Pengaruh Penambahan Fly Ash, Humat, dan Mayor Hara terhadap Sifat Fisikokimia pada Hidrogel Berbasis Selulosa

Reni Titis Wijayanti, Prof. Himawan Tri Bayu Murti Petrus, ST., M.E., D.Eng.; Prof. Ir. Panut Mulyono, M.Eng., D.Eng., IPU., ASEAN.Eng.

2025 | Tesis | S2 Teknik Kimia

Penelitian ini mengembangkan hidrogel berbahan dasar selulosa (CMC-Na dan HEC) sebagai polimer alami dan polimer sintetis (akrilamida, asam akrilat), dengan tambahan silika dari fly ash PLTU Paiton, K-humat, dan pupuk NPK untuk aplikasi pertanian berkelanjutan. Sintesis dilakukan melalui reaksi grafting dan crosslinking (MBA, APS) pada suhu 70°C, diikuti pengeringan. Karakterisasi meliputi FTIR, pengukuran swelling ratio (SR), uji mekanik (UTM), uji germinasi kecambah, dan analisis pelepasan NPK (Kjehdal, UV–Vis, AAS). Hasil FTIR mengonfirmasi terbentuknya ikatan Si–O–Si, gugus karbonil dan interaksi polimer–NPK. Swelling terbaik dicapai pada 2% wt/v Na?SiO? (SR=147 g/g) dan 10% v/v K-humat (SR=109 g/g). Komposisi dengan silika+NPK menghasilkan SR=123 g/g, sedangkan kombinasi silika+K-humat+NPK SR=99 g/g. Penambahan silika dan K-humat meningkatkan kekuatan tarik dan ekstensi, serta mempercepat pertumbuhan kecambah (hipokotil dan radikula terpanjang pada perlakuan silika+K-humat). Hidrogel menunjukkan perilaku slow-release dengan kumulatif pelepasan konsentrasi N < 5>

This study presents the design and characterization of a composite hydrogel based on natural cellulose derivatives (CMC-Na, HEC) and synthetic polymers (acrylamide, acrylic acid), reinforced with Silika extracted from Paiton PLTU fly ash, potassium humate, and NPK fertilizer for controlled-release agricultural applications. The hydrogel was synthesized via grafting and crosslinking (MBA, APS) at 70°C and subsequently dried. Characterization techniques included FTIR spectroscopy, swelling ratio (SR) measurements, tensile testing, seed germination assays, and NPK release analysis (Kjeldahl, UV–Vis, AAS). FTIR confirmed the formation of Si–O–Si bonds, polymer carbonyl groups, and polymer–NPK interactions. Optimal swelling was observed at 2% wt/v Na?SiO? (SR = 147 g/g) and 10 % wt/v potassium humate (SR = 109 g/g). The formulation with Silika+NPK achieved SR = 123 g/g, while Silika+humate+NPK reached SR ? 99 g/g. The addition of Silika and humate enhanced tensile strength and elongation, and significantly promoted seedling growth (longest hypocotyl and radicle under Silika+humate treatment). Release studies demonstrated a slow-release profile of concentration cumulative release of N < 5>

Kata Kunci : Hidrogel, Fly Ash, K-humat, Pelepasan NPK