The　removal　of　copper　from　solution　by　oyster　shell　powder　was　investigated　for　potential　wastewater　treatment　uses.　In　particular,　adsorption　behavior　differences　between　the　prismatic　(PP)　and　nacreous　(NP)　shell　layers,　and　how　this　affects　copper　removal,　were　investigated.　Experimental　results　indicated　that　copper　adsorption　was　highly　pH-dependent　with　optimal　copper　removal　at　pH　5.5,　where　the　powdered　whole　raw　shell　(RP)　removed　up　to　99.9%　of　the　copper　within　24h　at　a　10　mg/L　initial　copper　concentration.　Langmuir　and　Freundlich　models　were　used　to　analyze　the　isotherm　PP,　NP　and　RP　data.　These　results　showed　a　strong　homogeneous　Langmuir　model　for　low　initial　copper　concentrations　(5-30　mg/L)　to　both　RP　and　PP　layer,　while　strong　agreement　with　a　heterogeneous　Freundlich　model　for　high　initial　copper　concentrations　(30-200　mg/L);　nevertheless,　a　homogeneous　Langmuir　model　provided　the　best　fit　for　the　more　dense　NP　layer　across　the　initial　concentration　range　(5-200　mg/L).　The　distribution　coefficient　WO　value　of　PP　layer　for　each　initial　concentration　investigated　was　substantially　higher　than　the　NP　layer　and　it　was　also　found　that　the　PP　layer　dominated　the　adsorption　process　with　an　adsorption　capacity　of　8.9　mg/g,　while　the　adsorption　capacity　of　the　NP　layer　was　2.6　mg/g.　These　differences　are　believed　to　be　because　of　the　more　porous　structure　of　the　PP　layer,　which　was　confirmed　by　scanning　electron　microscopy,　infrared　spectroscopy,　energy-dispersive　X-ray　spectroscopy,　and　thermogravimetry　differential　thermal　analyses.　(C)　2014　Elsevier　B.V.　All　rights　reserved.