Abstract
Due to the high cost associated with the treatment of effluents containing heavy metals in the environment, the continuous untreated release of effluent containing chromium from textile industries has resulted in several adverse effects to plants, ecological systems and humans. This research therefore focused on the use of a low cost, biodegradable Heinsia crinita seed coat (HCSC) material for the biosorption of chromium(VI) from aqueous and textile contaminated effluent. The biosorbent was characterized for specific surface area, surface morphology, pH point of zero charge and surface functional groups. Operational variables influences such as biosorbent dose, pH, temperature, initial Cr(VI) ion concentration and contact time on biosorption process was tested. The optimum biosorption parameter was obtained at pH 2.0, adsorbent dosage 0.25 g and contact time of 30 min. From sorption analysis, the pseudo-second-order model best described the attenuation kinetics. Concerning biosorption equilibrium, the results suggested that the adsorption isotherm obeyed the Freundlich model. Langmuir maximum monolayer biosorption capacity of 231.7 mg/g was higher than most biosorbents for Cr(VI) ion. The thermodynamic data showed a physical, spontaneous and endothermic biosorption process. HCSC showed high percentage desorption > 90% using 0.1 M HNO3 and was efficient after three cycles of regeneration studies. The results showed HCSC biomass as a suitable candidate for abstraction of Cr(VI) ion from contaminated solution and textile effluent.
Highlights
One of the major hazards in the twenty-first century is environmental pollution, due to man’s desire for improved yield in agriculture, technology and socioeconomic development with the use of chemicals
The low moisture content helps in the preparation of the Heinsia crinita seed coat (HCSC), since they require less drying before use
The high carbon content of HCSC powder showed the potentials of HCSC as a good candidate for sequestering heavy metal ions from polluted wastewater
Summary
One of the major hazards in the twenty-first century is environmental pollution, due to man’s desire for improved yield in agriculture, technology and socioeconomic development with the use of chemicals. Chromium(III) exists in nature and is needed by the body to utilize fat, protein and sugar. Cr(VI) barely exists in nature, but is normally discharged into the environment through human activities. It has been investigated and validated by the International Agency for Research on Cancer (IARC) that chromium(VI) is a potent carcinogen to humans. Consequent upon these, it is necessary and expedient to inhibit these metallic contaminants from polluting surface and ground water by condensation, dispersion, sedimentation, precipitation or dissolution and to eliminate or lower their presence in order to reduce the likelihood of animal, plant and human uptake and eventual accumulation in the food chain (Mclaughlin et al 2000; Kabata-Pendias 2001)
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