SINTESIS KARBOKSIMETIL KITOSAN DAN APLIKASINYA SEBAGAI ADSORBEN Pb(II)

DEWI KURNIATI S.Si, Dr. Dwi SIswanta, M.Eng.

2011 | Tesis | S2 Ilmu Kimia

Telah dilakukan penelitian tentang sintesis karboksimetil kitosan dan aplikasinya sebagai adsorben Pb(II). Sintesis karboksimetil kitosan dilakukan dengan mereaksikan kitosan dan asam kloroasetat selama 12 jam pada suhu 78 o C. Karboksimetil kitosan yang terbentuk ditentukan kandungan gugus –COOH nya dengan menggunakan metode titrasi potensiometri. Padatan hasil sintesis juga dikarakterisasi dengan spektrofotometer infra merah dan Gas Sorption Analyzer (GSA). Adsorpsi logam Pb(II) dilakukan dengan metode batch adsorption sebagai fungsi pH, waktu kontak, dan konsentrasi ion Pb 2+ . Kajian adsorpsi Pb(II) dilakukan pada konsentrasi awal 100 mg/L dan pH larutan divariasikan dari 2-7. Jumlah ion Pb(II) yang teradsorpsi ditentukan berdasarkan konsentrasi ion logam sebelum dan sesudah adsorpsi menggunakan metode spektroskopi serapan atom. Hasil penelitian menunjukkan bahwa hasil karakterisasi karboksimetil kitosan dengan FTIR memunculkan puncak baru C=O dari gugus –COOH pada pita serapan 1743 cm -1 yang tidak terdapat pada kitosan. Pengukuran adsorpsi gas N2 diperoleh luas permukaan kitosan dan karboksimetil kitosan sebesar 0,524 m 2 /cm dan 1,125 m 2 /cm dan total volume pori kitosan dan karboksimetil kitosan masing–masing sebesar 2,073x10 -3 cm 3 /g dan 2,579 x10 -3 cm 3 /g. Kandungan – COOH pada karboksimetil kitosan sebesar 51,53 cmol/kg. Kondisi optimum adsorpsi Pb(II) pada kitosan dan karboksimetil kitosan terjadi pada pH–4 dengan konstanta laju adsorpsi sebesar 0,146 g mmol -1 min -1 pada kitosan dan 0,114 g mmol -1 min -1 pada karboksimetil kitosan yang mengikuti persamaan kinetika adsorpsi orde pseudo–2. Kapasitas adsorpsi kitosan dan karboksimetil kitosan masing-masing adalah sebesar 0,125 mmol/g dan 0,289 mmol/g. Studi selektifitas adsorpsi menunjukkan bahwa penyerapan ion Pb(II) dan ion Ni(II) pada rasio mol Pb(II):Ni(II) 1:1 karboksimetil kitosan mengadsorpsi 2 kali lebih besar daripada kitosan.

The synthesis of carboxymethyl chitosan and its application as adsorbent of Pb(II) has been studied. Synthesis of carboxymethyl chitosan was performed by reacting chitosan and chloroacetic acid at 78 °C for 12 hours. The –COOH content of carboxymethyl chitosan was determined using potentiometric titration method. The product of carboxymethyl chitosan was characterized by infrared spectrophotometry and Gas Sorption Analyzer (GSA). Adsorption process of Pb(II) was conducted in batch system and measured as a function of pH, contact time, and initial concentration of Pb(II). The adsorption of Pb(II) was examined using initial concentration of 100 mg/L and pH was varied from 2-7. Total ion Pb(II) adsorbed was determined by calculating the difference of metal ion concentration in the medium before and after adsorption using atomic absorption spectrometry method. FT-IR spectra showed that carboxymethyl chitosan exhibited a new C=O absorption peak of –COOH group at 1743 cm -1 . Surface areas of chitosan and carboxymethyl chitosan measured by N2 adsorption were 0.524 and 1.125 m 2 /g, the total pore volume of chitosan and carboxymethyl chitosan were 2.073 x10 -3 and 2.579 x10 -3 cm 3 /g, respectively. The content of –COOH in the synthesized carboxymethyl chitosan was 51.53 cmol/kg. The optimum pH in the adsorption of Pb(II) on chitosan and on carboxymethyl chitosan was observed at 4. Adsorption kinetic for both adsorbents was observed to follow pseudo second order with rate constants of 0.146 g mmol min -1 and 0.114 g mmol min -1 , respectively. Adsorption capacities of Pb(II) on chitosan and carboxymethyl chitosan were 0.125 and 0.289 mmol/g, respectively. Apparently the coexistence of Ni(II) affected the Pb(II) adsorption capacity on chitosan and carboxymethyl chitosan adsorbents, and the strongest effect was observed in concentration ratio of Pb(II):Ni(II) of 1:1 (mol/mol) and 2:1(mol/mol), respectively.

Kata Kunci : kitosan, asam kloroasetat, karboksimetil kitosan, larutan Pb(II)