Waste Material Adsorbents for Zinc Removal from Wastewater: A Comprehensive Review

Table 2

Comparison among wastewater treatment technologies.

Technique	Advantage	Disadvantage
Chemical precipitation	(i) Simplicity; (ii) Inexpensive capital cost; (iii) Adapted to treat high heavy metal ions concentration	(i) Ineffective when metal ion concentration is low; (ii) Not economical; (iii) Produce large amount of sludge
Ion-exchange	(i) Widely applied for heavy metal removal; (ii) Ion-exchange resins can be regenerated	(i) Secondary pollution can be caused due to regeneration by chemical reagents; (ii) Expensive when treating a large amount of wastewater so cannot be used at large scale
Membrane filtration	High heavy metal ions removal efficiency	(i) High cost and complex process.; (ii) Membrane fouling has limited heavy metal removal
Coagulation-flocculation	Good sludge settling and dewatering characteristics	(i) It involves chemical consumption; (ii) Increased sludge volume generation
Flotation	(i) High metal selectivity; (ii) High removal efficiency; (iii) High overflow rates; (iv) Low detention periods	(i) High initial capital cost; (ii) High maintenance and operation costs.
Electrochemical	(i) Regarded as rapid and well controlled which requires fewer chemicals; (ii) Provide good reduction yields and produce less sludge	(i) Involving high initial capital investment; (ii) Expensive electricity supply
Adsorption	(i) The high cost of AC limits its use in adsorption; (ii) Many varieties of low-cost adsorbents have been developed and tested to remove heavy metal ions; (iii) Biosorption is a relatively new process that has proven very promising for the removal of heavy metal from wastewater	(i) Removal of heavy metals from low wastewater concentration; (ii) Adsorption efficiency depends on the type of adsorbents