Calcium and hydrogen effects during sorption of copper onto an alginate-based ion exchanger: Batch and fixed-bed column studies

Removal of copper and cadmium in acid mine drainage using Ca-alginate beads as biosorbent

“…The ionotropic gelation phenomenon of Ca-alginate beads can be described using the 'egg box' model, in which a divalent cation binds to two carboxyl groups on the adjacent alginate molecules ( Fig. 1) (Kashima and Imai, 2012;Liu et al, 2012;An et al, 2013). Biosorption mechanisms of Ca-alginate for heavy metals are commonly known to be ion exchange and precipitation (or complexation) processes (Romero-Gonzalez et al, 2001;Davis et al, 2003;Shin et al, 2007).…”

“…Other cost effective biosorbents using immobilized biomass in a granular or polymeric matrix have also been used to remove heavy metals from solution (Kumar et al, 2011;Seo et al, 2013). Alginate has been generally used as the biosorbent material; it contains dead biomass that removes heavy metals from aqueous solutions for the following reasons: (1) high sorption capacity, (2) high mechanical strength in its reacted solid form (i.e., calcium alginate), (3) high chemical stability for recycling, and (4) hydrophilicity (Bhat and Aminabhavi, 2006;Lagoa and Rodrigues, 2009;An et al, 2013). Alginate is composed of heteropolymer linked D-mannuronic acid and L-guluronic acid, which are mostly obtained from brown algae (Chung, 2007).…”

“…Therefore, remediation processes for AMD have been limited to physical and chemical methods such as chemical precipitation, coagulation, and membrane processes, in spite of the high cost of operation and the difficulty of treating sludge with such methods (Abu Al-Rub et al, 2004;Kiran et al, 2005;Prasad and Mortimer, 2011). Recently, the use of alginate refined from seaweed as a biosorbent has been attempted for the removal of heavy metals from aqueous solutions in neutral pH environments due to its high sorption capacity, high mechanical strength in reacted solid form, and high chemical stability for recycling (Bhat and Aminabhavi, 2006;Lagoa and Rodrigues, 2009;An et al, 2013).…”

“…Many studies have been performed to remove heavy metals from wastewater using biological methods such as biosorption, bioprecipitation, and biouptake (Raskin and Ensley, 2000;Rehman and Anjum, 2010;Degefu and Dawit, 2013;Milojković et al, 2014). Even though biopolymers such as alginate, chitosan/chitin, seaweed, and dead biomass can be used in advantageous removal processes with high reactivity and less toxicity, most of these biological processes may be not commercially feasible for AMD treatment because of difficulties in maintaining low pH conditions (pH < 3) (Costa et al, 2008;Chatterjee et al, 2010;An et al, 2013;Olds et al, 2013). Therefore, remediation processes for AMD have been limited to physical and chemical methods such as chemical precipitation, coagulation, and membrane processes, in spite of the high cost of operation and the difficulty of treating sludge with such methods (Abu Al-Rub et al, 2004;Kiran et al, 2005;Prasad and Mortimer, 2011).…”

Biosorbent encapsulation in calcium alginate: Effects of process variables on Cr(VI) removal from solutions

“…During the hardening process, Ca 2+ cations from the curing solution (CaCl 2 ) interact with the alginate by a sodium-calcium exchange mechanism. The time inside the hardening solution and the amount of biomaterial trapped in the alginate gel influence this exchange [31]. The fine particles of the biomaterial can limit the sodium-calcium exchange process and thus decrease the number of free binding sites for Ca 2+ cations [32].…”