Decontamination of tannery industry wastewater containing high organic load along with Cr³⁺: a comparative study

Abstract

The applicability of different advance oxidation processes (UV, H 2 O 2 /UV, Fe 2+ /H 2 O 2 /UV and Fe 3+ /H 2 O 2 /UV, Fe 2+ /H 2 O 2 ) to treat real tannery wastewater was investigated in this work, and their efficiency was compared. Reduction of chemical oxygen demand (COD) and removal of chromium was envisaged through two consecutive processes: COD reduction followed by chromium removal. Comparisons of the specific energy consumption between UV, UV/H 2 O 2 system, UV/H 2 O 2 /Fe 2+ , UV/H 2 O 2 /Fe 3+ system were also reported. The chemical precipitation processes with different precipitating agents, CaO, MgO and NaOH, for the removal of chromium was investigated. Chromium removal and sludge volume at different pH values for three precipitating agents were assessed. The sludge generated during chemical precipitation has been characterized. The experimental results show that optimum conditions for Fe 2+ /H 2 O 2 are 2 M H 2 O 2 , 0.04 M Fe 2+ , pH 3 and for Fe 2+ /H 2 O 2 /UV these are 0.5 M H 2 O 2 , 0.04 M Fe 2+ . The photo-Fenton system with lower H 2 O 2 dosage (0.5 M) and lower duration (60 min) could achieve same extent of COD reduction (97%) achieved in Fenton's treatment with higher (2 M) H 2 O 2 dosage and longer duration (90 min) of treatment.The results demonstrated that the photo-Fenton process was superior over other processes. The wastewater treated with CaO and MgO met the stringent discharge limit of below 1 mg/L for total chromium.

Synthesis of zeolite A using raw kaolin from Ethiopia and its application in removal of Cr(III) from tannery wastewater

“…The tanning process is commonly carried out using Cr(III), and later on, the secondary treatment may generate Cr(VI) that has adverse effects on human health. Several methods have been used for removal of chromium from tannery wastewater: biological methods, membrane technologies, chemical precipitation, ion exchange, and adsorption . These adsorbents and ion exchangers include activated carbon, fly ash, peat, recycled alum sludge, peanut hulls, resins, biomaterials, clay materials and zeolites .…”

“…Several methods have been used for removal of chromium from tannery wastewater: biological methods, membrane technologies, chemical precipitation, ion exchange, and adsorption. 5,6 These adsorbents and ion exchangers include activated carbon, fly ash, peat, recycled alum sludge, peanut hulls, resins, biomaterials, clay materials and zeolites. [7][8][9][10][11] Along with the known ion exchangers, zeolites are worthy of special attention due to their high exchange capacity, reasonable costs and environmental compatibility.…”

Synthesizing of Zeolite Particle Using Alkaline Plant Extract

“…The operational cost of these technologies is still considered expensive and sometimes involve complex steps and process. The adsorption separation as reported by [11] is the most popular and invariably the cheaper and simple alternative methods.…”

Zeolite Integrate with Natural Absorbance to Increase Crop Production

“…Zeolite enhances the cation exchange capacity of soil and increases water retention in the root zone [2][3][4]. Additionally, the higher absorption of its capability able to reduce the leaching of mineral components with at the same time capture a significant amount of heavy metals and organic pollutants in the polluted soils [4][5]. The use of zeolite, which is not acidic but rather slightly alkaline, in conjunction with fertilisers can help to buffer soil pH levels, thereby reducing the need for lime application.…”