Pengaruh Konsentrasi Asam Sitrat dan Evaporasi Lindi Hitam terhadap Karakteristik Lignin Tandan Kosong Kelapa Sawit

Abstract

Lignin merupakan biopolimer aromatik yang dapat diisolasi dari lindi hitam tandan kosong kelapa sawit (TKKS). Lindi hitam masih mengandung air yang cukup tinggi, sehingga perlu dievaporasi. Penelitian ini menganalisis pengaruh konsentrasi asam sitrat dan pra-perlakuan evaporasi terhadap karakteristik lignin TKKS. Lignin diisolasi melalui proses pengendapan asam sitrat (1M dan 3M). Karakteristik isolat lignin yang dianalisis berupa kadar air, kadar abu, kemurnian lignin, total kadar fenolik, berat ekuivalen, kadar hidroksil fenolik, tipe monomer lignin, kelarutan lignin dalam alkali dan dioksan-air, gugus fungsi, gugus metoksil, dan sifat termal. Lignin hasil isolasi dengan asam sitrat 1M menghasilkan rendemen, kadar air, kadar abu, berat ekuivalen dan kadar gugus metoksil yang lebih rendah dibandingkan asam sitrat 3M. Proses evaporasi dapat meningkatkan rendemen, kadar air, kemurnian, kadar hidroksil fenolik, total kadar fenolik, berat ekuivalen, dan gugus metoksil lignin karena pada suhu 70-80 °C hanya air yang menguap, sementara struktur lignin mulai terdegradasi saat suhu mencapai 300 °C.

Lignin is an aromatic biopolymer that can be isolated from oil palm empty fruit bunch (OPEFB) black liquor. Black liquor still contains a high amount of water, so it needs to be evaporated. This study analyzed the effect of citric acid concentration and evaporation pre-treatment on the characteristics of OPEFB lignin. Lignin was isolated through citric acid precipitation process (1M and 3M). The characteristics of lignin isolates were analyzed in the form of water content, ash content, lignin purity, total phenolic content, equivalent weight, phenolic hydroxyl content, lignin monomer type, lignin solubility in alkali and dioxane-water, functional groups, methoxyl groups, and thermal properties. Lignin isolated with 1M citric acid produced lower yield, water content, ash content, equivalent weight and methoxyl group content than 3M citric acid. The evaporation process can increase yield, moisture content, purity, phenolic hydroxyl content, total phenolic content, equivalent weight, and methoxyl groups of lignin because at 70-80 °C only water evaporates, while the lignin structure begins to degrade when the temperature reaches 300 °C.