Study On Deactivation Of Heavy Metals In Sludge By Purified Heat-activated Attapulgite

As the world population increasing quickly and economy growing fast, theproblem ofenvironmental pollution has become increasingly worse. In recent years,many municipalsewage treatment plants have been built, which effectively alleviate thepollution of waterenvironment caused by the discharge of municipal sewage andindustrial wastewater. At thesame time,a large amount of sewage sludge producedduring the process of sewage treatmentmay result in second pollution to theenvironment. Since there are high quality of nutritionelements such as nitrogen,phosphorus and kalium, the agricultural utilization of sewagesludge is become animportant topics in nowadays research. However, the heavy metals insewage sludge arethe key factor restricting the utilization of sewage sludge in agriculture.Many studieshave been made to decrease and reduce the poisonous effect of the heavy metalsinsewage sludge, but the characters of system, economy and utility still cannot meetpracticaldemands. Therefore, research on the removal of the heavy metal and theutilization of sewagesludge in agriculture has a very important significance. Heavy metals in biological activity,mobility depends not only on the total amount, in the form of heavy metals depends largelymore.Attapulgite is a family of2:1affiliated sepiolite magnesium aluminum silicate minerallayer chain, attapulgite developed within the pore and large specific surface area, with goodadsorption, can serve as a good adsorbent attapulgite has gradually become an importantmaterial for the passivation of heavy metals.The components and chemistry character ofGuilin city’s sewage sludge areanalysed. It is shown that the sewage sludge’s nutrition canfully meet the standard ofagricultural utilization. add attapulgite clay in the sludge toeffectively remove and reduce urban toxic heavy metals in sludge for the purpose, content ofheavy metals in sludge and form changes were analyzed. Attapulgite is a family of2:1affiliated sepiolite magnesium aluminum silicate mineral layer chain, attapulgite developedwithin the pore and large specific surface area, with good adsorption, can serve as a goodadsorbent attapulgite has gradually become an important material for the passivation of heavymetals.Experiment by adding attapulgite mixed with sludge pile, the measured sample Ph, ECvalues, Cu, Ni, Cd and Zn four kind of full amount of heavy metals, as well as four kinds ofwater soluble heavy metals, DTPA extractable content and form distribution of BCRResearch attapulgite clay inactivation of sludge. The experiment was designed according todifferent amounts of attapulgite seven experiments, mixed stacked30days, at the beginningof the process were mixed,10days,20days,30days, sampling, analysis of four heavy metalcontent of sludge and morphological changes attapulgite clay determine heavy metals insludge and the best ratio of stacked passivation time. Experimental results show that the addition of attapulgite affect sludge Ph, EC value, thetotal amount of heavy metal concentrations are smaller, water soluble, DTPA extractablecontent have undergone different degrees of reduction. Another form of heavy metaldistribution of the various BCR shift, with the added after a certain proportion of attapulgiteclay, Cu, Ni, Cr, Zn have demonstrated a certain degree of passivation effect, namely thetransition from stable to unstable form shape. In attapulgite dosing ratio was15%, stacking20days, unstable Cu and Ni to form a stable form transformation is most obvious, Cr in thedosing ratio is10%,20days unstable stacking form the largest transformation, Zn in thedosing ratio is30%, the amount of conversion stacked30days maximum unstable form.Through seed germination experiment, adding15%,30%heat-modified attapulgite clay afterpiling up20days to30days, the best cabbage seed development status, this migration andmetals speciation are consistent with BCR assessment results.