Chromium Recovery from Tannery Wastewater
Protecting the environment and humanity from the toxicity of hexavalent chromium (Cr+6) in wastewater while recovering these non-renewable resources for reuse in the industry: a move towards circular economy.
The leather and leather products industry play a prominent role in the world’s economy, with an estimated global trade value of approximately USD 100 billion per year. Over 80% of these leather are manufactured through chromium tanning processes. In most of these tanning processes, only 60-70% of chromium is absorbed by leather, and the rest is discharged in effluents.
Kenya is ranked among the top 30 producers of leather, bovine hides and skins, sheep and lamb skins and goat skins globally. The objective of tanning process is to protect leather against decay. Most tanneries in Kenya discharge raw effluent with high content of chromium levels ranging from 10 to 300 mg/L directly into the municipal sewers and rivers in disregard of the needed effluent treatment procedures. According to the World Health Organization (WHO) drinking water guidelines, the maximum allowable limit for total chromium in drinking water is 0.05 mg l−1. Soil around tannery dump sites has been found to have chromium levels of up to 2631.38 mg/L exceeding National Environment Management Authority (NEMA)’s limit of 2 mg/L. NEMA waste management regulations limit hexavalent chromium to 0.1 mg/L of industrial effluents being discharged into water bodies.
Why treatment of tannery wastewater has not been successful
Demand for Chromium
Although chromium is toxic to human and the environment, there has not been a better replacement with other tanning compounds for the processing of hides. Chromium has excellent processing speed, low costs, light color of leather and greater stability of the resulting leather. Chromium is also used in many other industries as shown in the chart below.
The cost of Chromium salts varies depending on the type of salts; for instance, a kilogram of potassium dichromate used in tanneries is USD 2.2- USD 2.5 (Alibaba.com). Chromium metal per kilogram with 99% purity costs approximately KSh. 1,200 (USD 12). Most of the chromium used globally is mined in the following countries; South Africa, Turkey, India, Kazakhstan and Finland. Recycling of chromium can ensure its industrial application is sustainable and the environment is protected from its toxicity.
Our solution and value proposition
Our solution involves the treatment of wastewater by use of a nano-composite adsorbent material made from kaolinite and cellulose acetate polymer, which are cheap and environmentally friendly. Desorption through electrolysis process that utilizes solar energy to obtain pure chromium metal makes the solution economically feasible.
The development of the technology is inspired by the business opportunity available. The global industrial wastewater treatment market was valued at USD 10.65 billion in 2018 and is expected to reach USD 16.60 billion by the year 2026. The wastewater treatment equipment commercially available in Kenya are either inefficient or expensive to install and maintain.
Equipment Unique Value Proposition
The technology will offer a dual system that removes heavy metals such as chromium in industrial wastewater streams and allows the recovery of chromium and recycling of the treated effluent. The proposed solution is simple in design and is projected to be affordable.
SWOT Analysis Worksheet
Funding opportunities and mentorship is needed to venture into this form of entrepreneurship. The simplicity of the design and the complexity of its adsorption capability enable its application in other water sectors like domestic water treatment, borehole water desalination and defluoridation, a common problem in East Africa.
This proposal has highlighted how pure chromium may be extracted from wastewater and recycled back into the economy. The water, which is a limited resource globally, can be reused for agricultural and domestic purposes after treatment.
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Market report published by Research and Markets website
J. F. P. A. B. R. Lipin, “Chromium,” In Handbook of Chemical Economics, Inorganic, U.S. Department Of The Interior U.S. Geological Survey, Open File Report 01-381, Pp. 1-121.
W. N. M. A. J. M. M. Richard O. Oruko, “Assessment of Tannery Based Solid Wastes Management in Asili, Nairobi Kenya,” International Journal for Quality Research, Vol. 8, No. 2, P. 227–238, 2014.
M. K. A. W. A. W. D. A. S. B. Mojdeh Owlad, “Removal of Hexavalent Chromium-Contaminated Water and Wastewater: A Review,” Water Air Soil Pollution, Vols. Doi 10.1007/S11270-008-9893-7, Pp. 1-20, 2008.
J. N. O. A. A. O. Joel Mwondu, “A Survey Of Leather Waste Generation And Disposal Mode In Selected Counties In Kenya,” Journal Of Sustainability, Environment And Peace, Vol. 3, No. 1, Pp. 8-14, 2020.