Table 8.

Technologies for the recovery of valuable substances from different industrial wastewater

S.No	Industry sectors	Valuable products recovered		Technical method applicable for recovery	Advantages	Disadvantages	References
		Recovery of valuables (metals, solvents)	Recovery of process streams (electrolytes, inorganic acids)
1	Electrical power plants	Non-ferrous metals like copper, zinc, tin etc. and	Cr, Zn—electrolytes,	Chemical oxidation, reduction	High reaction rates, provides complete mineralization of organic compounds	Operational problems as other reference electrodes are used	Liu M et al. (2018)
2	Nuclear power plants	Uranyl nitrate (for the conversion of uranium to fuel)—using tributyl-phosphate	Boric acid, polyantimonic acid, hydrous titanium oxide (inorganic sorbents used for treatment of radioactive waste streams)	Selective ion exchange	Selective removal of specific radionuclides, low cost, no addition of chemicals	Large pH changes in the production process, time consuming	Ohto H et al. (2017)
3	Mining	Gold, silver, copper, nickel, niobium, tantalum, cobalt, zinc, zirconium & other rare earth elements	Glutaric acid (from leaching process), H2SO4	Extraction and using special adsorbents	Highly effective process with rapid kinetics	Expensive	Mfune O et al. (2018)
4	Ceramics	Tantalum, niobium oxide—using liquid membranes	Solvents like xylene present in acrylates, epoxies, etc.	Cementation	Controlled potential permits for the separation of precious metals, effective when carried out by reduction with metallic iron	Excess conciliatory metal consumption	Jouhara H et al. (2021)
5	Pharmaceutics	Acetone, hexane, isopropanol	Electrolytes like sodium chloride, calcium gluconate	Chromatography	High accuracy, precision, recovery	Since the eluent is itself an electrolyte, it is difficult to determine the separated analytes against eluent	Savelski MJ et al. (2017)
6	Food	Deep eutectic solvents like choline chloride with glycerol, phenyl acetic acid that is used for the separation of organic compounds such as phenolic, aromatic, sugars, flavonoids from food samples	Nitric acid (mineral acid), hydrochloric acid, lactic acid, etc.	Crystallization and evaporation	Low temperature and less energy requirement	Yield is limited by phase equilibrium	Hernández K et al. (2021)
7	Machinery	Oils	Acetone, hexane, xylene, methyl ethyl ketones, alcohols	Resin adsorption	High capacity and selectivity of the resin	Excess rinse time and migration of cation resin into anion unit can cause leakage problems	Dutournié P et al. (2019)
8	Organic chemicals	Organic solvents like acetone, isopropanol, methanol, methanol, ethanol, hexane	Inorganic acids such as HCl, HNO3, H2SO4	Acid and ion retardation	High accuracy, recovery and regeneration limits the emission of harmful gases	High energy consumption, lack of selectivity towards heavy metals	Wang S et al. (2019)
9	Agriculture	Special metals like lead, chromium, arsenic, zinc, cadmium, copper, nickel, etc.	Sodium sulfate, hydrofluoric acid (applied in the production of insecticide and fertilizer)	Sulfide and organosulfate precipitation	Highly efficient towards heavy metals and feasible	Formation of oligomers	Xu M et al. (2021)
10	Battery manufacture	Metals and metal-oxide such as nickel, lithium, cobalt-oxide	Electrolytes like NaCl, KCl	Hydroxide-precipitation	Low cost of execution, simple process, easy pH adjustments	Low solubility of the metal, sensitive to the concentration of precipitating agent	Chanthapon N et al. (2017)
11	Petrochemicals	Hexane, ethanol, methanol, acetone and precious metals like platinum, palladium, rhenium (from the spent catalyst)	Hydrochloric acid	Electrochemical recovery	No chemical addition, high efficiency, possibility for energy and resource recovery	Anode inactivation may happen	Santos PG et al. (2020)
12	Textile	Heavy metals like Cd, As, Pb, Cu, etc. and chlorinated solvents	Acid, reactive and direct dyes using anion exchange resins	Bulk solids and fabrics filtration, nanofiltration, adsorption	Ease of operation, reliable, low power consumption, high efficiency	Expensive regeneration process	Thamaraiselvan C et al. (2018)
13	Metal refinery	Gold, silver, platinum, and other metals like Cd, Mo, Pb, Ni, etc.	Tartaric acid, acetic acid, EDTA	Flotation	Efficient separation, applicable for low grade embedding	Causes environmental pollution, finer grinding particle size is needed	Garole DJ et al. (2018)
14	Solar industry (photovoltaics)	Metals like silicon, silver, copper, aluminium, etc.	Hydrohalic acid	Sedimentation and centrifugation	Labor-intensive, short harvesting times	Less flexibility and suitable for larger volumes	Igoud S et al. (2021)
15	Iron and steel	Manganese, iron, aluminium, silicon, titanium, vanadium, etc.	Sulphuric acid, butyric acid, and other organic and mineral acids	Flocculation and precipitation	Process simplicity and integrated physicochemical technique	Not cost-effective, system controls are required	Wang LP et al. (2019)
16	Semiconductor s	Metalloids such as antimony, selenium, gallium, germanium, etc.	Sodium chloride, poly-ethylene terephthalate (PET)	Electrodialysis	Property of polarity reversal allows to perform in the absence of chemicals	Ion diffusion is non-linear to applied voltage after certain current density	Eng CY et al. (2019)
17	Dairy	Heavy metals like lead, chromium and trace elements like zinc, copper, iron	Citric acid, ammonium molybdate, potassium antimony tartarate, lactic acid, etc.	Diffusion dialysis	Uniformity, optimum performance, low neutralization costs	High operational cost and high consumption of water and energy	Brião V. B et al. (2019)
18	Leather	Synthetic tanning agents such as formaldehyde, glutaraldehyde, phenols, acrylates, etc., sulfonated oils, metals like cerium, manganese, chromium, aluminium	Formic acid, phosphoric acid, nitric acid (which are complexing agents for the removal of chromium from leather scraps)	Distillation and rectification	Energy saving operation, less theoretical stage requirements	High operating costs	China CR et al. (2020)
19	Paper and pulp	Carbon, disulfide methanol, acetone, methanol (used for wood-chips digestion, spent liquor evaporation)	Potassium nitrate, nitric acid, sulphuric acid, saccharinic acid, resin acid, formic acid	Activated carbon adsorption	Provides high surface area and significant stability	Product recovery requires special, expensive distillation/ extraction	Elakkiya E et al. (2020)
20	Oil extraction	Metal halides like stannous chloride and crude oil	Polyacrylic acid,	Reverse osmosis	Separation of dissolved substances, cost-effective	Possibility of fouling since it is a membrane-based technique	Chang H et al. (2019)