Study On Removal Of Chromium From Wastewater By Adsorption Of Shrimp Shell And Pine Bark

Water pollution due to the disposal of heavy metals has been an increasing worldwide concern for the last few decades. The problem of removing pollutants from water and waste water has grown with rapid industrialization. The discharge of toxic metals into watercourses is a serious pollution problem, which may affect the quality of water supply. Increasing concentrations of these metals in the water can cause a severe health hazard mainly due to their non-degradability and toxicity.The study adopted the methods of biosorption to treat wastewater containing chromium with pure natural shrimp-shells and pine bark. We study the removal efficiency of trivalent chromium ions in wastewater through static and dynamic experiments. Research results are as follows:In the test of static adsorption, the adsorption rate reached 97.35% with shrimp-shells in the following conditions:the initial concentration of Cr³⁺ is 20 mg/L; pH is 5.0; temperature is 30℃; adsorbent dose is 2.0 g/L; adsorption time is 120 min. The adsorption rate reached 80.48% when the adsorbent dose is 3.0 g/L and adsorption time is 180min with the other conditions being equal. With the increase of salt ionic concentration the removal rate of Cr³⁺ with shrimp-shells and pine bark has been reduced.The adsorption of Cr³⁺ with shrimp-shells and pine bark are endothermic reaction. Freundlich isotherm adsorption equation has better fitting effect with shrimp-shells as adsorption. Langmuir isotherm adsorption equation has better fitting effect with pine bark as adsorption.The adsorption of Cr³⁺ from shrimp shell and pine bark can be well described by the pseudo two order kinetic equation （correlation coefficient R2> 0.99）.SEM-EDS, FTIR and dispersion experiment used to characterize the shrimp shell and pine bark, which prove they are good adsorbents for Cr³⁺ in the water.Study of shrimp shell dynamic adsorption of trivalent chromium solution process, the penetration time of the trivalent chromium solution shrimp shell was obtained When the column height, flow rate, initial concentration is different. When other conditions do not change, the longer the time, the greater the adsorption capacity of the shrimp shell to the trivalent chromium solution. Shrimp shell and pine bark dynamic adsorption experimental data were fitted by Thomas model to get the dynamic adsorption rate constant, dynamic adsorption equilibrium. The dynamic adsorption experiment data of shrimp shell and pine bark were fitted by BDST model and the predicted value of penetration time was obtained.The results showed that the shrimp shell had a very good regeneration, two times, three times, and the first time, the difference was not significant between the three times and the first time.