DOI: 10.3303/CET25117126 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 8 December 2024; Revised: 30 March 2025; Accepted: 17 May 2025 
Please cite this article as: Salmi O., Pastori F., Marinsalta M., Zola L., Rossi F., Masi M., 2025, Powertan: a Revolution for the Tanning Leather 
Sector, Chemical Engineering Transactions, 117, 751-756  DOI:10.3303/CET25117126 
  

CHEMICAL ENGINEERING TRANSACTIONS 

VOL. 117, 2025 

A publication of 

The Italian Association 
of Chemical Engineering 
Online at www.cetjournal.it 

Guest Editors: Fabrizio Bezzo, Flavio Manenti, Gabriele Pannocchia, Almerinda di Benedetto 

Copyright © 2025, AIDIC Servizi S.r.l. 

ISBN 979-12-81206-17-5; ISSN 2283-9216 

Powertan: a Revolution for the Tanning Leather Sector 

Omar Salmi, Fabio Pastori, Marco Marinsalta, Luca Zola, Filippo Rossi, Maurizio 

Masi* 

Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano, Piazza Leonardo de Vinci 32, 

20133 Milan, Italy 

maurizio.masi@polimi.it 

Powertan is a disrupting new approach for leather tanning were the penetration inside the hide to be tanned is 

enhanced by the use of an externally applied electric field. Thus, the penetration is no longer controlled by the 

fickian diffusion mechanism by ion migration.The result is a dramatical decrease of the process time, from the 

almost 24 h of the traditional drum operation to few minutes. Moreover, the electric field reduces the necessity 

of ancillary operations like the pickling and the basification with a reduction to about one tenth of the bath/leather 

ratio from the about 20 L/kg. Here, the first small scale batch tests will be presented with a preliminar modeling 

interpretation. 

1. Introduction

Leather is an extremely valuable natural product with applications across a large number of sectors, from shoes 

and dress fashion to automotive and furniture (Král et al., 2014). It is the tenth most traded commodity, with a 

total value of about USD 440 billion in 2022 (Fortune 2023). Its market is estimated to grow further with a 

compound annual growth rate (CAGR) of 6.2 % until 2030 (Acumen 2023). Its use by humankind dates to 

ancient times and it can be viewed as the first example of circular economy product because the raw material 

is actually a waste product from the food industry (Kesarwani et al., 2015). Accordingly, the leather market is 

the number one by-product market (UNIC 2023). 

The fundamental step in the process of transforming the raw material into a finished product is tanning, i.e. the 

stable penetration into the hide of substances that fix the collagen fibres to prevent its putrefaction, (Covington, 

2009). In the absence of tanning, the skin, being of natural origin, would degrade within a few days, making its 

further uses impossible (Muralidharan et al., 2021). The rudimental system to limit the putrefaction was primarily 

by drying, but it is with the introduction of the vegetal tannins treatment, that humans discovered the leather (a 

stabilized raw skin) (Auad et al., 2019). Tannins, as polyphenols, interact with collagen by some weak 

interactions like 𝐻 − bonds and improve the hydrothermal/rot resistance of it (Carçote et al., 2016). After long 

time, at the end of XIX century it was discovered the extraordinary stabilization effect of 𝐶𝑟(𝐼𝐼𝐼) salts that today 

is used to produce almost the 80 % of leather (ICDA, 2024).  

To facilitate the diffusion of 𝐶𝑟, the solubility and the stability in solution, chromium basic sulphate 𝐶𝑟𝑂𝐻𝑆𝑂4 is 

used coupled with a previous acidic treatment (pickling) (Yang et al., 2022). The use of 𝐶𝑟𝑂𝐻𝑆𝑂4 produces the 

highest quality of the final product from the consumers point of view at the lower costs. 𝐶𝑟(𝐼𝐼𝐼) has the highest 

affinity to the carboxyl groups of collagen chains (the hide constituents) through the olation reaction (Covington 

2009). 

