Preparation of Sodium Lignosulfonate-Containing Layered Double Hydroxide and Investigation of Its Cu2+ Removal Performance

Project no. 32309 · Status: Kapanmış (Yayın bekleniyor) · 2024

Summary

<p>In&nbsp;this&nbsp;study,&nbsp;the&nbsp;removal&nbsp;of&nbsp;copper&nbsp;(Cu²⁺)&nbsp;from&nbsp;aqueous&nbsp;solutions&nbsp;was&nbsp;investigated&nbsp;using&nbsp;sodium&nbsp;lignosulfonate&nbsp;(SLS)-modified&nbsp;Mg/Fe&nbsp;layered&nbsp;double&nbsp;hydroxide&nbsp;(LDH)&nbsp;composite&nbsp;sorbents.&nbsp;Batch&nbsp;experiments&nbsp;demonstrated&nbsp;that&nbsp;the&nbsp;optimum&nbsp;conditions&nbsp;for&nbsp;Cu²⁺&nbsp;removal&nbsp;were&nbsp;0.025&nbsp;g&nbsp;sorbent&nbsp;per&nbsp;25&nbsp;mL&nbsp;solution&nbsp;and&nbsp;pH&nbsp;5.&nbsp;The&nbsp;developed&nbsp;sorbents&nbsp;exhibited&nbsp;fast&nbsp;adsorption&nbsp;kinetics,&nbsp;and&nbsp;Cu²⁺&nbsp;removal&nbsp;was&nbsp;found&nbsp;to&nbsp;conform&nbsp;to&nbsp;the&nbsp;&nbsp;pseudo-second-order&nbsp;(PSO)&nbsp;kinetic&nbsp;model.</p><p>Isotherm&nbsp;studies&nbsp;revealed&nbsp;that&nbsp;the&nbsp;system&nbsp;followed&nbsp;the&nbsp;Langmuir&nbsp;model,&nbsp;with&nbsp;maximum&nbsp;sorption&nbsp;capacities&nbsp;determined&nbsp;at&nbsp;50°C&nbsp;of&nbsp;156.27&nbsp;mg/g&nbsp;for&nbsp;LDH,&nbsp;81.74&nbsp;mg/g&nbsp;for&nbsp;LDH+3SLS,&nbsp;and&nbsp;127.19&nbsp;mg/g&nbsp;for&nbsp;LDH+6SLS.&nbsp;Thermodynamic&nbsp;analysis&nbsp;showed&nbsp;that&nbsp;the&nbsp;Cu²⁺&nbsp;removal&nbsp;process&nbsp;was&nbsp;endothermic&nbsp;and&nbsp;spontaneous&nbsp;for&nbsp;all&nbsp;sorbents&nbsp;(ΔH°:&nbsp;34.3-91.6&nbsp;kJ/mol).&nbsp;In&nbsp;regeneration&nbsp;studies,&nbsp;complete&nbsp;recovery&nbsp;(100%)&nbsp;of&nbsp;Cu²⁺&nbsp;was&nbsp;achieved&nbsp;for&nbsp;pristine&nbsp;LDH&nbsp;using&nbsp;10%&nbsp;diethanolamine&nbsp;solution,&nbsp;whereas&nbsp;the&nbsp;recovery&nbsp;efficiency&nbsp;for&nbsp;SLS-containing&nbsp;sorbents&nbsp;ranged&nbsp;between&nbsp;29%&nbsp;and&nbsp;76%.</p><p>Selectivity&nbsp;studies&nbsp;revealed&nbsp;that&nbsp;competing&nbsp;ions&nbsp;such&nbsp;as&nbsp;Na⁺,&nbsp;K⁺,&nbsp;Ca²⁺,&nbsp;and&nbsp;Mg²⁺&nbsp;did&nbsp;not&nbsp;significantly&nbsp;affect&nbsp;Cu²⁺&nbsp;removal&nbsp;efficiency&nbsp;at&nbsp;low&nbsp;concentrations,&nbsp;but&nbsp;a&nbsp;moderate&nbsp;reduction&nbsp;in&nbsp;performance&nbsp;was&nbsp;observed&nbsp;at&nbsp;high&nbsp;concentrations,&nbsp;particularly&nbsp;for&nbsp;the&nbsp;SLS-containing&nbsp;sorbents.&nbsp;Mechanistic&nbsp;studies&nbsp;supported&nbsp;by&nbsp;FTIR,&nbsp;XRD,&nbsp;SEM,&nbsp;and&nbsp;XPS&nbsp;analyses&nbsp;showed&nbsp;that&nbsp;as&nbsp;the&nbsp;SLS&nbsp;content&nbsp;increased,&nbsp;the&nbsp;Cu²⁺&nbsp;removal&nbsp;mechanism&nbsp;shifted&nbsp;from&nbsp;Mg-&nbsp;and&nbsp;Fe-centered&nbsp;surface&nbsp;complexation&nbsp;within&nbsp;the&nbsp;LDH&nbsp;lattice&nbsp;toward&nbsp;electrostatic&nbsp;interaction&nbsp;with&nbsp;the&nbsp;sulfonate&nbsp;groups&nbsp;of&nbsp;SLS.&nbsp;This&nbsp;study&nbsp;demonstrates&nbsp;that&nbsp;SLS/LDH&nbsp;composite&nbsp;sorbents&nbsp;prepared&nbsp;via&nbsp;co-precipitation&nbsp;are&nbsp;an&nbsp;effective&nbsp;alternative&nbsp;for&nbsp;Cu²⁺&nbsp;removal&nbsp;from&nbsp;aqueous&nbsp;solutions.</p><p><strong>Keywords:</strong>&nbsp;Layered&nbsp;double&nbsp;hydroxide,&nbsp;copper&nbsp;removal,&nbsp;sodium&nbsp;lignosulfonate,&nbsp;water&nbsp;treatment,&nbsp;heavy&nbsp;metal&nbsp;removal</p>

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