PENGARUH WAKTU KRISTALISASI DAN TEMPERATUR PEMERAMAN TERHADAP KARAKTER ANALCIM YANG DISINTESIS DARI LUMPUR LAPINDO DENGAN TEKNIK FUSI DAN HIDROTERMAL

HURUL AINI AS SILMI, Prof. Wega Trisunaryanti, M.S

2014 | Skripsi | KIMIA

Telah dilakukan sintesis analcim dari lumpur Lapindo dengan variasi penambahan sumber silika dan kondisi sintesis. Kondisi reaksi sintesis meliputi temperatur pemeraman, waktu kristalisasi dan penambahan sumber silika. Sumber silika yang digunakan berasal dari natrium silikat sintetik (kandungan SiO 2 26,5% (b/b)) dan berasal dari ekstraksi dari lumpur Lapindo. Ekstraksi sumber silika dilakukan dengan cara refluks lumpur Lapindo menggunakan NaOH 6 M selama 6 jam dan filtratnya dianalisis dengan fluoresensi sinar-X (XRF). Sintesis analcim terdiri dari dua tahap yaitu tahap perlakuan awal dan tahap sintesis. Tahap perlakuan awal terdiri dari refluks lumpur Lapindo menggunakan HCl 6 M pada variasi waktu 1 dan 6 jam. Lumpur Lapindo hasil refluks asam kemudian dilebur dengan NaOH pada rasio molar NaOH/lumpur 1,2. Tahapan sintesis dilakukan dengan mereaksikan bahan baku hasil peleburan dengan air di dalam kondisi hidrotermal tanpa penambahan templat organik dengan komposisi awal reaktan adalah 3,6 Na2 O: Al2O3 : 5,7 SiO2 . Penambahan berbagai jenis sumber silika selama reaksi hidrotermal dilakukan untuk mempelajari pengaruhnya terhadap karakter analcim yang dihasilkan. Produk analcim dikarakterisasi dengan metode spektroskopi inframerah (IR), difraksi sinar-X (XRD) dan XRF. Analcim dengan kristalinitas tertinggi dianalisis morfologi dan komposisi kimianya dengan scaning elektron mikroskopi dan spektrometer-dispersi energi sinar-X (SEM-EDS). Hasil penelitian menunjukkan bahwa perlakuan asam meningkatkan rasio Si/Al analcim dari 2,96 menjadi 5,02 dan 6,37 setelah perlakuan asam selama 1 dan 6 jam. Kandungan pengotor logam juga berkurang akibat perlakuan asam. Sumber silika yang diekstraksi dari lumpur Lapindo memiliki kandungan SiO2 sebesar 44% (b/b). Analcim dengan rasio Si/Al tertinggi berhasil disintesis pada kondisi temperatur pemeraman 50 o C (Sa-50) dan waktu kristalisasi 24 jam (Tk- 24). Penambahan sumber silika selama proses hidrotermal meningkatkan kristalinitas dan memperbaiki kenampakan morfologi produk analcim, namun menurunkan rasio Si/Al. Partikel analcim bervariasi pada ukuran 4,3–6,5 µm dan memiliki morfologi partikel berbentuk trapezohedral.

The effect of variations in silica sources and reaction conditions on the characteristics of synthesized analcime has been studied. Variations in reaction condition in the scope of this study were aging time, and cristalisation time, while the silica sources used were sodium silicate synthetic (SiO 2 26.5% (w/w)) and sodium silicates extracted from Lapindo mud. Silicates from Lapindo mud were extracted via reflux with 6 M NaOH for 6 h and the filtrate were analysed using X-ray Fluorescence (XRF). The synthesis steps of analcime were divided into two steps, the pre-treatment step and the synthesis step. The pre-treatment step consists of treating Lapindo mud with 6 M HCl under 1 and 6 h, treated Lapindo mud was then labeled as analcime precursor and was then fused with NaOH at molar ratio of NaOH/mud of 1.2. The synthesis steps were carried out as follows: fused precursor was reacted with water under hydrothermal condition without using any organic templates with initial molar ratio of 3.6 Na2O : Al2O3 : 5.7 SiO2 . In addition, silicates from various source was added into the system prior the hydrothermal reaction to study the effects on the properties of synthesized analcime. Analcime was then characterized by infrared (IR) spectroscopy, X-ray Diffraction (XRD), and XRF. Analcime with the highest crystallinity was then analysed for its morphology and chemical composition with scanning electron microscope-energy dispersive X-ray (SEM-EDS) apparatus. The results showed that acid-treatment increased the Si/Al ratio of analcime from 2.96 to 5.02 and 6.37 after acid treatment for 1 and 6 h respectively. Metal impurities were also found to be decreased by acid treatment of Lapindo mud. Silicate extracted from Lapindo mud had a SiO 2 content of 44% (w/w). Analcime with the highest Si/Al ratio was obtained under aging temperature at 50 o C (Sa-50) and crystallisation time at 24 hour (Tk-24). Silicate addition during hydrothermal process increased the crystallinity and improved the morphology of analcime product, but decreased its Si/Al ratio. Analcime particle size varied from 4.3-6.5 µm and has a trapezohedron morphology.

Kata Kunci : Lumpur Lapindo, Natrium silikat, Fusi, Hidrotermal, Analcim trapezohedral