Tanning is preceded the pickling step where the hide is immersed in an acid solution to facilitate the 𝐶𝑟(𝐼𝐼𝐼) ions 

penetration during tanning: a 𝑝𝐻 < 2.8 is needed to avoid the olation reaction. After the addition of the desired 

amount of tanning agent, the 𝑝𝐻 value is then increased, in the so-called basification step, to about 𝑝𝐻 = 3.3 to 

stably fix the 𝐶𝑟(𝐼𝐼𝐼) to the collagen (Biškauskaitė et al., 2021). If these steps are not operated in the right 

sequence (acidification, tanning, basification) the result is a very slow penetration of 𝐶𝑟(𝐼𝐼𝐼) ions because 

diffusion has to compete with the chemical reaction, with the results of a significant increase of the time of 

751

mailto:maurizio.masi@polimi.it


operation coupled with the difficulty of reaching the desired 𝐶𝑟(𝐼𝐼𝐼) content to stabilize all the collagen carboxylic 

moieties. 

In summary, with reference to Figure 1 (Panduranga Rao et al., 1995; Rossi et al., 2015), the leather structure 

and the chemical reaction engineering phenomena related to chromium tanning are: 

− Leather structure is represented as a fibre bundle of collagen originating macro pores, with a 

macroporosity 𝜀𝑝 ≈ 0.2 ÷ 0.3. 

− All pore channels exposed the collagen −𝐶𝑂𝑂𝐻 groups available to react with tanning agent, 𝐶𝑟(𝐼𝐼𝐼). 

− 𝐶𝑟 ions move within the pores reacting (i.e., adsorption like) with the carboxyl groups. Reaction rate is 

function of solution 𝑝𝐻. 

Accordingly, the phenomena involved in the tanning process are: 

− Soaking of the leather to reach enough humidity entrapped in the pores. 

− Adsorption/desorption of the substance to/from the collagen fibres. 

− Diffusion/migrations of the ions along the macropore filled with water. 

 

  
Figure 1: (left) leather structure as a bundle of fibres creating a macropore network; (right) sketch of the ion 

migration within the pore with chemical interaction with surface carboxyl groups of collagen fibres, with a 

behaviour similar to the ethosuximide (ESM) in a partitioning mode. 

 

The idea of applying an electric field to accelerate the tanning process takes inspiration from the work done on 

the vitrification by immobilization in gel of nuclides (Masi et al., 2013). Being conceptually the vitreous gel and 

the hide similar in structure, the substantial speedup of the tanning process was expected as described by 

literature (Masi et al., 2019). 

Overall, the aim of this work is to illustrate the experimental work done at laboratory scale as well as to give a 

first theorical explanation of the process kinetics.  

2. Experimental set up 

A laboratory scale electrochemical cell, illustrated in Figure 2, where the hide to be tanned is placed as a porous 

septum separating the cathodic (-) and the anodic (+) compartments. The cell exposed a hide of 

50 𝑥 50 𝑥 1.5 𝑚𝑚3and the tank volume is 𝑉𝐿 = 0.08 𝐿. Two carbon felts are introduced in contact with the leather 

and the electrodes to better distribute the tanning solution and the electric current. From the electrochemical 

point of view this is a zero-gap cell. 

 

  
Figure 2: (left) sketch of the electrochemical cell structure with the hide to be tanned placed as the usual 

membrane separating the anodic and the cathodic compartments. (right) a picture of the whole system with 

highlighted the cell. 

 

Continuously controlled variables were 𝑝𝐻, temperature, applied potential ∆𝑉 and electric current 𝐼, while the 

cell is operated in a potentiostatic mode. Stepwise controlled variables were the tanning solution composition 

(𝐶𝑟(𝐼𝐼𝐼) and 𝐶𝑟(𝑉𝐼)), leather composition (𝐶𝑟(𝐼𝐼𝐼) and 𝐶𝑟(𝑉𝐼)) and shrinking temperature 𝑇𝑠 after basification. 

+-

le
a
th

e
r

makeup

c
a
rb

o
n
 f

e
lt

752



The applied voltage was always kept below ∆𝑉 = 2 𝑉, actually in operation below ∆𝑉 = 1.2 𝑉, because two main 

constrains: to avoid water electrolysis (∆𝑉𝐻2𝑂 = 1.23 𝑉) and the oxidation of 𝐶𝑟(𝐼𝐼𝐼) to 𝐶𝑟(𝑉𝐼) (∆𝑉𝐶𝑟 = 1.38 𝑉, in 

acidic conditions) (Kerr, 2000). As it will be demonstrated below, the 𝐶𝑟(𝐼𝐼𝐼) penetration is determined by 

migration, thus the 𝐶𝑟(𝐼𝐼𝐼) flux is substantially unidirectional from the anode to the cathode. Therefore, was it 

not necessary to differentiate the composition in the two cell compartments with a significant simplification of 

the cell design. 

