This work describes the development of an automatic titrometric method in flow-batch with potentiometric detection using alternative and easily accessible materials. Arduino board and its modules, solenoid valves to control the flow rate, peristaltic pump to propel and suction fluids and tubes of inert material to connect the different parts of the Flow-Batch Analyser (FBA) were used. The use of solenoid valves controlled by microcontrollers proved to be efficient for controlling the flow in FBA systems, the correlations of their flow rates as a function of time showed good linearity with correlation coefficients (r) 0.9994 and 0.9997 for the valve 1 and valve 2, respectively, allowing correct addition of pre-established volumes. Accuracy was verified by comparing the results of the proposed method with the classic potentiometric titration with statistically evaluated by Student’s t-test in NaOH with HCl and vinegar with NaOH titrations. Results confirmed the efficiency to use Arduino board and its modules and automatic titrometric method in flow-batch developed in this work allow the implementation of practical disciplines, such as potentiometric titration and flow analysis system in undergraduate courses, making these instruments more accessible, especially for the chemistry students.

This work describes the development of a peristaltic pump and a photometric detector, using “Arduino” and alternative and low-cost materials for flow analysis system. The analytical calibration curve of the acid-red-283 using the proposed system presents 0.9984 and 3.9% as the coefficients of determination and variation, and 1.1 and 3.8 mg L-1 as limits of detection and quantification, respectively. Three prepared samples of the acid-red-283 (25, 30 and 35 mg L-1) showed recovery between 99 to 104%. For construction of the peristaltic pump and the photometer using Light Emitting Diodes (LED), light-dependent resistor (LDR) were spent less than 10% of the cost was spent on a commercial system employing a peristaltic pump and a spectrophotometer. Furthermore, the peristaltic pump and the photometer developed in this work allow the implementation of practical disciplines, such as molecular absorption spectrophotometry and flow analysis system in undergraduate courses, making these instruments more accessible, especially for the chemistry students.

No processo de produção do etanol a vinhaça é um subproduto gerado em grande escala, em média, na razão de aproximadamente 13 L de vinhaça por litro de álcool destilado. Este volume produzido representa um problema no acondicionamento e nos processos de tratamento deste efluente que, na maioria das vezes, é lançado no solo por fertirrigação. Tendo em vista os altos teores de nutrientes, com destaque para o potássio e o alto teor de matéria orgânica, a disposição da vinhaça no solo necessita de estudos, uma vez que pode ocorrer lixiviação de vários desses elementos às águas subsuperficiais. Foram realizados ensaios de batelada, o que permitiu a avaliação do efeito de diferentes fatores, como a variação da razão solo: solução e do tempo de contato na sorção do potássio em três amostras de solo distintas, submetidas à aplicação de vinhaça. Nos ensaios com razão solo:solução 1:50; em todas as amostras, houve maior sorção que na razão 1:4. O tempo de contato ideal para estabelecimento das condições de equilíbrio foi 24 h. Dentre as amostras estudadas a maior sorção foi constatada para a amostra com maior percentual de argila em sua composição e maior capacidade de troca catiônica.

In the process of producing ethanol, vinasse is a by-product generated in large scale, on average, at a rate around 13 L of vinasse per liter of distilled alcohol. This volume represents a problem in conditioning and treatment processes of this wastewater, which most of time is incorporated into the soil by fertigation. Considering the high levels of nutrients, especially potassium and the high content of organic matter, the disposal of vinasse into the soil needs further studies, because there may be leaching of several elements to groundwater. Batch tests were performed, which allowed assessment of the effect of different factors such as variation of the soil to solution ratio and the variation of contact time between soil and solution to evaluate the mobility of potassium in three different soil samples. The results showed that in the tests with the soil:solution ratio of 1:50, in all samples, the sorption was greater than with the ratio 1:4. The ideal contact time for establishment of equilibrium conditions was 24 h. The sample with higher percentage of clay and higher cation exchange capacity demonstrated the highest sorption of potassium.