Pembuatan dan Karakterisasi Membran Biodegradable Berbasis Kitosan, Asam Sitrat dan Kalsium Menggunakan Metode Sandwich Sebagai Bahan Pelapis Pupuk Lepas Lambat Urea

Anisa Nur Fitrianingrum, Taufik Abdillah Natsir, S.Si., M.Sc., Ph.D.; Prof. Dr. Endang Tri Wahyuni, M.S.

2025 | Tesis | S2 Ilmu Kimia

Penelitian ini bertujuan untuk mempelajari karakteristik membran berbasis kitosan secara berlapis dengan penambahan asam sitrat dan kalsium dan aplikasinya untuk memperlambat pelepasan urea. Penelitian dilakukan melalui tiga tahapan, yaitu: pembuatan membran, karakterisasi membran dan uji aplikasi membran sebagai bahan pelapis pupuk lepas lambat urea.

Penelitian dilakukan dengan mencampurkan kitosan (CS) dan asam sitrat (St) agar terbentuk ikatan silang untuk memperoleh campuran CS/St. Campuran CS/St selanjutnya ditambahkan nutrien urea (Ur) dan dicetak secara berlapis dengan pelapisan kalsium (Ca) untuk membentuk membran CS/St-Ur/Ca. Membran yang diperoleh ditentukan karakteristiknya berupa ketebalan, massa, derajat swelling, sudut kontak dan kuat tarik. Selain itu, membran juga dikarakterisasi menggunakan Fourier Transform Infra-Red (FTIR), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) dan Differential Scanning Calorimetry (DSC). Aplikasi membran sebagai pelapis pupuk lepas lambat urea dievaluasi dengan uji pelepasan nutrien dalam air, uji tanaman dan uji degradasi dalam tanah. 

Hasil penelitian menunjukkan bahwa modifikasi membran kitosan dengan penambahan asam sitrat dan pelapisan kalsium dapat meningkatkan ketahanan terhadap air dan kuat tarik membran. Membran CS/St-Ur/Ca4 memiliki ketahanan terhadap air yang paling baik dengan nilai derajat swelling sebesar 107,5%. Sedangkan, membran CS/St-Ur/Ca1 memiliki kuat tarik tertinggi sebesar 68,0 N/mm2. Pembuatan membran secara berlapis dengan pelapisan kalsium juga berpengaruh dalam memperlambat pelepasan urea. Membran CS/St-Ur/Ca4 memiliki pelepasan urea paling lambat dengan nilai rata-rata pelepasan N sebesar 0,31%. Selanjutnya, penambahan asam sitrat dan pelapisan kalsium menyebabkan penurunan degradasi membran dalam tanah. Berdasarkan uji degradasi, membran CS/St-Ur/Ca1 memiliki persen degradasi paling rendah sebesar 21,5%.

This study aims to investigate the characteristics of the chitosan-based multilayer membrane with the addition of citric acid and calcium and its application to slow down the release of urea. The study consists of three steps, namely: membrane preparation, membrane characterization and membrane application as a coating material for urea slow-release fertilizer.

This study was conducted by blending the chitosan (CS) and citric acid (St) to form cross-links so that CS/St mixture can be obtained. The CS/St mixture was then added with urea (Ur) then fabricated into multilayer membrane with calcium (Ca) coating to form CS/St-Ur/Ca membrane. The characteristics of the membrane were determined by measurement of thickness, mass, swelling degree, water contact angle and tensile strength. Moreover, the membrane was also characterized using Fourier Transform Infra-Red (FTIR), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) and Differential Scanning Calorimetry (DSC). Application of the membranes as a coating for urea slow-release fertilizer was evaluated through nutrient release test in water, plant test and degradation test in soil.

The results showed that modification of the chitosan membrane with the addition of citric acid and calcium coating increased the membrane's water resistance and tensile strength. The CS/St-Ur/Ca4 membrane had the best water resistance with a swelling degree of 107.5%. Meanwhile, the CS/St-Ur/Ca1 membrane had the highest tensile strength of 68.0 N/mm2. Multilayer fabrication with calcium coating also had an effect on slow down the release of urea. The CS/St-Ur/Ca4 membrane had the slowest urea release with an average N release of 0.31%. Furthermore, the addition of citric acid and calcium coating decrease membrane degradation in the soil. Based on the degradation test, the CS/St-Ur/Ca1 membrane had the lowest degradation percentage of 21.5%.

Kata Kunci : asam sitrat, kalsium, kitosan, membran, urea