A review on adsorption mediated phosphate removal and recovery by biomatrices

Low cost biosorbents have gained considerable importance in the past decade for their removal efficiency of contaminants from wastewaters. Both removal and recycle of the phosphate anion through benign methods are relevant to sustain a steady balance. An attempt has been made to give a comprehensive insight into several physico-chemical factors leading to the adsorption process by various natural biosorbents. Few important facts regarding phosphate biosorption have emerged out as key points viz., pH < pHpzc, high uptake capacity; correlation with Langmuir isotherm model and pseudo second order kinetics; decrease of uptake capacity with longer contact time; enhancement of adsorption process in presence of counter ions, etc. Also, it was noted that the adsorbate: adsorbent ratio is crucial for the removal efficiency of the phosphate ions. A few biosorbents exhibit removal efficiency to a large extent (>95%) although even higher adsorption capacity can be obtained by the modification of the adsorbents. Commercial biomatrices like biochars have shown wide applications for removal of phosphates. Magnetic biochars have shown special performance owing to the presence of iron and a porous nature of their structure. Desorption studies revealed that almost complete recovery of the phosphate ion is possible through simple ion exchange mechanism.

Automated summary

Phosphate ion biosorption is important in wastewater treatment, with key factors including pH, adsorbent: adsorbate ratio, etc. The physico-chemical properties of biosorbents directly affect adsorption efficiency, and the adsorption capacity of phosphate ions can be improved by modifying the adsorbents.