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2 Ecological Chemistry and Engineering. S

2 2019

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Post-coagulation sludge as an adsorbent of dyes from aqueous solutions

Pieczykolan Barbara, Płonka Izabela

Ecological Chemistry and Engineering. S

2019

Vol. 26, nr 3

509--520

The main source of usable water supply in Poland is surface water. The most frequently used methods of surface water treatment are coagulation and filtration processes. During these processes post-coagulation sludge is generated, which is the main waste produced in water treatment plants. This sludge is characterized by an amorphous structure with a strongly developed specific surface, similar to sewage sludge. Dried and crushed post-coagulation sludge was used in the studies as an adsorbent of two acid dyes: Acid Red 18 (AR 18) and Acid Green 16 (AG 16). The most favourable pH of process and contact time as well as sorption isotherm were established. For both dyes the most favourable pH value was equal 2. The tests showed that in the case of AR 18 (180 min) a longer contact time was necessary to reach the equilibrium than for AG 16 (120 min). Moreover, based on the different isotherm two-parameter models, the sorption capacity, type of sorption and energy of sorption were calculated based on linear and non-linear regression. The tests showed that in the case of dye AG 16 monolayer sorption occurred - the analysis showed better fitting the results to Langmuir model. Moreover, for both dyes, physical adsorption took place - it was indicated by the values of parameter 1/n (computed from the Freundlich model).

Application of excess activated sludge as waste sorbent for dyes removal from their aqueous solutions

Pieczykolan Barbara, Płonka Izabela

Ecological Chemistry and Engineering. S

2019

Vol. 26, nr 4

773--784

Organic dyes are widely used in many industries (textiles, food, cosmetics, medicine and biology). These plants produce wastewater containing dyes. Even small amounts of dyes can cause a strong colour of wastewater. Therefore, it is very important to effectively remove residues of these pollutants from the wastewater, before discharging them into the environment. The sorption process is one of the methods used to remove dyes. However this method is often unprofitable economically in comparison with other dye removal processes, due to the high cost of commercial sorbents. Therefore, research is currently conducted in order to find waste materials that can be used as sorbents. The static sorption process of two dyes were carried out (Acid Red 18 and Acid Green 16) with the use of dried excess sludge. The activated sludge (excess) came from a municipal sewage treatment plant that purifies wastewater from carbon, nitrogen and phosphorus compounds. During the study the most favourable pH of the process and the contact time of the sorbent with the dyes were determined. It was observed that for both dyes the highest effectiveness of dye removal was obtained at pH = 2. The most favourable contact time was equal to 60 and 180 minutes for Acid Red 18 and Acid Green 16 respectively. In addition, in order to establish process parameters, a different models of sorption isotherm was examined. The studies showed that the sorption capacity (calculated based on Langmuir model) was much higher in the case of Acid Green 16 (qm = 434.8 mg/g) than for Acid Red 18 (qm = 109.9 mg/g). The experiments to evaluate the effect of pH, contact time on the process effectiveness and to determine the sorption isotherm were conducted at 293.15 K.