2.1 Materials and Methods 

The analyses are carried out on three batches of pickled hides, stored in a conservative pickling solution, coming 

from young cow. They are supplied directly by the tannery BCN Concerie S.p.A. (Santa Croce sull’Arno, Italy). 

Despite the different batches do not show obvious differences, it is important to consider that the various pieces 

of hide are taken from different parts of the animal, which can impact on the dispersion of the results. 

The solvents and reactants employed in analyses are: Acetic acid (CAS: 64-19-7, Fisher Scientific, UK), Acetone 

(CAS: 67-64-1, Carlo Erba Reagents, France), Chromosal B (CAS: 12336-95-7, Lanxess, Deutschland), 

Chrome FD (CAS: 12336-95-7, River Chimica Industriale, Italy) Pickel solution (% means w/w of product under 

100 g of raw hide, 40 %of water, 7-8 % NaCl,1 % NaClO2, 0.5 % HCOOH, 1.3 % H2SO4; BCN Concerie, Italy), 

n-hexanol (CAS: 110-54-3, Carlo Erba Reagents, France), Sulphuric acid (CAS: 7664-93-9, Carlo Erba 

Reagents, France), Phosphoric acid (CAS: 7664-38-2, Carlo Erba Reagents,  France), Potassium dichromate 

(CAS: 7778-50-9, Carlo Erba Reagents, France), dipotassium hydrogenphosphate (CAS: 16788-57-1, Carlo 

Erba Reagents, France), 1,5-diphenylcarbazide (CAS: 205-403-7, Carlo Erba Reagents, France), Sodium 

bicarbonate (CAS: 144-55-8, Solvay, Italy). 

The study is mainly conducted using the electrochemical cell described above. 

Once the tanning process is completed, the leather samples are treated following ISO standards for sample 

preparation and analyses required for data collection. The major instrumentation used for the analysis and 

quantification of chromium in leather and in solution are: in case of the total metal analysis, ICP-OES, in case 

of the hexavalent one, UV-Vis following ISO 11083:1994 and ISO 17075-1:2017, while for the shrinkage 

temperature, a shrinkage temperature meter is used, following ISO 3380:2015, and as a cross-analysis, 

Differential Scanning Calorimetry (DSC) is employed. Finally, for the microscopic study of the leather, a 

Scanning Electron Microscope Energy-dispersive X-ray spectroscopy (SEM-EDX) is used. In the end, the 

calculations regarding the exhaustion of the tanning solution were carried out considering the solution before 

and after the tanning process, while the measurement of chromium in the leather was made after the basification 

process. 

3. Experimental results 

More than 400 experimental tests were performed so far exploring the applied potential (∆𝑉 = 0 ÷ 2 𝑉), solution 

concentration (𝐶𝐿,𝐶𝑟
0 = 700 ÷ 40,000 𝑚𝑔/𝐿), process time (𝑡 = 30 ÷ 2400 𝑠), solution recirculation flow rate (𝑄𝐿 =

5 ÷ 40 𝑚𝐿/𝑚𝑖𝑛). The reference recipe used a bath concentration with Chromosal B at 8 %, a recirculation flow 

rate 𝑄𝐿 = 10 𝑚𝐿/𝑚𝑖𝑛 and an applied potential ∆𝑉 = 1 𝑉. After, the tanned leather was basified for 1 ℎ at 𝑝𝐻 =

3.6 and then let rest for 12 ℎ before mechanically and chemically test it. The chromium content in the leather 𝛤𝑖 

was both directly measured on the final product and through the variation of solution composition, i.e., 

𝑉𝐿(𝐶𝐿,𝐶𝑟
0 − 𝐶𝐿,𝐶𝑟) = 𝑚𝑝𝛤𝑖, being 𝑚𝑝 the mass of the sample. 

