Influence of Na+, K+, Mg2Â +, Ca2Â +, and Fe3Â + on filterability and settleability of drilling sludge

The raw sludge has colloidal stability, which plays an important role in solid-liquid separation of sludge. The particles of drilling sludge carry high negative surface charge, resulting in repulsion of adjacent particles. The stability inhibits sludge flocculation and leads to poor filterability and settleability. After the addition of inorganic cations, the presence of cations neutralizes the negative charge of sludge by providing positive charge. The reduction in sludge negative charge decreases repulsion forces and affects the degree of sludge dispersion. The colloidal stability is destroyed and sludge particles congregate with each other to different extent. Therefore, different inorganic cations improve filterability and settleability by this means.95