Removal of ammonium, phosphate, and sulfonamide antibiotics using alum sludge and low-grade charcoal pellets.

Powder adsorbents perform well due to their large surface area but are difficult to use because of aggregation and channeling. In this study, pelletization of adsorbents was proposed as a solution to these operating problems. A three-component mixture was extruded into pellets and calcined under air or nitrogen conditions The pellet adsorbent removed 47, 71, 97, and 72% of ammonium, phosphate, sulfathiazole, and sulfamethoxazole, respectively. Bentonite improved greatly the strength of pellets, and a 10 wt% of bentonite was sufficient to maintain pellet shape and mass. No significant difference in individual adsorption and multi-pollutant adsorption was found. Pellet adsorbents with alum sludge, bentonite, and low-grade charcoal are low-cost materials that effectively remove multi-pollutants from the aqueous phase.

Pelletized adsorbent of alum sludge and bentonite for removal of arsenic.

Powder adsorbents show an excellent adsorption capacity for arsenic(As) due to the large specific surface area. However, the performance of powder adsorbents decreases significantly by channeling in the adsorption bed, and the powder is released from the bed. Pelletization of power adsorbent can solve the problems, and bentonite was proposed as a binder to improve the strength. The adsorption capacity and lifetime of pelletized adsorbent were evaluated through a batch and column study. The addition of bentonite decreased adsorption capacity by 16% of pellet without bentonite, but improved compressive strength of adsorbent up to 3.6 times. In the batch test, the maximum adsorption capacity of pelletized adsorbent is 22.2 mg As/g, which is about 40% of powder adsorbent. However, in the column study, pellet adsorbent showed similar adsorption performance and lifetime to commercial and powder adsorbent. As a result, the pellet adsorbent using bentonite is a potential low-cost adsorbent to remove effectively As in the aqueous phase.