Evaluation of the chromium bioavailability in tanned leather shavings using the SM&T sequential extractions scheme

Abstract

Tanned leather shavings from Brazilian tanneries were analysed in order to assess the chromium extractability and bioavailability, and consequently its potential release into other environmental compartments when the shavings are deposited on landfill sites. The conventional SM&T (Standard, Measurement and Testing Programme) sequential extractions scheme was applied. Also, Cr(VI) and Cr(III) concentrations in the oxidizable fraction were determined. The results indicated high total chromium concentrations (1.04, 1.46 and 2.74%) in the samples A, B and C, respectively. A significant quantity of chromium (about 6 -11% of total chromium) was easily released in slightly acidic conditions (step 1). This fraction is the most labile, and therefore the most dangerous and bioavailable for the surrounding environment. Less chromium (1 -3% of total chromium) was released in reducing conditions (step 2), whereas about 0.5 -3% of total chromium was strongly associated to the leather shaving structure (residual fraction -step 4), and therefore, its release under environmental conditions would be unlikely. Most of chromium (about 83 -92% of the total chromium) was bound to the organic matter, as expected, since it was released in oxidizing condition (step 3). Part of chromium released in this fraction was also converted into Cr(VI), which is more labile and toxic than Cr(III). Considering the chromium concentrations, the sequentially extracted fractions may be ordered as follows: oxidizable4exchangeable4reducible4residual.

Adsorption mechanism of Cr(VI) onto GO/PAMAMs composites

“…The influence of temperature on the thermodynamic parameters is related to the adsorption process. Several thermodynamic parameters were calculated according to Eqs (9) and (10) 31 .where K 0 is the adsorption distribution coefficient, which was determined from the intercept of plotting ln( q e / C e ) versus C e at different temperature by extroplotting C e to zero according to Khan and Singh method 1 , and Δ H 0 is the standard enthalpy change (J·mol −1 ), Δ S 0 is the standard entropy change (J·mol −1 ·K −1 ), Δ G 0 is the standard Gibbs free energy change, R is the gas constant (8.314 J·mol −1 ·K −1 ) and T is the absolute temperature in Kelvin (K), respectively. Δ H 0 and Δ S 0 were obtained from the slope and intercept in the curve of ln K 0 versus T −1 .…”

“…Chromium is widely used in the industries of leather-tanning 1 , mining, textile dyeing, manufacturing processes of anti-corrosion agents and pigments 2 , which means that it’s unavoidable to generate large amounts of chromium-containing wastewater. As is known that hexavalent [Cr(VI)] and trivalent [Cr(III)] are the most stable forms in aquatic environment and Cr(VI) is about 1000 times more poisonous than Cr(III) 3 .…”

Rumex abyssinicus (mekmeko): A newer alternative for leather manufacture

“…Leather manufacture involves the following unit processes viz., soaking, liming, deliming, pickling, tanning, post‐tanning, and finishing, where tanning is considered as one of the important process, 3 that protects the leather against environmental effects such as microbial degradation, heat, sweat, or moisture 4 . Vegetable tanning is the oldest tanning process in the leather sector, even though chrome tanning has gained prominence in leather manufacture ever since its discovery by Prof. Knap in 1858 5…”

“…Leather manufacture involves the following unit processes viz., soaking, liming, deliming, pickling, tanning, post-tanning, and finishing, where tanning is considered as one of the important process, 3 that protects the leather against environmental effects such as microbial degradation, heat, sweat, or moisture. 4 Vegetable tanning is the oldest tanning process in the leather sector, even though chrome tanning has gained prominence in leather manufacture ever since its discovery by Prof. Knap in 1858. 5 Today 90% of leather is manufactured using chrome tanning system mainly due to its high stability to wet heat with a shrinkage temperature of about 110 C, but the chrome tanning agent is under constant scrutiny due to low uptake of Cr(III) salts which is released in tannery effluent, and also exposure of Chromium bearing wastewater is harmful to human beings and animals, because of the biotoxicity of Cr(III) salts under certain ligand environment.…”

Preparation of Fe3O4@SiO2@ P(AANa-co-AM) Composites and Their Adsorption for Pb(II)

“…K 0 was obtained from the intercept of plotting ln(q e /C e ) versus C e at three different temperatures by extrapolating C e to zero according to the Singh and Khan method. 34 ΔH 0 and ΔS 0 were obtained from the slope and intercept in the curve of ln K 0 versus T −1 . The values of ln K 0 , ΔH 0 , ΔS 0 , and ΔG 0 are listed in Table 4.…”