Kristalisasi Magnesium Karbonat dari Limbah Proses Pembuatan Garam Rakyat - Magnesium Carbonate Crystallization From Traditional Salt Production Wastewater

Apriani, Mirna (2018) Kristalisasi Magnesium Karbonat dari Limbah Proses Pembuatan Garam Rakyat - Magnesium Carbonate Crystallization From Traditional Salt Production Wastewater. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Tambak garam rakyat menghasilkan limbah berupa larutan garam yang tersisa di petak kristalisasi setelah panen garam. Limbah tambak garam (bittern) biasanya dibuang kembali ke laut oleh sebagian besar petani garam. Magnesium di dalam limbah ini memiliki kandungan sebesar 20-30 kali lipat daripada air laut sehingga perlu pengelolaan sebelum dibuang ke laut. Magnesium dibutuhkan untuk kesehatan manusia dan kegiatan industri. Pengolahan limbah melalui recovery magnesium dapat meningkatkan nilai ekonomi limbah dan air laut sebagai sumber mineral selain produksi garam. Penelitian recovery magnesium bertujuan untuk mengkaji karakteristik limbah tambak garam, menemukan kondisi operasi pH dan nilai Baume (Be) pada sintesa magnesium karbonat dari limbah tambak garam, menemukan koefisien laju reaksi pembentukkan inti kristal dan koefisien perpindahan massa volumetrik pertumbuhan kristal, menghasilkan korelasi empirik kristalisasi magnesium karbonat dan mendapatkan kinerja Fluidized Bed Crystallization (FBC) tanpa dan dengan resirkulasi. Sampling limbah tambak garam dilakukan berdasarkan data sekunder lokasi tambak garam di Jawa Timur. Sampling dilakukan di petak kristalisasi setelah panen garam. Metoda sintesa magnesium karbonat dari bittern dilakukan menggunakan kristalisasi reaksi antara magnesium dan sodium karbonat pada suhu ruang. Penelitian dilakukan pada kondisi operasi pH (8-10) dan konsentrasi awal magnesium sebesar 10.200-40.800 mg/L. Sintesa magnesium karbonat menggunakan pengadukan dengan gradient kecepatan 20 detik-1 selama 30 menit. Morfologi kristal diobservasi menggunakan Scanning Electron Microscopy (SEM) dan Energy dispersive X-ray Spectroscopy (EDS) yang dikonfirmasi dengan X-ray diffraction (XRD). Kinetika reaksi pembentukkan inti kristal magnesium karbonat dilakukan menggunakan limbah sintetis yang direaksikan dengan sodium karbonat pada pH 10. Pengukuran penurunan konsentrasi magnesium dilakukan melalui monitoring nilai electrical conductivity selama proses untuk mendapatkan konstanta kecepatan reaksi. Persamaan kinetika reaksi menggunakan pendekatan orde reaksi, pemilihan persamaan ditentukan dari nilai R2 paling mendekati 1. Penentuan koefisien perpindahan massa volumetrik kristalisasi dilakukan menggunakan reaktor FBC dengan limbah sintetis. Analisa dimensi menggunakan Buckingham π theorema dilakukan untuk menentukan korelasi antara variabel-variabel yang mempengaruhi perpindahan massa. Analisa bilangan tak-berdimensi dilakukan untuk mendapatkan korelasi empirik dari variabel-variabel yang mempengaruhi kristalisasi magnesium karbonat menggunakan regresi multi variate. Uji coba reaktor kontinu skala laboratorium menggunakan limbah asli dilakukan menggunakan reaktor FBC tanpa dan dengan resirkulasi. Karakteristik limbah tambak garam memiliki nilai konsentrasi magnesium sebesar 40.800-80.400 mg/L pada Be 29-34. Sintesa magnesium karbonat nesquehonite dapat dihasilkan melalui proses operasi pH 8-9 dan konsentrasi awal magnesium sebesar 10.200-20.400 mg/L (Be 22-27). Koefisien laju reaksi kristalisasi magnesium karbonat sebesar 3 x 10-7 didapatkan dari grafik linier orde 2 yang memiliki nilai R2 paling besar yaitu 0,794. Koefisien perpindahan massa volumetrik kristalisasi magnesium karbonat yang diperoleh pada variasi limbah sintesis tanpa CMC; dengan penambahan 0,01% CMC, 0,02% CMC dan 0,03% CMC adalah berturut-turut 0,00029; 0,0002; 0,00018 dan 0,00015. Korelasi empirik bilangan tak-berdimensi untuk variabel koefisien perpindahan massa volumetrik, koefisien difusi zat cair, diameter seed, laju aliran, densitas dan viskositas dalam bentuk bilangan Schimdt dan Reynold sebagai berikut: (k_L a.d_eq)/v=1,69x〖10〗^(-9).(N_Sch )^0,38.