Impact Of Humic Acid On The Adsorption Of Copper Ion By Activated Sludge

Using activated sludge adsorption to remove copper ion is one of the hotspots in wastewater treatment field. The humic acid(HA) in environment will have an impact on the adsorption of copper ion onto activated sludge because of complexation of copper ion. Therefore, activated sludge adsorption of copper ion in the presence of HA was studied in this paper. Factors affecting the adsorption of copper ion by activated sludge, such as contact time, p H, concentrations of activated sludge, copper ion and HA, temperature, salinity, hardness and different adding orders, were investigated. It also had a preliminary understanding of the mechanism that effect of HA on copper ion removal in activated sludge system through dynamic analysis, thermodynamic analysis and Fourier transform infrared spectroscopy(FTIR). The main conclusions achieved were listed as follows.① HA had some effect on the adsorption of copper ion by activated sludge. When p H=6 and the concentration of copper ion and activated sludge were 2 mg/L and 2.0 g/L, respectively, the adsorption process reached balance in 60 min. While the balanced time prolonged 30 min and the adsorption capacity of activated sludge increased 0.0396 mg/g after adding HA. And at p H=6, the adsorption rates of copper ion in the systems of both with HA and without HA reached the maximum value of 84.3% and 82.9%, respectively. When the activated sludge concentration was in the range of 0.5~1.97g/L, the adsorption capacity of activated sludge increased 0.11~0.48mg/g after adding HA. While the activated sludge concentration was in the range of 1.97~4.36g/L, the adsorption capacity of activated sludge only increased 0.025~0.11mg/g after adding HA. When the concentration of copper ion was 50mg/L, the adsorption rates were the highest regardless of whether there was HA in the system.In systems of HA and activated sludge as adsorbent separately or collaboratively as adsorbent, the adsorption rates increased as the temperature rose from 10℃ to 30℃. In addition, the electric double layer compression of Na+ and the adsorption bridging by Ca2+ had an impact on the adsorption. Though the effect of HA concentration and different adding orders were not obvious on the adsorption result, adding humic acid can promote the adsorption of copper ion by activated sludge indeed.② Adsorption processe of copper ion by activated sludge were coincident with the pseudo second dynamics kinetic and the theory adsorption capacity in the systems with HA and without HA were 0.898mg/g and 0.914 mg/g, respectively. And the adsorption processes fitted well with Freundlich equation. The calorific values of activated sludge, HA and both for the adsorption of copper ion were in the range of 0.802~2.889 k J.mol-1. And it could be inferred that the main adsorption mechanism might be hydrogen bond and dipole force.FTIR showed that-OH group and benzene ring were in relation with the adsorption of copper ion onto HA. And-OH group and-COOH group were mainly related to adsorption of copper ion onto activated sludge with absence of HA. While C-O group in polysaccharides and lipids as well as C-H group in benzene substances were in relation with the adsorption of copper ion onto activated sludge in the presence of HA.