Evaluation of zinc adsorption through batch and continuous scale applying Bayesian technique for estimate parameters and select model.

This work aims to study the efficiency of zinc adsorption onto granular-activated carbon, predicting the mathematical models that best describe the adsorption behavior in a fixed bed column. First, batch scale experiments were performed to evaluate the influence of pH (3 to 6), contact time (5 to 60 min), and absorbent concentration (5 to 25 g L-1) using synthetic effluent. Fixed bed column experiments were performed by varying the adsorbent concentration (10, 13, 20, and 40 g L-1) and the effluent flow rate (15 and 20 mL min-1). Markov Chain Monte Carlo and Bayesian criteria information were applied to describe the phenomena using Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, Toth, Khan, Radke-Prausnitz, for isotherm models, and Thomas; Yoon-Nelson; Yan; Clark models for breakthrough curve. Adsorption operating best conditions were pH 5, 20 g L-1 of solid, and 50 min of contact time. These parameters allowed 80% of Zn removal, being better described by the Tempki model. In tests on a pilot plant, the Yan model was able to predict the second-order kinetic model, with an increase in the effluent flow and a 50% increase in the bed saturation time with a greater amount of adsorbent solid.

Efficiency evaluation of thermal, ultrasound and solvent techniques in activated carbon regeneration.

The regeneration of diclofenac saturated activated carbon was studied and compared by thermal, solvent and ultrasound techniques in this work. Thermal regeneration was performed at 673 K in atmospheric air for one hour. Different proportions of solvents (ethanol, ethyl acetate and H2O) were used to evaluate the regeneration of the sorbent solid. Ultrasound treatment was tested by varying the time (5 and 15 min) and bath temperature (298 and 323 K). With the highest levels of regeneration for each technique employed, regeneration cycle tests were conducted. With the adsorption capacity recovery limit set at 60%, 8 regeneration cycles were achieved. At the end of the 8th regeneration cycle, the thermal technique made it possible to maintain the adsorption capacity at 75%. Using the water/ethanol (50:50) solvent mixture, after 8 cycles, 64% of solid regeneration was obtained. With the ultrasound technique, in the 5th cycle the solid regeneration capacity was reduced to 65%, remaining constant until 8°. The sorbent solid was characterized by TGA, N2 adsorption, FTIR and sem.

Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.