Figure 3 shows the comparison with the same exposure time and bath composition of the same leather in the 

absence and presence of an applied electric field. It can be easily seen the difference in aspect chromium 

penetrated into the hide by the different blue color. To confirm the visual appearance, the leather tanned with 

the application of the electric field was subjected to SEM-EDX analysis, to visualize the 𝐶𝑟 profile along the 

leather thickness. It can be observed the almost uniform concentration profile within the leather thickness 

demonstrating the high quality of the penetration. 

For sake of the available space, we will here discuss mainly the effect of the electric field on the tanning at 

constant bath composition. Bath concentration and applied potential are the real effective process parameter. 

As it can be easily forecasted the influence of the recirculation flow rate is almost negligible. 

As shown in Figure 4(a), the increase of the applied voltage increases the speed of the tanning process in an 

almost monotone manner. Tests performed by an applied electric potential showed almost the same asymptotic 

concentration, e.g, about 18,000 𝑚𝑔/𝑘𝑔, value that primarily depends on the concentration of the tanning bath. 

The applied voltage directly influences the time necessary to reach asymptotic value. From a macroscopic point 

of view, only the application of about 1 𝑉 leads to a full tanning in about 2 𝑚𝑖𝑛. It is relevant to consider that a 

typical tanning time approaching the 24 ℎ. 

 

753



 
leather thickness

 

Figure 3. (left) same leather exposed and not the electric field under the reference recipes for an exposure 

of 300 𝑠; (right) 𝐶𝑟 profile within the leather thickness measure by SEM-EDX 

4. Modelling 

The total amount of chromium ions in leather is the sum of that contained in the macropores and that linked with 

collagen. Being 𝜀𝑝 the volumetric fraction of macropores and 𝜌𝑝 = (1 − 𝜀𝑝 )𝜌𝑐 the apparent density of leather, 

the total concentration (in 𝑚𝑜𝑙/𝑚𝑝
3) is 𝐶𝐶𝑟

𝑡𝑜𝑡 = 𝜀𝑝𝐶𝑝,𝐶𝑟 + 𝜌𝑝𝛤𝐶𝑟 . The amount of the chromium linked to collagen is 

directly proportional to the concentration in the macropores with a behaviour similar to and adsorption isotherm 

with a saturation value 𝛤𝐶𝑟
∞: 

𝛤𝐶𝑟 = 𝛤𝐶𝑟
∞

𝑏𝐶𝑟𝐶𝑝,𝐶𝑟

1 + 𝑏𝐶𝑟𝐶𝑝,𝐶𝑟 + 𝑏𝐻𝐶𝑝,𝐻
= 𝛤𝐶𝑟

∞
𝑏𝐶𝑟𝐶𝑝,𝐶𝑟

1 + 𝑏𝐶𝑟𝐶𝑝,𝐶𝑟 + 𝑏𝐻10−𝑝𝐻 ≈ 𝐾𝑒𝑞  𝐶𝑝,𝐶𝑟 ≈
𝑑Γ

𝑑𝐶𝑝,𝐶𝑟  
𝐶𝑝,𝐶𝑟 (1) 

where 𝛤𝐶𝑟, 𝑏𝐶𝑟 and 𝐶𝑝,𝐶𝑟 are the adsorbed concentration (𝑚𝑔/𝑘𝑔), the adsorption constant (𝑚3/𝑘𝑔) and the 

concentration in the liquid phase contained in the macropores (𝑚𝑔/𝑚3 ), respectively. As a first approximation, 

to obtain analytical solutions the adsorption isotherm can be also linearized aa shown in eq. (1). 

The model was derived under the approximation of linear drop of electric potential 𝑉 within leather (Ohm’s law), 

with negligible decay in solutions: 

𝜕𝑉

𝜕𝑥
=

𝑗

𝜎𝑝
≈

∆𝑉𝑝

𝐿𝑝
and

𝜕2𝑉

𝜕𝑥2 = 0  (2) 

In not dimensional spatial coordinates within leather 𝑧 = 𝑥/𝐿𝑝, 𝑧 = [0,1] and introducing the characteristic times 

for migration 𝜏𝑀 (i.e., the transport under the effect of electric potential) and for diffusion 𝜏𝐷 (i.e., the transport 

under the effect of concentration gradient) the mass conservation equation within the leather pores takes the 

form: 

𝜕𝐶𝑝,𝐶𝑟

𝜕𝑡
=

1

𝜏𝐷

𝜕2𝐶𝑝,𝐶𝑟

𝜕𝑧2 +
1

𝜏𝑀

𝜕𝐶𝑝,𝐶𝑟

𝜕𝑧
 (3) 

