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Nano zero valent iron (NZVI) is an emerging adsorbent for heavy metal removal with its high reactivity and reduction potential. However, NZVI tends to aggregate to bigger particles, thus surface area and reactivity could be decreased in applications. In this study, NZVI is synthesized while attached...

Nano zero valent iron (NZVI) is an emerging adsorbent for heavy metal removal with its high reactivity and reduction potential. However, NZVI tends to aggregate to bigger particles, thus surface area and reactivity could be decreased in applications. In this study, NZVI is synthesized while attached on coffee ground to prevent agglomeration. Then batch adsorption tests for $Pb^{2+}$ and $Cd^{2+}$ in wastewater were studied. Adsorption isotherm under pH 6 and $20^{\circ}C$ revealed that maximum adsorption capacity from the Langmuir model was 814.95 mg/g and 196.06 mg/g for $Pb^{2+}$ and $Cd^{2+}$ respectively. Based on mechanism of removing $Pb^{2+}$ involves reduction, adsorption isotherm did not fit well in experiments data. Time to reach equilibrium was 1 hour and 8 hours for $Pb^{2+}$ and $Cd^{2+}$, respectively. Pseudo 2nd order kinetic model explain well kinetics of heavy metal adsorption, thus adsorption is likely to be chemi-sorption. According to the mass transfer mechanism study, 80% of $Pb^{2+}$ and 60% of $Cd^{2+}$ were transported rapidly by surface diffusion and residuals are transported by interparticle diffusion. High adsorption capactiy for $Pb^{2+}$ and $Cd^{2+}$ would be related with suppression of aggregation, hence NZVI-coffee ground showed the outstanding potential on industrial wastewater treatment facilities with high concentration of heavy metals.

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