STUDI ADSORPSI KOMPETITIF KADMIUM(II) DAN SENG(II) DENGAN GREEN ADSORBEN – ASAM HUMAT TINJA SAPI

AMELIA H BURHAN, Prof. Bambang Rusdiarso, DEA.

2014 | Tesis | S2 Ilmu Kimia

Tinja sapi menunjukkan kemampuannya sebagai green source asam humat, karena merupakan sumber yang renewable dan tidak berpotensi merusak lingkungan. Ekstraksi asam humat tinja sapi dilakukan sedikit modifikasi metode ekstraksi alkali. Proses pemurnian asam humat tinja sapi mengikuti proses pemurnian yang biasa digunakan pada asam humat gambut, yaitu dengan menggunakan larutan 0,1M HCl/0,3M HF (1:1). Asam humat tinja sapi selanjutnya digunakan sebagai adsorben untuk mengkaji adsorpsi Cd(II), Zn(II), dan adsorpsi kompetitif antara Cd(II) dan Zn(II). Aspek adsorpsi yang dipelajari meliputi pengaruh berat adsorben, pH medium adsorpsi, laju adsorpsi, pola isoterm, kapasitas, dan energi adsorpsi. Telah dihasilkan 6 jenis asam humat tinja sapi. Berdasarkan hasil penentuan kandungan gugus fungsional, kemampuan adsorpsi, dan tinjauan aspek kimia hijau, diketahui bahwa asam humat tinja sapi tanpa proses pemanasan dan tanpa pemurnian menunjukkan hasil terbaik. Adsorpsi Cd(II) dan Zn(II) menggunakan AHTS, optimum pada pH 5 dan mengikuti pola isoterm Langmuir dengan energi adsorpsi masing-masing sebesar 20,92 dan 22,32 kJ/mol. Laju adsorpsi Zn(II) lebih cepat dibandingkan laju adsorpsi Cd(II), berturut-turut adalah 1,06x10-4 dan 4,12x10-5 g/mg menit. Kapasitas adsorpsi Cd(II) adalah 8,85x10-4 mol/g sedangkan kapasitas Zn(II) adalah 8,18x10-4 mol/g. Studi kompetitif antara Cd(II) dan Zn(II) pada asam humat tinja sapi menunjukkan bahwa jumlah Cd(II) teradsorpsi AHTS lebih banyak daripada Zn(II). Hal ini dikarenakan ikatan Zn(II) dan situs aktif AHTS lebih polar sehingga meningkatkan kelarutannya, akibatnya jumlah Zn(II) teradsorpsi AHTS lebih kecil dibandingkan Cd(II). Kata Kunci: asam humat, tinja sapi, adsorpsi, adsorpsi kompetitif, kinetika, isoterm, kadmium, seng

Cow dung shows their ability as a green source of humic acid, because it’s a renewable source and it doesn’t potentially damage environment. Cow dung humic acid extraction was performed by slightly modification of alkaline extraction methods. Cow dung humic acid purification is exactly the same with peat humic acid purification. This used 0.1M HF/ 0.3M HCl (1:1). Cow dung humic acid was then used as adsorbent to study adsorption of Cd(II) and Zn(II), as well as competitive adsorption between Cd(II) and Zn(II). The adsorption aspects studied were adsorbent weight effect, optimum pH, rate, pattern, energy, and capacity of adsorption. Six types of cow dung humic acid were produced. Based on the determination results of functional groups, adsorption capacity, and green chemistry aspects, it was found that cow dung humic acid without heating and purification process showed the best result. Adsorption of Cd(II) and Zn(II) using cow dung humic acid followed Langmuir Isotherm, with adsorption energy of 20.92 and 22.32 kJ/mol, respectively. Zn(II) adsorption rate was higher than that of Cd(II), i.e. 1,06x10-4 g/mg min for Zn(II) and 4,12x10-5 /mg min for Cd(II). Cd(II) and Zn(II) adsorption capacity were 8.85x10-4 and 8.18 mol/g, respectively. The competitive study between Cd(II) and Zn(II) on cow dung humic acid showed that the concentration of Cd(II) adsorbed by cow dung humic acid was greater than that of Zn(II). This was due to higher polarity binding between Zn(II) and cow dung humic acid active sites, resulting in its solubility increased, thus the concentration of Zn(II) adsorbed by cow dung humic acid was smaller than that Cd(II). Keyword : humic acid, cow dung, adsorption, competitive adsorption, kinetic, isotherm, cadmium, and zinc

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