Synthesis of a high characteristics activated carbon from walnut shell for the removal of Cr (VI) and Fe (II) from aqueous solution: single and binary solutes adsorption

Abstract

<span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>A high performance activated carbon was synthesized using walnut shell as a</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>solid waste through a two-step zinc chloride chemical activation-thermal</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>pyrolysis process. Characterization results demonstrated its porous structure</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>with very good textural properties such as high BET surface area (1223 m</em><span style="font-size: 6pt; color: #000000; font-style: normal; font-variant: normal;"><em>2</em><span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>/g)</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>and high total pore volume (0.85 cm</em><span style="font-size: 6pt; color: #000000; font-style: normal; font-variant: normal;"><em>3</em><span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>/g). The final adsorbent was used for</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>adsorption of Fe (II) and Cr (VI) from aqueous solution. Effect ofpH, initial</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>concentration of metal ions, temperature, and contact time on adsorption</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>capacity of the adsorbent was investigated. Adsorption results revealed that</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>the maximum removal of Fe (II) and Cr (VI) ions, occurred at pH 4. 5 and 2</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>respectively, were 96.2% and 99% at 313K. The equilibrium and kinetics</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>data for adsorption of single-component ions were well described by the Sips</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>isotherm and the pseudo-nth-order models, respectively. The impact of</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>competing ions was studied by adsorption of a binary solution of Fe (II) and</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>Cr (VI) ions. The binary adsorption isotherm was described by the modified</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>Langmuir model and model parameters were found following an optimization</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>procedure by genetic algorithm. Finally, the developed walnut-shell based</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>activated carbon showed higher adsorption efficiency compared to other</em> <span style="font-size: 11pt; color: #000000; font-style: normal; font-variant: normal;"><em>activated carbons at similar conditions.</em></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /><br class="Apple-interchange-newline" /></span></span></span></span></span>