BIDANG ILMU: KIMIA (MIPA)
LAPORAN PENELITIAN HIBAH BERSAING TAHUN ANGGARAN 2011
PEMBUATAN DAN KARAKTERISASI GEL EKSTRAKTOR UNTUK PENYISIHAN LOGAM BERAT DAN NUTRIEN SECARA SIMULTAN DENGAN SISTEM EKSTRAKSI FASE PADAT
Dr. Barlah Rumhayati, M.Si Dr. Ir. Chasan Bisri Qonita Fardiyah, S.Si., M.Si
Dibiayai oleh Direktorat Jenderal Pendidian Tinggi, Kementerian Pendidikan Nasional, melalui DIPA Universitas Brawijaya REV.1 Nomor: 0636/023-04.2.16/15/2011 R, tanggal 30 Maret 2011 dan berdasarkan surat dari DP2M Dikti Nomor: 121/D3/PL/2011 tanggal 7 Februari 2011
UNIVERSITAS BRAWIJAYA NOPEMBER 2011
RINGKASAN Meningkatnya jumlah penduduk dan aktifitas manusia menyebabkan berkurangnya ketersediaan air baku air minum yang layak untuk dikonsumsi. Untuk mengatasi hal ini pemerintah Indonesia mempunyai lembaga pengolah air baku air minum seperti PDAM yang mengolah air tanah. Disamping itu secara swadaya di masyarakat terdapat depo-depo air isi ulang yang memproses air pegunungan untuk menjadi layak dikonsumsi. Proses yang dikerjakan oleh PDAM dan depo air isi ulang dalam penyisihan logam berat dan nutrien biasanya hanya dengan menggunakan sistem filtrasi. Persen penyisihan logam berat dan nutrien melalui proses filtrasi sangat kecil karena ion logam dan ion nitrat mampu lolos dari filter yang ukuran porinya dalam skala mikro. Oleh karena itu perlu dikaji metode lain untuk penyisihan logam berat dan nutrien yang lebih efisien. Salah satu metode penyisihan yang akhir-akhir ini berkembang pesat adalah ekstraksi fase padat. Metode ini memiliki beberapa keuntungan dibandingkan dengan ekstraksi cair-cair karena tidak digunakannya pelarut organik yang biasanya karsinogenik. Dalam metode ini terdapat adsorben. Berbagai adsorben yang telah digunakan dalam metode ekstraksi fase padat perlu dikondisikan terlebih dulu sebelum digunakan untuk proses penyisihan. Oleh karena itu perlu dilakukan penelitian ttg jenis adsorben yang mudah dibuat, tidak perlu pengkondisian awal, memiliki selektifitas tinggi terhadap logam berat dan nutrient. Pada penelitian ini dibuat adsorben berupa gel hasil reaksi polimerisasi monomer akrilamid dengan crosslinker berbasis turunn agarosa. Gel akrilamid sebagai matrik bagi adsorben resin Chelex-100 dan ferrihidrit. Gel chelex digunakan untuk penyisihan logam berat, dalam hal ini adalah Pb dan Cu sementara gel ferrihidrit digunakan untuk penyisihan nutrient yaitu fosfat dan nitrat. Tipe ekstraktor yang digunakan dalam penelitian ini adalah tipe disk catridge dimana gel disk dimasukkan dalam syringe dengan volume 5 ml. Kelebihan tipe ekstraktor disk catridge dibandingkan dengan tipe catridge adalah luas permukaan kontak yang besar karena digunakannya adsorben dengan ukuran kecil, tidak terjadi channeling yang dapat mengurangi persen penyisihan, serta dimungkinkannya digunakan laju alir sampel yang cepat karena tebal disk yang digunakan kurang dari 1 mm. Hal-hal yang diamati dalam penelitian ini adalah karakter fisik gel yang meliputi warna dan faktor ekspansi, pengaruh pH dan konsentrasi analit terhadap persen penyisihan analit, persen penyisihan logam berat dan nutrient dari sampel air PDAM dan air isi ulang pada pH (untuk nutrient). optimum, dan penentuan persen elusi logam berat dan nutrient dari gel disk catridge pada berbagai variasi konsentrasi asam HNO (untuk logam) dan H SO 3