𝜏𝐷 =
𝐿𝑝

2 𝜏𝑝(𝜀𝑝 + 𝜌𝑝𝐾𝑒𝑞)

𝜀𝑝𝐷𝑖
 (4) 

𝜏𝑀 =
𝐿𝑝(𝜀𝑝 + 𝜌𝑝𝐾𝑒𝑞)

𝑧𝐹𝜇𝑖

𝜎𝑝

𝑗
=

𝐿𝑝(𝜀𝑝 + 𝜌𝑝𝐾𝑒𝑞)

𝑧𝐹𝜇𝑖

𝐿𝑝

∆𝑉𝑝
 (5) 

With the initial condition 𝐶𝑝,𝐶𝑟(0, 𝑧) = 0 and the boundary conditions (constant in time as first approximation) 

 𝐶𝑝,𝐶𝑟(0, 𝑡) = 𝐶0,𝐶𝑟, that correspond to the solution concentrations in the anodic and cathodic compartments, 

assumed the same by the effect of the external recirculation. About diffusivities, typical values are 𝐷𝐶𝑟 =  1 ∙

10−9 𝑚2/𝑠 and 𝐷𝐻 =  1 ∙ 10−7 𝑚2/𝑠 (Sathish et al., 2019). Thus, the penetration of hydrogen is significantly faster 

than that of chromium. It is convenient to verify the negligible relevance of diffusion with respect migration by 

the comparison of the two characteristic times: 

𝜏𝐷

𝜏𝑀
=

𝐿𝑝
2 𝜏𝑝

𝜀𝑝𝐷𝑖

∆𝑉𝑝

𝐿𝑝
2 𝑧𝐹𝜇𝑖 ≈

𝜏𝑝𝑧𝐹𝜇𝑖

𝜀𝑝𝐷𝑖
∆𝑉𝑝 ≈

𝜏𝑝𝑧𝐹

𝜀𝑝𝑅𝑇
∆𝑉𝑝 ≈

96500 ∙ 10 

0.3 ∙ 8.313 ∙ 300
∆𝑉𝑝 ≈ 1300 ∆𝑉𝑝 (6) 

It clearly appears that diffusion has characteristic times 3 orders of magnitude higher than those of migration 

even with applied potentials of the order of 1 𝑉. This is precisely the reference value because, as already pointed 

out, we must avoid the electrolysis of water and the oxidation of 𝐶𝑟(𝐼𝐼𝐼) to 𝐶𝑟(𝑉𝐼). Accordingly, it is not necessary 

to differentiate the composition in the two cell compartments with a significant simplification of the cell design. 

1 V

O V

754



Under these approximations it is possible to obtain an analytical solution through the method of characteristics 

for the simplified version of eq. (3) (Polyanin, 2002): 

𝜕𝐶𝑝,𝐶𝑟

𝜕𝑡
=

1

𝜏𝑀

𝜕𝐶𝑝,𝐶𝑟

𝜕𝑧
 (7) 

that is 𝐶𝑝,𝐶𝑟 ≈ 𝐶𝐿,𝐶𝑟 at 𝑡 ≈ 𝜏𝑀, where, for the process conditions adopted here: 

𝜏𝑀 =
𝐿𝑝(𝜀𝑝 + 𝜌𝑝𝐾𝑒𝑞)

𝑧𝐹𝜇𝑖

𝐿

∆𝑉𝑝
≈

𝐿𝑝
2 (𝜀𝑝 + 𝜌𝑝𝐾𝑒𝑞)

𝑧𝐹𝐷𝑖

𝑅𝑇

∆𝑉𝑝
≈

174

∆𝑉𝑝
 𝑠 (8) 

The good fit about the migration time by eq. (8) can be seen in Figure 4(b).  

