Penelitian ini bertujuan menguji filter arang aktif gambut dalam menyerap logam berat mercury (Hg) pada air sungai Kahayan yang tercemar. Proses pembuatan arang aktif melalui beberapa tahap yaitu: tahap karbonisasi, tahap penghalusan, dan tahap pengaktifan secara fisika. Mutu arang aktif mengacu pada persyaratan SNI 06-3730-1995 meliputi kadar air dan kadar abu. Hasil uji mercury analyzer menunjukkan bahwa arang aktif gambut mampu menyerap logam berat mercury (Hg) dalam air. Kadar logam berat mercury (Hg) berkurang setelah dilakukan proses adsorbsi yaitu sebagai berikut: ukuran serbuk gambut 40 mesh mampu menyerap logam berat mercury (Hg) sebesar 50 % ; ukuran serbuk gambut 60 mesh d mampu menyerap logam berat mercury (Hg) sebesar 75%.Kata kunci: arang aktif; gambut; logam berat; mercuryPeat Activated Charcoal as a Heavy Metal Mercury (Hg) Filter ABSTRACTThis study aims to test the activated peat charcoal filter to absorb heavy metal mercury (Hg) in polluted Kahayan river water. The process of making activated charcoal goes through several stages, namely: the carbonization stage, the refining stage, and the physical activation stage. The quality of activated charcoal refers to the requirements of SNI 06-3730-1995 including moisture content and ash content. The results of the mercury analyzer test showed that peat-activated charcoal was able to absorb heavy metal mercury (Hg) in water. The heavy metal mercury (Hg) content was reduced after the adsorption process was carried out, namely as follows: the size of 40 mesh peat powder can absorb heavy metal mercury (Hg) by 50%; Peat powder size of 60 mesh can absorb 75% of the heavy metal mercury (Hg).Keywords: activated carbon; peat; heavy metals; mercury