Adsorption Characteristics Of Excess Sewage Sludge-based Adsorbents

In recent decades, heavy metal pollution for environment is increasing. The heavy metal pollution of water in our country is very outstanding. Adsorption is a kind of important method to remove heavy metal ions pollution in water. But the traditional absorption method is limited by the problems of price, adsorption capacity and processing.Sludge sewage is a solid-liquid mixture containing organic fragments, bacteria, inorganic particles and colloids. It performs an adsorption for heavy metals.However, it is difficult for sewage sludge to be directly used as a heavy metal for industrial sites since it tends to break up and disperse in aqueous solutions. Therefore, sewage sludge based adsorbents with high mechanical strength and adsorption efficiency should be developed.In this work, sewage sludge was cross-linked with epichlorohydrin to increase its mechanical strength and applicability. The effect of the condition of the cross-linking reaction on the mechanical strength and Cu (Ⅱ) adsorption capacity of epichlorohydrin cross-linking sewage sludge (ECS) were investigated. The experimental results showed that cross-linking significantly raise the mechanical strength of sewage sludge. To improve the adsorption capacity of ECS, carboxymethyl cross-linked sewage sludge (CCS) with a maximum adsorption capacity (65mg/g) for Cu (Ⅱ) was synthesized from ECS by using chloroacetic acid as the etherification agent. Kinetic study showed that the adsorption properties of CCS for Cu (Ⅱ) could best be described by the pseudo-second order model and Langmuir model, and the adsorption mechanism was ion exchange.In addition to the adsorption of heavy metal ions in the water, ECS and CCS can also adsorb organic dyes in the waste-water. We successively used methylene blue as an example of organic dyes and explore the adsorption capacity of ECS and CCS to organic dyes in the waste-water. The result showed that they not only had a high adsorption capacity of methylene blue, but also their adsorption sites did not take up the Cu (Ⅱ) ones. This result showed that the ECS and CCS could removal of organic dyes and heavy metals in the waste-water at the same time. Experiments showed that the way of ECS and CCS adsorption for organic dye was divided into two stages, namely fast adsorption phase and slow adsorption phase.In order to solve the problem of the long time of adsorption equilibrium, we use abandoned kelp mixed with sludge sewage to make the SKA(sewage sludge and kelp mixed type adsorbent). After the cross-linking to SKA, we get the heavy metal ion adsorbent SKA-c-Gi and SKA-c-Ei. These two kinds of heavy metal ion adsorbent have high adsorption capacity and good mechanical strength. Compared with CCS, SKA-c-Gi and SKA-c-Ei has the shorter reaction equilibrium adsorption, the simple manufacturing process and the characteristics of the low costs. Through those experiments described in article, we made the excess sewage sludge-based adsorbents named CCS, SKA-c-Gi and SKA-c-Ei, respectively. They are able to realize the excess sludge sewage resource recovery. They have good mechanical strength and high adsorption ability for heavy metal ion. The made of CCS, SKA-c-Gi and SKA-c-Ei provides a new way for excess sludge sewage recycling.