Abstract The use of agro-industrial wastes as biosorbents is a promising alternative for sustainable, economical and effective adsorption. However, few studies evaluate the use of Brazilian agro-industrial waste as biosorbents without physicochemical pre-treatment. This study explored the potential of sugarcane bagasse (SCB) and rice husk waste (RHW) as low-cost biosorbents for yellow tartrazine dye removal. Characterization of the materials were carried out using ATR-FTIR, SEM, pHPZC and lignocellulosic composition. Cellulose and hemicellulose were the major constituents of both materials. By the Box-Behnken experimental design, the response surfaces indicated maximum removal of 60.1% for SCB and 83.1% for RHW. While the qmax of SCB and RHW for tartrazine were relatively low at 2.45 ± 0.03 mg g-1 and 3.55 ± 0.02 mg g-1, respectively, the potential for achieving higher dye removals by increasing the adsorbent dosage in large-scale applications warrants further investigation. For both biosorbents, the pseudo-second-order kinetic model and Brouers-Sotolongo isotherm provided the best fit for the data, and the adsorption processes were spontaneous and exothermic. In conclusion, SCB and RHW demonstrated high tartrazine removal, promoting sustainable agro-industrial waste management. agroindustrial agro industrial However pretreatment. pretreatment pre treatment. treatment pre-treatment (SCB (RHW lowcost cost ATRFTIR, ATRFTIR ATR FTIR, FTIR ATR-FTIR SEM composition BoxBehnken Box Behnken design 601 60 1 60.1 831 83 83.1 245 2 45 2.4 003 0 03 0.0 g1 g g- 355 3 55 3.5 002 02 g1, 1, respectively largescale large scale investigation pseudosecondorder pseudo second order BrouersSotolongo Brouers Sotolongo data exothermic conclusion management 6 60. 8 83. 24 4 2. 00 0. 35 5 3.

An experiment was proposed applying the Chemometric approach of Multivariate Analysis for inclusion in undergraduate Chemistry courses to promote and expand the use of this analytical-statistical tool. The experiment entails the determination of the acid dissociation constant of dyes via UV-Vis electronic spectrophotometry. The dyes used show from simple equilibrium to very complex systems involving up to four protolytic species with high spectral overlap. The Chemometric methodology was more efficient than univariate methods. For use in classes, it is up to the teacher to decide which systems should be utilized given the time constraints and laboratory conditions.

The modern stopped-flow reaction analyzer has shown high efficiency and flexibility, which provides outstanding sample economy with a dead-time of less than 1 ms. However the cost of the equipment imposes a serious restriction to many Brazilian scientists and teachers. In this work we describe the construction of a low-cost stopped-flow system coupled to a UV-Vis spectrophotometer. The performance of the system was checked by monitoring the kinetics of two reactions: the fading of phenolphthalein in aqueous alkaline solution and the chlorophyll a demetallation in acid medium. The apparatus showed reasonable efficiency with a dead-time of 0.3 to 0.5 s. The very good results obtained in these two illustrative processes show that the system is satisfactory for determining rate constants with mean reaction times ranging from seconds to minutes.