Vol 40, No 4 (2018)

The destruction of GT azo active orange dye in the flow–through plasma–chemical reactor was studied. The impact of the treatment time on the degree of dye decomposition in a plasma torch is studied. It is shown that decomposition of GT azo active dye passes through three stages and results in the formation of compounds possessing good biodegrability.

Antibacterial properties of modified alumosilicates are investigated. It is established the improvement of antimicrobial properties and an increase of the degree of water disinfection to 89–97% in the case of modified sorbents. For all water samples taken in surface water bodies the most efficient results in the decrease of the total microbial number were shown by allumosilicates modified by HCl. Their practical use makes it possible to reduce the total microbial number to the standards of drinking water (50 CFU/cm³).

Herein we present spent black tea as an adsorbent for the removal of Congo red dye from aqueous solutions. The effects of various parameters such as pH, time, temperature, adsorbent dosage and adsorbate dosage on dye adsorption were investigated. Batch experiments were conducted using different amount of adsorbent material (2.5–1000 mg) at varying amounts of adsorbate (5–500 mg/L) at 35°C and different pH (1–13). A maximum dye removal of >80% was achieved with an adsorbent dose of 100 mg, adsorbate concentration of 5 mg/L under pH range of 6 within 5 min at room temperature. The experimental data were modeled by Langmuir, Freundlich and Temkin isotherms and conforms to both Langmuir and Freundlich isotherms but not to Temkin isotherm. The proposed spent black tea can be effectively used as a low cost adsorbent for the removal of Congo red dye.

Polyacrylonitrile/polyamide (PAN/PA) thin film composite nanofiltration membranes were manufactured by interfacial polymerization (IP) of trimesoylchloride reacting with piperazine, in the presence of triethylamine. The influence of IP reaction time up to 100 s on the membrane performance and structure was investigated considering flux, rejection, structural morphology and roughness of the membrane using permeation test, scanning electron microscopy, atomic force microscopy as well as fourier transform infrared spectroscopy. Structural evaluation of membranes revealed that the average PA surface pore size was reduced initially up to 60 s of reaction due to the crosslinking process and PA layer compaction increment, however, became larger at longer reaction times. The PA layer effective thickness grew up with IP time and became constant after 60 s. The best water flux and Na₂SO₄ salt rejection were obtained at 60 s of reaction, which were 100 m³/day and 87% at pressure of 13 barg. Variation trends of permeation and morphological results showed accordance that confirmed their accuracy. Comparison of the Na⁺ rejection value with the rejection of commercialized NF membrane of Dow Company (NF90–400/34i) showed acceptable result for membrane performance.

Optimal conditions for the microextraction concentration and spectrophotometric determination of iodine (I, V, VII) forms as ionic associates of triiodide anions with the cation of astrazone brilliant red 4G dye have been found. A new procedure for the spectrophotometric determination of the total iodine content in drinking and mineral waters with the detection limit of 8.9 μg/dm³ was developed and tested. This procedure is combined with microextraction concentration and meets the requirements of “green” chemistry.

Three nanoparticles’ materials are prepared, characterized and their performance was evaluated for efficient removal of five organochlorine, one organofluorine and six different kinds of bacteria. Gas chromatography/mass spectroscopy have been used to monitor the pesticides concentration before and after treatment by these prepared materials. Graphene gives the most efficient removal of these pesticides than graphene–silver composite but the later is more efficient for remediation of water contaminated with different kinds of bacteria.

The water treatment of aluminum using a wood membrane was shown to be highly effective. It was found out that the highest rejection coefficient of Al(III) in the form of its hydroxo–compounds (up to 99.9%) was observed at pH 6.5–8.1, the initial aluminum concentration up to 125.0 mg/dm³, working pressure 1.0 MPa, the permeate yield up to 70% and the attained level of these ions in drinking water within the maximum permissible concentration (MPC).