2
4
Untuk membuat gel akrilamid dibutuhkan monomer akrilamid, crosslinker, akuades. Reaksi polimerisasi pembentukan gel diinisiasi oleh ammonium persulfat dan dikatalisis oleh TEMED. Gel 0
dicetak pada suhu 42-44 C selama kurang lebih 1 jam. Setelah terbentuk dimensi gel diukur. Gel dihidrasi dalam akudes minimal selama 3 jam sampai dimensinya stabil. Chelex-100 dan ferrihidrit merupakan adsorben yang digunakan untuk berinteraksi dengan logam Pb dan Cu serta nutrient fosfat dan nitrat. Pasta ferrrihidrit yang digunakan dibuat dari reaksi presipitasi antara FeCl 0,2 M 3
dengan NaOH 1 M. Pengaruh pH dan konsentrasi analit yang dipelajari adalah Pb (1 ;5 ;10 mg Pb/l pada pH 4, 5, 6, 7, 8), Cu (0,5; 1,0; 5,0; 10,0 mg Cu/l pada pH 3, 4, 5, 6), fosfat (0,1; 0,3; 0,6; 0,9 mg 3-
-
PO /L pada pH 3, 4, 5, 6, 7), dan nitrat (5,0; 10,0; 15,0; 20,0; 25,0 dan 30,0 mg NO /L pada pH 3, 4
3
4, 5, 6, 7, dan 8). Untuk penyisihan Pb, Cu, fosfat, dan nitrat dari sampel air PDAM dan air isi ulang, pH sampel dikondisikan pada pH optimum. Variasi konsentrasi HNO untuk elusi Pb dan Cu dari gel 3
chelex adalah 1, 2, 3 M. Variasi konsentrasi H SO untuk elusi fosfat dan nitrat dari gel ferrihidrit 2
adalah 0,20; 0,25; dan 0,30 M.
4
Dari hasil penelitian diperoleh bahwa gel chelex berwarna putih berasal dari warna resin chelex. Gel chelex memiliki faktor ekspansi 3,05 setelah direndam dalam akuades selama 3 jam. Gel ferrihidrit berwarna coklat berasal dari warna pasta ferrihidrit. Gel ini memiliki faktor ekspansi 2,08. Penyisihan logam Pb dan Cu didasarkan pada kemampuan gugus iminodiasetat pada chelex membentuk senyawa komplek khelat dengan ion logam. pH analit menentukan muatan gugus asetat 2+
sebagai ligan dan spesies logam. Ion Pb tertahan sampai 82,31% pada pH 6 dan konsentrasi sampai 2+
10 mg/l. Ion Cu tertahan pada gel chelex pada pH 5 dan konsentrasi 1 mg/l. Ion fosfat dan nitrat tertahan di gel ferrihidrit dengan persen retensi sebesar masing-masing 85,32% pada konsentrasi 0,3 mg/l (pH 5) dan 88% pada konsentrasi 10 mg/l (pH 5). Dari sampel air PDAM kurang lebih 72,9% Pb, 76,5% Cu, 78,8% fosfat, dan 63,4% nitrat mampu disisihkan sementara gel chelex dan gel ferrihidrit mampu menyisihkan 77,8% Pb, 73,3%Cu, 72,99% fosfat, dan 76,5% nitrat dari air isi ulang (air depo). Ion logam teretensi dalam gel chelex dapat dielusi dengan asam nitrat. Dengan menggunakan HNO 2 M, ion Pb dapat terelusi hingga 75,1% dan 81,5% ion Cu dapat dielusi. Fosfat dan nitrat 3
dapat dielusi dari gel ferrihidrit dengan asam sulfat. Pada konsentrasi H SO 0,3 M, 81,5% fosfat 2
4
terelusi dan 77,5% nitrat terelusi. Dari hasil penelitian ini dapat disimpulkan bahwa gel disk catridge secara tunggal mampu menyisihkan logam berat Pb dan Cu serta nutrien fosfat dan nitrat. Namur gel disk catridge tunggal kurang efisien dan praktis. Oleh karena itu diusulkan untuk diteliti pembuatan gel disk catridge dengan susunan berseling gel chelex dan gel ferrihidrit untuk menyisihkan Pb, Cu, fosfat, dan nitrat secara simultan.
