Recovery of copper and silver from industrial e-waste leached solutions using sustainable liquid membrane technology: a review.

Waste electrical and electronic equipment or e-waste has recently emerged as a significant global concern. This waste contains various valuable metals, and via recycling, it could become a sustainable resource of metals (viz. copper, silver, gold, and others) while reducing reliance on virgin mining. Copper and silver with their superior electrical and thermal conductivity have been reviewed due to their high demand. Recovering these metals will be beneficial to attain the current needs. Liquid membrane technology has appeared as a viable option for treating e-waste from various industries as a simultaneous extraction and stripping process. It also includes extensive research on biotechnology, chemical and pharmaceutical, environmental engineering, pulp and paper, textile, food processing, and wastewater treatment. The success of this process depends more on the selection of organic and stripping phases. In this review, the use of liquid membrane technology in treating/recovering copper and silver from industrial e-waste leached solutions was highlighted. It also assembles critical information on the organic phase (carrier and diluent) and stripping phase in liquid membrane formulation for selective copper and silver. In addition, the utilization of green diluent, ionic liquids, and synergist carrier was also included since it gained prominence attention latterly. The future prospects and challenges of this technology were also discussed to ensure the industrialization of technology. Herein, a potential process flowchart for the valorization of e-waste is also proposed.

Emulsion liquid membrane modeling for chromium removal from electroplating wastewater using TOMAC as a carrier.

Hexavalent chromium, emanating primarily from the electroplating industries, can be reduced to the less toxic trivalent variety by several methods, including emulsion liquid membrane (ELM). In this work, studies on the continuous removal of chromium from authentic electroplating wastewater by ELM are reported. The effects of treat ratio, external feed phase, and stripping agent concentration were examined. A mathematical boundary breakage model was used to study the extraction efficiency of chromium through the ELM process. The model representing the prediction of ELM extraction performance for chromium was validated through the comparison between the simulation and experimental results. The result showed the simulation model is found to be in good agreement with the experimental result. Almost 100% of 40 ppm chromium in the external feed phase was extracted within 3 to 5 min using 0.022 M TOMAC as extractant, 1.0 M acidic thiourea in the internal phase, and 1 to 5 of treat ratio. PRACTITIONER POINTS: Hexavalent chromium, emanating primarily from electroplating industries, can be reduced to the less toxic trivalent using ELM process. The developed method was tested for its applicability with predominant species of Cr2 O7 2- in real rinse electroplating wastewater. The extraction efficiency (%) of Cr (VI) was almost 100% for 40 ppm Cr in the external feed phase within 3 to 5 min. The result showed the simulation model is found to be in good agreement with the experimental result.

Selective extraction and recovery of polyphenols from palm oil mill sterilization condensate using emulsion liquid membrane process.

Polluted sterilization condensate discharged from palm oil mill may contain polyphenols that are rich in the antioxidant property. Emulsion liquid membrane (ELM) process is a promising method for polyphenol recovery due to its several attractive features such as high selectivity, simple operation, and low energy consumption. In this study, the condensate was characterized to determine its total phenolic content (TPC), ionic elements, and pH. ELM formulation containing tributylphosphate (TBP) as a carrier, kerosene as a diluent, sorbitan monooleate (Span 80) as a surfactant, and sodium hydroxide (NaOH) as a stripping agent was developed. The results show that sterilization condensate contains 700-1500 mg GAE/L of TPC. During the ELM process, more than 91% of extraction with 83% recovery and 8.3 enrichment were achieved at the favorable condition of 0.1 M TBP, external phase pH 5, 1 M NaOH, 1:5 treat ratio, 5% v/v of octanol as a modifier, and 100 mg GAE/L external phase concentrations. Thus, ELM offers a potential alternative technology to extract and recover polyphenols from palm oil mill sterilization condensate while contributing to sustainable production. Graphical abstract Extraction of polyphenols from palm oil mill sterilization condensate using ELM process.

Supported liquid membrane extraction of nickel using stable composite SPEEK/PVDF support impregnated with a sustainable liquid membrane.

A sustainable and stable supported liquid membrane (SLM) extraction of nickel was developed via impregnation of sustainable liquid membrane in the composite membrane support consisting of polyvinylidene fluoride (PVDF) and sulfonated poly (ether ether ketone) (SPEEK). Bis-2-ethylhexyl phosphate (D2EHPA), 1-octanol, refined palm oil and sulfuric acid were employed as extractant, synergist extractant, diluent and strippant, respectively. Variables studied including effect of refined palm oil compositions as well as the configurations and thicknesses of SPEEK. Lifespan of SLM was evaluated by recycling the composite membrane support. Results revealed that upon using 100% refined palm oil, about 100% of nickel was extracted and recovered in 10 and 14 h, respectively. Composite SPEEK/PVDF stabilized SLM by reducing liquid membrane loss from 47 to 23% upon applying SPEEK at the feed side of PVDF support. High permeability and flux values were obtained at 9.26 x 10-4 cms-1 and 6.48 x 10-7 molcm-2s-1 when increasing SPEEK thickness from 0.025 to 0.055 mm, respectively. The lifespan of SLM was extended up to ninth cycles with low weight loss percentage of the impregnated composite membrane (8%). In conclusion, the SPEEK/PVDF impregnated with refined palm oil has improved the stability of SLM extraction of nickel ions from industrial wastewater.

