[Adsorption characteristics of Cd2+ and Zn2+ by extracellular polymeric substances with varied constituents from activated sludge].
Three types of extracellular polymeric substances (EPS), EPS1, EPS2 and EP3, with protein/sugar content ratio of 2.5 : 1, 7 : 1 and 9 : 1, respectively, were investigated as sorbent for adsorbing Cd2+ and Zn2+ from wastewater. The experimental results showed that the adsorption efficiency of EPS toward Cd2+ and Zn2+ were dependent on the composition of EPS. The adsorptive capacities of EPS1, EPS2, EPS3 to Cd2+ were 19.5 mg/g, 27 mg/g, 17 mg/g and to Zn2+ 40.5 mg/g, 47.5 mg/g, 37 mg/g, respectively. Kinetic study showed that EPS1 has the highest reaction rate, while EPS2 has the highest adsorption capacity. All of the adsorption processes reached equlibrium within 1 h following both the Freundlich and Langmuir isotherms. The fitted parameters indicated that varied reactions may occur in EPS-metal adsorption process and EPS as adsorbent has much higher adsorption stabilization, adsorption ability and appetency to Zn2+ than to Cd2+. The adsorption capacity of EPS toward Cd2+ and Zn2+ increased with the sugar content, which suggests sugar is of great importance in the adsorption.
Zheng
Lei
L
Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Water Sciences, Beijing Normal University, Beijing 100875, China. budzheng@sohu.com
Ding
Ai-Zhong
AZ
Wang
Jin-Sheng
JS
Tian
Yu
Y
Sun
De-Zhi
DZ
D000327:Adsorption; D001704:Biopolymers / Q000737:chemistry* / Q000302:isolation & purification; D002104:Cadmium / Q000737:chemistry / Q000302:isolation & purification*; D005109:Extracellular Matrix / Q000737:chemistry; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D015032:Zinc / Q000737:chemistry / Q000302:isolation & purification*
D001704:Biopolymers; D012722:Sewage; D014874:Water Pollutants, Chemical; D002104:Cadmium; D015032:Zinc