 

 (a) 

 
(b) 

Figure 4. (a) Total chromium content in tanned leather (mg/kg) as a function of time at different applied 

voltage (0 ÷  2 𝑉); (b) predictive fit of eq. (8) to experimental migration times 

5. Conclusions 

This work demonstrated the great innovation of a tanning process sustained by the application of an electric 

field. The main conclusions that can be drawn from the experimental point of view are: 

− it is confirmed the possibility to run a very fast tanning process, in the order of about 500 times lower, 

leading to a tanned leather with a chromium content even greater than that of conventional processes; 

− the process is intrinsically safe because the lower voltages and consequently no risk of 𝐻2 development 

and no oxidation to toxic 𝐶𝑟(𝑉𝐼); 

− it is confirmed the unidirectional ion penetrations from anode to cathode 

All these aspects are confirmed by the preliminary process modelling: 

− Short time process, below 2 min; 

− Asymptotic 𝐶𝑟(𝐼𝐼𝐼) in leather controlled by 𝐶𝑟(𝐼𝐼𝐼) in tanning bath; 

− Tanning time controlled by ∆𝑉/𝐿𝑝  

− Negligible influence of 𝑄𝐿   

Accordingly, these results are the basis to start the design of an industrial tanning cell where the leather is 

continuously fed to the machine and with a residence time in the order of 2 min.  

Considering the necessary specific power obtained in the laboratory 𝑃𝑊
𝑠 = 0.02 ÷ 1.20 𝑊/𝑚2, the continuous 

cell must be powered by a power between 𝑃𝑊 = 𝐵𝐿𝑒𝑙𝑃𝑊
𝑠  and 𝑃𝑊

𝑠 = 0.01 ÷ 0.6 𝑊, confirming the negligible 

electrical consumption, in the maximum order of one hundredth of a 𝑘𝑊ℎ per single skin. 

 

Nomenclature 

 

𝑏𝐶𝑟 – Cr adsorption constant in leather, [𝑚3/𝑘𝑔] Γ –  Cr adsorbed in leather, [𝑚𝑔/𝑘𝑔] 

𝐶𝑝,𝐶𝑟 –  [𝐶𝑟] in the liquid phase contained in the macropores, [𝑚𝑔/𝐿] 𝑡 –  process time for the experiment, 𝑠 

𝐶𝐿,𝐶𝑟
0  – [𝐶𝑟] in solution at time 0, [𝑚𝑔/𝐿] 𝑚𝑝 – hide weight, [𝑘𝑔] 

𝜌𝑐 – collagen apparent density, [𝑘𝑔/𝑚3] 𝜌𝑝 – hide apparent density, [𝑘𝑔/𝑚3] 

𝑄𝐿 – recirculation flow rate of tanning solution, [𝑚𝐿/𝑚𝑖𝑛]  𝐶𝑝,𝐶𝑟
𝑡𝑜𝑡  – final [𝐶𝑟] in leather, [𝑚𝑔/𝑚3] 

𝛤∞ – saturation of Cr adsorbed in leather,  [𝑚𝑔/𝑘𝑔] ∆𝑉 – standard potential,  [𝑉] 

𝑉𝐿 –  tanning solution volume, [𝐿] 𝜀𝑝 – macroporosity, [ ] 

𝐶𝐿,𝐶𝑟 –  [𝐶𝑟] in tanning solution at the end of the process, [𝑚𝑔/𝐿] 𝑉 – electric potential, [𝑉] 

𝑏𝐻 – H adsorption constant in leather, [𝑚3/𝑘𝑔] 𝑥 – cross-sectional dimension, [𝑚𝑚] 

755



𝐶𝑝,𝐻 – [𝐻] in the liquid phase contained in the macropores, [𝑚𝑜𝑙/𝐿] 𝑗 – current density, [𝐴/𝑚2] 

𝐾𝑒𝑞 – adsorption equilibrium constant, [𝑚3/𝑘𝑔] 𝜎𝑝 – leather electric conductivity, [𝑆/𝑚] 

∆𝑉𝑝 – potential difference measured on leather [𝑉] 𝐿𝑝 – leather length [𝑚𝑚] 

𝑧 – not dimensional coordinate, [0,1] 𝜏𝑀 – migration time [𝑠] 

𝜏𝑝 – tortuosity, [ ] 𝜏𝐷 – diffusion time [𝑠] 

𝐷𝑖 – diffusivity, [𝑚2/𝑠] 𝜇𝑖 – diffusion time [𝑠] 

Acknowledgments 

This project was founded by MISE Powertan project n. F/310021/01/X5 “Intensified real-time processes 
(electrotan, sonotan) with high environmental sustainability for the tanning sector”, and also within MICS 
Extended Partnership (Circular and Sustainable Made in Italy), financed by the European Union – Next 
Generation EU (NATIONAL RECOVERY AND RESILIENCE PLAN (PNRR) - MISSION 4 COMPONENT 2, 
INVESTMENT 1.3 - D.D. 1551.11-10-2022, PE00000004). 

