this study, selective green synthesis of gold nanoparticles (nAu) with the use of Tarragon extract (Artemisia dracunculus) was investigated. Characterization of the synthetized nAu was carried out using several techniques including: UV-Vis, SEM, zeta potential analysis, DLS, and ATR-FTIR. Based on measurements of Tarragon extract by HPLC-MS, significant chemical substances participating as reducing and stabilizing agents were identified. FTIR confirmed typical functional groups that could be found in these acids on the nAu surface, such as O-H, C=O and C-O. The effects of various parameters (concentration of Tarragon extract, Au precursor, and initial pH of the synthesis) on the shape and size of the nanoparticles have been investigated. UV-Vis and SEM confirmed the formation of nAu at various concentrations of the extract and Au precursor and showed correlation between the added extract concentration and shift in maximal absorbance towards higher frequencies, indicating the formation of smaller nanoplates. Zeta potential determined at various pH levels revealed that its value decreased with pH, but for all experiments in the pH range of 2.8 to 5.0, the value is below - 30 mV, an absolute value high enough for long-term nAu stability. In order to evaluate nAu catalytic activity, the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model system. The reaction takes place 1.5 times faster on Au-triangles than on Au-spherical NPs.

Modification of a hollow-fibre polyethersulfone membrane using silver nanoparticles formed in situ for biofouling prevention.

Biofouling represents a serious problem limiting the widespread application of membrane technology. Therefore, the aim of this study was to develop and verify a new modification method based on the in situ formation of silver nanoparticles and their incorporation into a membrane polymer to prevent biofouling. The modification method consisted of soaking a commercial hollow-fibre polyethersulfone membrane in a solution of silver ions, diffusion of ions into the membrane polymer, and their reduction using ascorbic acid. Such a modified membrane displayed a lower tendency towards biofouling, exhibiting an about 15% higher permeability compared to an unmodified membrane when filtering actual wastewater treatment plant effluent. The modification also led to the formation of stable silver nanoparticles (mostly in the range of 25-50 nm) homogenously distributed on the surface of the hollow-fibres. This resulted in higher surface hydrophilicity (the water contact angle decreased from 91° to 86°) contributing to the biofouling prevention. The modified membrane also showed high stability, as only 2.1% of the total silver leached after 8 h of filtration. Moreover, no changes in the original membrane cross-section structure or separation properties were observed. Besides the improved antibiofouling properties of the modified membrane, the main advantage of the developed method is its simplicity, short reaction time, absence of high energy-consuming initiation, and the possibility to apply it on site, thus even with commercial membrane modules. It will increase the application potential of membranes in the field of wastewater treatment.