초록
개시제로 potassium persulfate($K_2S_2O_8$)를 사용하여 methylcellulose(MC)에 중금속 이온과 친화력이 우수한 carboxyl(-COOH)기를 도입하기 위하여 acrylic acid(AA)를 그라프트 공중합시켜 얻어낸 반응생성물(MC-g-AA)을 중금속 이온 흡착제로 적용하였다. MC-g-AA의 그라프트율은 개시제 및 단량체의 농도가 높을수록 증가하였으며 그라프트율 19.7% 이상의 MC-g-AA는 물에 용해되지 않았다. MC-g-AA의 중금속 흡착 특성을 평가하기 위해 MC-g-AA의 기라프트율, 폐수의 pH, 흡착시간, MC-g-AA의 주입량 및 폐수내 $Pb^{2+}$, $Cu^{2+}$ 이온의 농도에 따른 흡착실험을 진행하였다. 흡착실험 결과 MC-g-AA는 pH $4{\sim}6$ 범위에서 $Pb^{2+}$, $Cu^{2+}$ 이온에 대한 높은 흡착량을 나타내었으며 그라프트율 및 초기 중금속 이온의 농도가 높을수록 MC-g-AA의 중금속 흡착량은 증가하였으나 MC-g-AA의 주입량이 늘어날수록 MC-g-AA 단위 무게당 흡착량은 감소하였다. MC-g-AA에 의한 중금속 흡착을 Freundlich 등온흡착 모델로 표현한 $Pb^{2+}$, $Cu^{2+}$ 이온의 l/n은 각각 0.4294, 0.3453로 나타났다.
Graft copolymers were synthesized from methylcellulose(MC) and acrylic acid(AA) with active carboxyl groups in the presence of potassium persulfate($K_2S_2O_8$) initiator to enhance adsorption capacity of toxic heavy metal such as $Pb^{2+}$ and $Cu^{2+}$ from wastewater. The resulting grafted copolymers(MC-g-AA/PAA) were mixture of the graft copolymers from MC and AA(MC-g-AA) and polyacrylic acid homopolymers(PAA). The degree of palling was increased with rising concentration of monomer and initiator under the reaction conditions at $60^{\circ}C$, 3 hrs. The water insoluble property of MC-g-AA showed more than 19.7% degree of grafting. So that it could be an adsorbent of heavy metals. Adsorption characteristics of the MC-g-AA were evaluated depending on the degree of grading, pH of wastewater, adsorption time, dosage of MC-g-AA and concentration of heavy metals in the different conditions. Degree of grafting, and initial concentration of heavy metal ions increased, the adsorption amount of $Pb^{2+}$ and $Cu^{2+}$ increased, but added MC-g-AA increased, the adsorption amount per unit weight of $Pb^{2+}$ and $Cu^{2+}$ decreased. The MC-g-AA showed the high $Pb^{2+}$ and $Cu^{2+}$ adsorption amount in the range pH $4{\sim}6$. Also all of $Pb^{2+}$ and $Cu^{2+}$ ions reached in adsorption equilibrium in neighborhood 4 hours. The adsorption of heavy metals described by Freundlich isotherm, it was determined the value of l/n of $Pb^{2+}$ and $Cu^{2+}$ that 0.4294 and 0.3453, respectively.