SUMMARY The increasing of population number and also human activities has caused the decreasing of drinking water sources which is safe consumed. To solve this problem, Indonesian has an organization, called PDAM, which has responsible for processing drinking water source. Besides that, there are many refilling units in public which has proceeded mountain water to be safe for consuming. PDAM and refilling units usually use filtration process for removal heavy metals and nutrient. However, the percentage of removal of these analytes is low because of its small particle size so easily passing through the membrane filter. Hence, it is needed to investigate another method for removing heavy metals dan nutrient. Recently, solid phase extraction becomes famous method for removal contaminants. The advantages of this method compared to liquid-liquid extraction is using no carcinogenic organic solvents. Adsorbent is used in the solid phase extraction method to interact with analytes. Many adsorbents have been used in the solid phase extraction and they need to be preconditioned before using. Therefore, the investigation of new sorbents which is easy to be prepared, no needed precondition, has high affinities to heavy metals and nutrient is important. In this research, adsorbent used was in the gel form that is produced by polymerization reaction between acrylamide monomer with agarose derivates crosslinker. Acrylamide gel is acted as a matrix for Chelex-100 resin and ferrihydrite. Chelex gel was used for heavy metals, Pb and Cu, removal whilst ferrihydrite gel was used for removal of nutrient such as phosphates and nitrate. Extractor type used in this research was disk catridge model where the gel disk is filled in the syringe 5 ml. The advantages of using disk catridge compared to conventional catridge are high surface area due to small particle size of adsorbent, reduced channeling, possible to have high flow rate of sample. Factors investigated in this research were physical properties of the gel including color and expansion factor, the effect of analyte’s pH and concentration to the removal percentage, removal of Pb, Cu, phosphate, and nitrates from PDAM water and refilling unit water at optimum pH, and the effect of acid eluent concentration to the elution percentage. Acrylamide monomer, agarose derivative crosslinker, akuades were needed to prepare acrylamide gel. Polymerization reaction was initiated by ammonium persulfate and was catalyzed by TEMED. Gels were cast at 42-44 C for at least 1 hour. After casting, the dimension of the gels was determined. Gels were hydrated for 3 hours in aquadest up to stable dimensionally. Chelex-100 resin and ferrihydrite paste were used as adsorbent for interacting with Pb and Cu metals, and for phosphate and nitrate nutrients. Ferrihydrite paste was produced by precipitation reaction between FeCl 0.2 M and NaOH 1 M. The pH and concentration of analytes were studied with variation as 3
follows: Pb (1 ;5 ;10 mg Pb/l at pH 4, 5, 6, 7, 8), Cu (0,5; 1,0; 5,0; 10,0 mg Cu/l at pH 3, 4, 5, 6), 3-
phosphate (0,1; 0,3; 0,6; 0,9 mg PO /L at pH 3, 4, 5, 6, 7), and nitrate (5,0; 10,0; 15,0; 20,0; 25,0; 4
-
30,0 mg NO /L at pH 3, 4, 5, 6, 7, dan 8). For studying of Pb, Cu, phosphate, and nitrate removal 3
from PDAM water and refilling water samples, the pH of samples were conditioned at optimum pH. For elution, it used various concentration of HNO (for eluting Pb and Cu from chelex gel) of 1, 2, 3 3
M. Concentration of H SO was varied of 0,20; 0,25; dan 0,30 M for elution of phosphate an nitrate 2
4
from ferrihydrite gel. As a result, chelex gel has white color due to white color of chelex resin. Its expansion factor was 3.05 after 3 hours hydration. The color of ferrihydrite gel was brown from the color of ferrihydrites precipitate. The gel has 2.08 expansion factor.
Removal of Pb and Cu metals are based on the formation of chelate complex compounds between iminodiacetic functional groups and metal ions. Analyte pH determines the charged of 2+
acetic functional groups and metal specieses. Pb ion was retented up to 82,31% at pH 6 and its 2+
initial concentration was up to 10 mg Pb/l. Cu ion was retented on the chelex gel at pH 5 with maximum of initial concentration was 1 mg Cu/l. Phosphate and nitrate ions were retented in the ferrihydrite gel up to 85,32 % (at initial concentration of 0,3 mg fosfat /l and pH 5), dan 88% (at initial concentration of 10 mg nitrate/l and pH 5), respectively. From water samples, 72,9% Pb, 76,5% Cu, 78,8% phosphate, and 63,4% nitrate were removed from PDAM water 77,8% Pb, 73,3%Cu, 72,99% phosphate, and 76,5% nitrate were removed from refilling water. Metals ion could be eluted from the chelex gel by using nitric acid eluent. Ion logam teretensi dalam gel chelex dapat dielusi dengan asam nitrat. 75,1% Pb and 81,5% Cu could be removed by HNO 2 M. Phosphate and nitrate could be eluted from the ferrihydrite gel by using H SO 0,3 M at 3
2
4
the elution percentage were 81,5% phosphate and 77,5% nitrate. Based on the results, it can be concluded that the individual gel disk catridge could be used for removal of heavy metals such as Pb and Cu, and also for phosphate and nitrate nutrients. However, the use of individual catridge is not practice and efficient. Hence, it can be proposed to produce gel disk catridge with filled by gel chelex and gel ferrihydrite sequentially for removal of Pb, Cu, phosphate, and nitrates simultaneously.
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