Simultaneous extraction and enrichment of reactive dye using green emulsion liquid membrane system.

Currently, an extractive green palm oil-based emulsion liquid membrane (ELM) has been used for simultaneous extraction and enrichment of Reactive Red 3BS from simulated synthetic dye wastewater. The ELM consists of two main phases, which are organic liquid membrane (LM) and stripping solution. During the extraction process, the ELM was dispersed into the simulated synthetic dye wastewater containing the Reactive Red 3BS complexes. The organic LM contains tridodecylamine (TDA), Sorbitan Monooleate (Span 80) and palm oil as a carrier, surfactant and diluent, respectively. The sodium bicarbonate (NaHCO3) was used as stripping solution for the enrichment process. Several important parameters that affected the simultaneous extraction and enrichment of Reactive Red 3BS, such as carrier and stripping agent concentrations, extraction time and treat ratio, were investigated. The results showed that almost 90% of Reactive Red 3BS ions were successfully extracted with 10 times enrichment in the stripping phase at the optimum conditions of 0.2 M TDA, 0.1 M NaHCO3, 5 min of extraction time and 1:5 of treat ratio. Hence, it can be concluded that palm oil possesses a high potential as green diluent in future technology, especially in ELM process for the removal and recovery of Reactive Red 3BS from synthetic dye wastewater.

Synergistic green extraction of nickel ions from electroplating waste via mixtures of chelating and organophosphorus carrier.

The discharge of electroplating waste containing nickel ions has led to environmental issues owing to the toxicity problem mainly to the aquatic organisms and humans. Liquid-liquid extraction offers a great potential treatment for nickel removal with several advantages of simple, high efficiency and high separation factor. In this study, a green synergistic liquid-liquid extraction of nickel ions from electroplating waste solution using chelating oxime (LIX63) and organophosphorus (D2EHPA) carriers individually as well as their synergistic mixture has been studied. The result demonstrated that about 83% of nickel ions have been successfully extracted via the mixture system of 0.08M LIX63 +0.02M D2EHPA with the maximum synergistic enhancement factor, Rmax of 29.56. Meanwhile, the back extraction study also revealed that HNO3 was the most suitable stripping agent while the diluent screening also showed that palm oil has high potential to be incorporated as a diluent in the green synergistic liquid-liquid extraction of nickel.

Recovery of kraft lignin from pulping wastewater via emulsion liquid membrane process.

Kraft lignin (KL) is a renewable source of many valuable intermediate biochemical products currently derived from petroleum. An excessive of lignin comes from pulping wastewater caused an adverse pollution problems hence affecting human and aquatic life. A comprehensive study pertaining to emulsion liquid membrane (ELM) extraction of lignin from pulping wastewater was presented. ELM formulation contains Aliquat 336 as carrier, kerosene as diluent, sodium bicarbonate (NaHCO3 ) as stripping agent and Span 80 as surfactant. The emulsion stability was investigated at different surfactant concentrations, homogenizer speed and emulsification time. Modifier (2-ethyl-1-hexanol) was added to avoid segregation of third phase while improving the emulsion stability. At optimum conditions, 95% and 56% of lignin were extracted and recovered, respectively at 10 min of extraction time, 0.007 M of Aliquat 336, 0.1 M of NaHCO3 and 1:5 of treat ratio. Additional of modifier was contributed to highest recovery up to 98%. The ELM process was found to be equally feasible and quite effective in the recovery of KL from real pulping wastewater. Therefore, ELM process provides a promising alternative technology to recover KL from pulping wastewater while solving the environmental problems simultaneously.

Selective removal and recovery of Black B reactive dye from simulated textile wastewater using the supported liquid membrane process.

Effluent containing colour/dyes, especially reactive dyes, becomes a great concern of wastewater treatment because it is toxic to human life and aquatic life. In this study, reactive dye of Black B was separated using the supported liquid membrane process. Commercial polypropylene membrane was used as a support of the kerosene-tridodecylamine liquid membrane. Several parameters were tested and the result showed that almost 100% of 70 ppm Black B was removed and 99% of 70 ppm Black B was recovered at pH 2 of the feed phase containing 0.00001 M Na2SiO3, flow rate of 150 ml/min and 0.2 M NaOH. The membrane support also remained stable for up to 36 hours under an optimum condition.