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The Use of Coconut Shells for the Removal of Dyes from Aqueous Solutions

Jóźwiak T., Filipkowska U., Bugajska P., Kalkowski T.

Journal of Ecological Engineering

2018

Vol. 19, nr 4

129--135

The main purpose of the work was to check the possibility of using coconut shells for the removal of the dyes popular in the textile industry from aqueous solutions. The sorption abilities of an unconventional sorbent were tested against four anionic dyes: Reactive Black 5, Reactive Yellow 84, Acid Yellow 23, Acid Red 18 as well as two cationic dyes: Basic Violet 10 and Basic Red 46. The scope of research included investigation pertaining to the effect of pH on the effectiveness of sorption of dyes, conducted in order to determine the time of equilibrium of sorption and determine the maximum sorption capacity of coconut shells with respect to pigments. The most favorable pH of sorption for the anionic dyes and Basic Violet 10 was pH 3 and for Basic Red 46 – pH 6. The equilibrium time of sorption was the shortest in the case of acidic dyes (Acid Yellow 23/ Acid Red 18 – 45 min), while the longest in the case of alkaline dyes (Basic Red 46 – 90 min, Basic Violet 10 – 180 min). The sorption capacity of coconut shells in relation to anionic dyes was for Reactive Black 5 – 0.82 mg/g, Reactive Yellow 84 – 0.96 mg/g, Acid Yellow 23 – 0.53 mg/g and for Acid Red 18 – 0.66 mg/g. The tested sorbent showed much higher sorption capacity with respect to the cationic dyes, i.e. Basic Violet 10 (28.54 mg/g) and Basic Red 46 (68.52 mg/g).

Zdolności adsorpcyjne kaolinu wobec barwników kationowych i anionowych

Ziółkowska D., Shyichuk A.

Inżynieria i Ochrona Środowiska

2007

T. 10, nr 1

59-70

Przemysłowy kaolin (surowy oraz modyfikowany chemicznie bądź termicznie) poddano badaniom pod kątem jego przydatności jako ekonomicznego adsorbentu stosowanego do usuwania zarówno barwników kationowych, tj. błękitu metylenowego, czerwieni anilanowej GRL i zieleni malachitowej, jak również barwników anionowych, tj. pąsu kwasowego 4R i zieleni kwasowej czystej V, z roztworów wodnych. Izotermy adsorpcji wyznaczono metodą statyczną w temperaturze pokojowej. Kaolin niemodyfikowany w porównaniu z innymi kaolinami okazał się skutecznym adsorbentem dla barwników kationowych, osiągając wartości maksymalnej adsorpcji w zakresie 13+30 mg/g. Wykazano, że wielkość adsorpcji barwników o stosunkowo małych cząsteczkach (błękit metylenowy) można zwiększyć poprzez przemywanie adsorbentu zasadą, a barwników azowych (czerwień anilanowa GRL) - poprzez obróbkę kaolinu kwasem. Stwierdzono, iż kaolin przemysłowy wygrzewany w temperaturze 750°C może adsorbować niektóre barwniki anionowe.

An industrial kaolin was modified by chemical treating, i.e. by washing with HSO4 or NaOH Solutions, as well as by calcination at 750°C. Both raw and modified kaolin samples were examined as economic adsorbents employed for elimination of three cationic dyes (methylene blue, basic red 46 and basic green 4) as well as two anionic dyes (acid red 18 and acid green 16) from aqueous Solutions. The adsorption isotherms were determined with batch method at the room temperature. Yalues of parameters of Langmuir and Freundlich equations as well as proportional process efficiency have been calculated for all the adsorption systems. Non-modified kaolin appeared to be an effective adsorbent for cationic dyes. Values of adsorption capacity for these adsorbates are contained in the range: 12.6 mg/g (methylene blue) to about 30 mg/g (basic red 46). It was proved that adsorption of methylene blue from the solutions of high concentrations increases after washing of the adsorbent with basic. In this case new adsorption sites probably originate as a result of zeolitization and are accessible only for relatively small dye molecules. Adsorption of azodyes (basic red 46) increases as a consequence of treating of the kaolin sample with acid. Then, calcination of the adsorbent make it almost inactive towards most of examined cationic dyes. When initial dye concentration is equal 20 mg/dm3 and raw kaolin dose amounts 1 g/dm3 obtained decolorization degree of solutions is contained in the range from 46.9% (basic red 46) to 85.6% (methylene blue). Process efficiency for basic red 46 can be additionally improved by 14% as a result of washing of adsorbent with acid. Moreover it was stated that raw industrial kaolin does not adsorb anionic dyes. However, in consequence of heating at 750°C crystalline lattice of the adsorbent disintegrates and amorphous silica as well as aluminum oxide appear. Thanks to the mentioned process the calcined mineral shows affinity for some anionic dyes (acid green 16).