(N_Re )^0,87 FBC menggunakan pasir sebagai seed material dapat menghasilkan penurunan magnesium pada limbah tambak garam sebesar 82,7% tanpa resirkulasi dan 92,3% dengan resirkulasi. ============================================================Traditional salt production wastewater remains after salt harvesting in crystallization plot called bittern. Bittern was discharged back into the sea by the most of salt farmers. Magnesium concentration in bittern can reach 20-30 times of seawater, required its management before discharged to sea. Magnesium is needed for human health and industrial activities. Wastewater treatment through magnesium recovery can increase economic value of waste and seawater as a mineral source besides salt production. The aims of magnesium recovery research are to examine the salt production wastewater characteristics, discover operation condition (pH) and Baume (Be) in the synthesis magnesium carbonate from saltwater ponds, discover coefficient of reaction kinetics of nucleation and coefficient of volumetric mass transfer, create empirical correlation of magnesium carbonate crystallization and explore performance of Fluidized Bed Crystallization (FBC) without and with recirculation. Sampling location of salt pond wastewater was conducted based on secondary data of salt pond in East Java. Sampling was conducted in crystallization plot after salt harvest. The method of magnesium carbonate synthesis from bittern was conducted using reaction crystallization between magnesium and sodium carbonate at room temperature. The study was conducted under pH operating conditions (8-10) and initial concentrations of magnesium of 10,200-40,800 mg/L. Magnesium carbonate synthesis used stirring at velocity gradient 20 second-1 during 30 minutes. Crystalline morphology was observed using Scanning Electron Microscopy (SEM) and Energy dispersive X-ray Spectroscopy (EDS) confirmed by X-ray diffraction (XRD). Reaction kinetics of magnesium carbonate nucleation was carried out using synthetic waste reacted with sodium carbonate at pH 10. The measurement of decreased magnesium concentration was conducted by monitoring the value of electrical conductivity during process to obtain the reaction rate constant. The kinetic equation of the reaction used a reaction order approach, the selection of the equation was determined from the value of R2 closest to 1. Determination of crystallization volumetric mass transfer coefficient was conducted using FBC reactor with synthetic waste. Analysis of dimensional was carried using Buckingham π theorem. Dimensionless number analysis was done to obtain the empirical correlation of the variables that influence magnesium carbonate crystallization using multi-variate regression. The laboratory scale continues reactor tests using bittern was conducted using FBC without and with recirculation. Characteristic of salt pond wastewater has magnesium concentration 40,800-80,400 mg/L at Be 29-34. Synthesis nesquehonite magnesium carbonate produced by operating pH 8-9 and the initial concentration of magnesium is 10,200-20,400 mg/L (Be 22-27). Magnesium carbonate nucleation reaction rate coefficient of 3 x 10-7 was obtained from linear graph of order 2 which has the greatest R2 value that is 0.794. The volumetric mass transfer coefficient of magnesium carbonate crystallization obtained on the variation of synthetic wastewater without CMC; with the addition of 0.01% CMC, 0.02% CMC and 0.03% CMC respectively 0.00029; 0.0002; 0.00018 and 0.00015. An empirical correlation of the dimensionless number for variable of volumetric mass transfer coefficient, fluid diffusion coefficient, seed diameter, flow rate, density and viscosity in the form of Schmidt and Reynold number as follows: (k_L a.d_eq)/v=1,69x〖10〗^(-9).(N_Sch )^0,38.(N_Re )^0,87 Performance of FBC using sand as seed material can obtain removal percentage of magnesium in saltwater ponds by 82.7% without recirculation and 92.3% with recirculation.

Item Type: Thesis (Doctoral)
Additional Information: RSL Apr k
Uncontrolled Keywords: bittern, magnesium carbonate, mass transfer, dimensional analysis, dimensionless number, FBC
Subjects: Q Science > QD Chemistry > QD502 Chemical kinetics
T Technology > TD Environmental technology. Sanitary engineering > TD455 Chemical precipitation. Coagulation. Flocculation
Divisions: Faculty of Civil, Environmental, and Geo Engineering > Environmental Engineering > (S3) PhD Theses
Depositing User: Apriani Mirna
Date Deposited: 06 Dec 2018 02:04
Last Modified: 06 Dec 2018 02:04
URI: http://repository.its.ac.id/id/eprint/59423

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