Development Of Modified Biopolymer Adsorbents From Natural Polysaccharides For Renewal Of Abattoir Wastewater

Abstract

The wastewater effluents produced by poultry and the red meat industries were analysed in the quest to detect the presence of heavy metals in abattoir wastewater and to establish and optimize alternative methods of purifying wastewater from Bloemfontein abattoirs in an effort to reduce water pollution. Water samples were randomly collected from two categories of local abattoirs in Bloemfontein, namely poultry and red meat abattoirs. The samples were found to contain high levels of alkali and alkaline earth metals (Ca, Mg, K and Na) at rates above 100 mg/ℓ. Other elements present in the wastewater samples that were analyzed included Cr, Ni, Cu and Pb, which are elements that have been reported to cause devastating effects in animals and the environment. Analyses of the Cr, Ni, Cu and Pb using ICP-OES showed the presence of ultra-trace levels (0.05 – 0.2 mg/ℓ) in both wastewater solutions. These elements confirmed the presence of heavy metals in the water bodies at the abattoirs. A chromatographic technique using different chitosan products as adsorbents was developed. Some cross-linked chitosan products were synthesized from different chitin (mussel, prawn, pang and silver) products. The modified chitosan products were obtained from cross-linking the chitin with glutaraldehyde, formaldehyde, epichlorohydrine, maleic anhydride, p-benzoquinone, poly (ethylene) glycol diglycidyl ether (PEG diglycidyl ether), 1-vinyl-2-pyrrolidone, 1,3-dichloroaceone, acrylic acid and s-methyl-benzylamine. Characterization of these cross-linked chitosan products was performed using FTIR, SEM and viscometer assessments. The results obtained from the analyses using SEM spectroscopy revealed that the different products had different morphological structures. The results of the analyses showed significant adsorption rates of alkali and alkaline earth metals (Ca, Mg, K and Na) using shrimp chitosan that was cross-linked with maleic anhydride (J1) and shrimp chitosan that was cross-linked with acrylic acid (I2) chitosan products. The shrimp and crab chitosan starch that was cross-linked with formaldehyde (C1 and C2) was also shown to effectively adsorb the alkali and alkaline earth metals present in the waste samples. Lower concentrations of heavy metals were recovered (0.05 - 0.2 mg/ℓ) for Cr, Ni, Cu and Pb using these chitosan products. Although no complete adsorption of these elements was achieved in both the wastewater samples, the results showed a substantial improvement of the water eluted which demonstrated the effectiveness of the method using synthesized chitosan products.