Electronic Theses and Dissertation

Tesis ini mengkaji pemanfaatan limbah ampas kopi Gayo sebagai bahan baku karbon aktif dan karbon aktif magnetik (Magnetic Activated Carbon/MAC) untuk adsorpsi zat warna Methylene Blue (MB). Penelitian dilakukan melalui proses karbonisasi, aktivasi kimia menggunakan HCl, dan sintesis MAC dengan metode kopresipitasi menggunakan garam Fe²⁺ dan Fe³⁺. Karakterisasi adsorben dilakukan menggunakan metode standar SNI, FTIR, dan SEM. Uji adsorpsi dilakukan dengan variasi massa adsorben 0,2; 0,4; dan 0,6 gram, waktu kontak 40; 60; 80; dan 100 menit, serta konsentrasi awal MB 5; 10; dan 15 mg/L. Data dianalisis menggunakan model isoterm Langmuir dan Freundlich serta kinetika pseudo orde satu dan pseudo orde dua.
Hasil penelitian menunjukkan bahwa kondisi optimum adsorpsi diperoleh pada massa adsorben 0,6 gram, waktu kontak 80 menit, dan konsentrasi awal MB 5 mg/L. Pada kondisi tersebut, karbon aktif menghasilkan kapasitas adsorpsi sebesar 0,3831 mg/g dengan efisiensi penyisihan 90%, sedangkan MAC menghasilkan kapasitas adsorpsi sebesar 0,3616 mg/g dengan efisiensi 84,95%. Karbon aktif menunjukkan efektivitas adsorpsi sedikit lebih tinggi dibandingkan MAC. Namun, MAC memiliki keunggulan berupa sifat magnetik yang memudahkan proses pemisahan adsorben dari larutan setelah adsorpsi, sehingga lebih praktis untuk diaplikasikan pada pengolahan limbah.
Hasil analisis isoterm menunjukkan bahwa model Langmuir dan Freundlich sama-sama sesuai dengan data adsorpsi. Pada karbon aktif, model Langmuir menghasilkan qₘ sebesar 1,3848 mg/g dan R² sebesar 0,9996, sedangkan Freundlich menghasilkan Kf sebesar 0,5596 dan R² sebesar 0,9790. Pada MAC, model Langmuir menghasilkan qₘ sebesar 1,4372 mg/g dan R² sebesar 0,9490, sedangkan Freundlich menghasilkan Kf sebesar 0,4392 dan R² sebesar 0,9447. Selisih nilai R² menunjukkan bahwa adsorpsi tidak mutlak mengikuti model Langmuir, tetapi melibatkan interaksi fisik dan kimia, dengan model Langmuir yang lebih unggul dalam menggambarkan kesetimbangan adsorpsi.
Hasil analisis kinetika menunjukkan bahwa model pseudo orde dua memberikan kesesuaian lebih baik dibandingkan pseudo orde satu. Pada MAC, nilai R² pseudo orde satu sebesar 0,9377, sedangkan pseudo orde dua sebesar 0,9992. Dengan demikian, proses adsorpsi MB lebih sesuai digambarkan oleh model pseudo orde dua. Penelitian ini menawarkan solusi pengolahan limbah zat warna sekaligus memanfaatkan limbah pertanian menjadi produk bernilai tambah dan berkelanjutan.

This thesis investigates the utilization of Gayo coffee ground waste as a raw material for activated carbon and magnetic activated carbon (MAC) for the adsorption of Methylene Blue (MB). The research was conducted through carbonization, chemical activation using HCl, and MAC synthesis using the co-precipitation method with Fe²⁺ and Fe³⁺ salts. Adsorbent characterization was carried out using standard SNI methods, FTIR, and SEM. Adsorption experiments were performed by varying the adsorbent mass at 0.2, 0.4, and 0.6 g, contact time at 40, 60, 80, and 100 minutes, and initial MB concentration at 5, 10, and 15 mg/L. The adsorption data were analyzed using the Langmuir and Freundlich isotherm models, as well as pseudo-first-order and pseudo-second-order kinetic models. The results showed that the optimum adsorption conditions were obtained at an adsorbent mass of 0.6 g, a contact time of 80 minutes, and an initial MB concentration of 5 mg/L. Under these conditions, activated carbon achieved an adsorption capacity of 0.3831 mg/g with a removal efficiency of 90%, while MAC achieved an adsorption capacity of 0.3616 mg/g with a removal efficiency of 84.95%. Activated carbon showed slightly higher adsorption performance than MAC. However, MAC offers the advantage of magnetic properties, which facilitate adsorbent separation from the solution after adsorption, making it more practical for wastewater treatment applications. The isotherm analysis showed that both the Langmuir and Freundlich models were consistent with the adsorption data. For activated carbon, the Langmuir model yielded a qₘ of 1.3848 mg/g and an R² of 0.9996, while the Freundlich model yielded a Kf of 0.5596 and an R² of 0.9790. For MAC, the Langmuir model yielded a qₘ of 1.4372 mg/g and an R² of 0.9490, while the Freundlich model yielded a Kf of 0.4392 and an R² of 0.9447. The difference in R² values indicates that the adsorption process cannot be attributed exclusively to the Langmuir model but involves both physical and chemical interactions, with the Langmuir model providing a better fit for the adsorption equilibrium. The kinetic analysis showed that the pseudo-second-order model provided a better fit than the pseudo-first-order model. For MAC, the R² values were 0.9377 for the pseudo-first-order model and 0.9992 for the pseudo-second-order model. Therefore, the adsorption of MB was better described by the pseudo-second-order model. This study offers a solution for dye wastewater treatment while valorizing agricultural waste into a value-added and sustainable product.