Abstract
Options to develop tanning industries could be hindered even in the presence of huge leather industry raw materials due to the requirements of high-tech contaminant removal technologies, especially in developing countries. This study was initiated to investigate the efficiency of freeze desalination for Cr(VI) removal using freezers to generate fresh water. Simulated water as well as deionized water to which known concentrations of Cr(VI) spiked into it were studied. The effects of parameters such as initial concentration, freeze duration, ice nucleation, ice volume, and influence of co-occurring ions were evaluated in relation to meltwater. The physicochemical characteristics of the produced meltwater were also evaluated. A high total water recovery of up to 85% V/V of initial water was achieved for the freeze separation rate of 90% in the experimental evaluation. Cr(VI) removal efficiency of up to 80% from simulated tap and 93 to 97% for deionized water spiked with Cr(VI) were found in this batch partial freezing. Freeze desalination was found to be relatively viable desalination technology in terms of quality of water produced, options on the use of cost effective refrigerants and technologies which could have a pertinent importance to save energy consumption of freezers.
Highlights
IntroductionChromium is one the priority pollutants list under clean water act of United States
Chromium is one the priority pollutants list under clean water act of United StatesEnvironmental Protection Agency (US EPA) which can be released into natural waters due to the discharge of a variety of industrial wastewaters
Wastewater generated by leather tanning, electroplating, textile, metal finishing industries, and wood preservatives are among the major contributing sources
Summary
Chromium is one the priority pollutants list under clean water act of United States. Environmental Protection Agency (US EPA) which can be released into natural waters due to the discharge of a variety of industrial wastewaters. Wastewater generated by leather tanning, electroplating, textile, metal finishing industries, and wood preservatives are among the major contributing sources. Uncontrolled solid and liquid waste discharges into open water systems from domestic use and industries with minimal or no treatment are common in developing countries [1]. More than 90% of the leather industries used chrome tanning. Of the Cr used in the tanning process leached into the environment [2]. Various water sources in developing countries are highly polluted with Cr(VI) [3]. In the water bodies of Ethiopian rift valley, for instance, in Koka, Ziway, and Awassa lakes and their major inflows, rivers and their inflows, and in effluents were shown to occur up to 0.269 mg/L [4,5,6] which is a value exceeding 0.05 mg/L, the maximum permissible level for drinking water set by the World Health Organization (WHO 2011)
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