References 

Acumen Research and Consulting, 2023, https://www.globenewswire.com/news-

release/2023/02/02/2600667/0/en/Leather-Market-Size-Growing-at-6-2-CAGR-Set-to-Reach-USD-708-7-

Billion-By-2030.html, accessed 14.12.2024. 

Auad P., Spier F., Gutterres M., 2020, Vegetable tannin composition and its association with the leather tanning 

effect. Chemical Engineering Communications, 207(5), 722-732. 

Biškauskaitė R., Valeikienė V., Valeika V., 2021, Enzymes for Leather Processing: Effect on Pickling and 

Chroming. Materials,14(6),1480. 

Carçote C., Badea E., Miu L., Della Gatta G., 2016, Study of the effect of tannins and animal species on the 

thermal stability of vegetable leather by differential scanning calorimetry. Journal of Thermal Analysis and 

Calorimetry, 124, 1255-1266. 

Covington T., 2009, Tanning Chemistry: The Science of Leather. Royal Society of Chemistry. 

Covington A.D, 1997, Modern tanning chemistry. Chemical society reviews. 

Fortune, 2023, Fortune business insight 2023-2030. https://www.fortunebusinessinsights.com/leather-goods-

market-104405, accessed 14.12.2024. 

ICDA, 2024, International Chromium Development Association. https://www.icdacr.com/applications/leather-

tanning/, accessed 14.12.2024. 

Kerr J.A., 2000, CRC Handbook of Chemistry and Physics 1999-2000: A Ready-Reference Book of Chemical 

and Physical Data, CRC Press, Boca Raton, Florida, USA, 81st edition. 

Kesarwani P., Jahan J., and Kesarwani K., 2015, A review on leather processing. International Journal of 

Applied Research, 9, 977–982. 

Král I., Schmel F., Buljan J., 2014, The future for leather, UNIDO, United Nations Industrial Development 

Organization. 

Masi M., Magagnin L., Costa P.P, Costa L., 2013, Method for the conditioning of waste arising from the 

decommissioning of nuclear plants, WO2013168118. 

Masi M., Magagnin L., Rossi F., Gibertini E., Rovere G., 2019, Chromium enhanced tanning leather, 

EP3527675. 

Muralidharan V., Ramesh Rao R., Madhan B., Palanivel S., 2021, Biochemical and Physical Changes in 

Goatskin during Bacteria Putrefaction. Journal of the American Leather Chemists Association, 116, 6. 

Panduranga Rao S., Murugesan T., Surianarayan M., Raghavan K.V., 1995, Pore model for the fibrous collagen 

matrix in animal skins. Chemical Engineering Science, 50, 5, 890-897. 

Polyanin, A.D. 2002, Handbook of Linear Partial Differential Equations for Engineers and Scientists, Boca 

Raton: Chapman & Hall/CRC Press, ISBN 1-58488-299-9. 

Rossi F., Castiglione F., Ferro M., Marchini P., Mauri E., Moioli M., Mele A., Masi M., 2015, Drug-Polymer 

Interactions in Hydrogel-based Drug-Delivery Systems: An Experimental and Theoretical Study. 

ChemPhysChem, 16(13):2818-2825. 

Sathish M., Dhathathreyan A., Raghava Rao J., 2019, Ultraefficient Tanning Process: Role of Mass Transfer 

Efficiency and Sorption Kinetics of Cr(III) in Leather Processing. ACS Sustainable Chemistry & Engineering, 

7, 4, 3875-3882. 

UNIC, Unione Nazionale Industria Conciaria, 2023, Sustainability Report 2023 

Yang T., Zeng Y., Sun Q., Lei C., Shi B., 2022, Effect of Pickling Materials on Leather Quality from a Hide 

Surface Charge Perspective. Journal of the American Leather Chemists Association, 117, 7. 

756


	CET-vol117-b.pdf
	241salmi.pdf
	Powertan: a Revolution for the Tanning Leather Sector