Effects of pH and dosages of montmorillonite on the carbon, nitrogen, phosphorus and heavy metals adsorption from biogas slurry

Montmorillonite was used as adsorption material to study the effects of different dosages and pH on COD, TP, TN, NH4 + -N, Zn, Cu, Cr, As, Mn and Ni of biogas slurry, and the interaction between physicochemical properties and heavy metals of biogas slurry was clarified. The results showed that the adsorption capacity of COD, TN, NH4 + -N, TP, Zn and Cu in biogas slurry decreased with the increase of the montmorillonite dosage of 0~50 g/L, and the removal rate increased and then tended to be balanced. At the dosage of 30 g/L, the adsorption effect was better. Under the proper condition with pH of 6.5~9.5, montmorillonite can effectively absorb TP, Zn and Cu in biogas slurry, with maximal removal rate of 84.3%, 86.8% and 94.5%, and it has a poor adsorption effect on TN, NH4 + -N and Cr. According to the adsorption capacity and removal rate, the appropriate pH of montmorillonite adsorbing biogas slurry was 7.5~8.5. Zata potential was significantly negatively correlated with COD, TP, TN, NH4 + -N, Zn, Cu, Ni. The strongest positive correlation was presented between Zn and Cu, and Cr and pH in biogas slurry. Cr and TP had a negative remarkably relationship, and Cr and As was not significantly correlated.