Simple gold recovery from e-waste leachate by selective precipitation using a quaternary ammonium salt

Precipitation processes, if selective, present a simple and economical alternative for the recovery of critical metals from primary and secondary ores including electronic wastes. In this work, the recovery of gold by precipitation from both mono-elemental solutions and real CPU leach solution was demonstrated using hydrophilic quaternary ammonium salts. The gold precipitation yield is shown to be dependent on the apolar volume of the precipitant, with the addition of tetrabutylammonium-based salts resulting in the recovery of over 90 % of gold from synthetic solutions. The origin of gold precipitation selectivity relative to common metal ions upon addition of tetrabutylammonium nitrate ([N4444][NO3]) was assigned by X-ray crystal structure to the formation of size selective apolar cavity between neighbouring [N4444]+ cation and the [AuCl4]- anion. Following optimisation as a function of the gold to precipitant molar ratio, aqua regia concentration and time, approximately 70 % of gold could be recovered from waste CPU leach solution with a final purity of 91.4 % (mol/mol). [N4444][NO3] proved to be a versatile gold extractant and could be further applied as part of an acidic aqueous biphasic system at higher aqua regia concentrations were precipitation yields decreased, ensuring a selective gold recovery across a range of leachate conditions. The disclosed results improve the circularity of gold by providing a new avenue for its simple recycling.publishe

Field tests for control of the mound-building termite Cornitermes cumulans (Kollar, 1832) (Isoptera, Termitidae)

Com a finalidade de combater o cupim de monte Cornitermes cumulans, importante espécie invasora, foram instalados dois campos experimentais. Experimento I: 60 ninhos foram escolhidos e medidos externamente. O ensaio constou de 6 tratamentos com 10 repetições: A) abamectina (50 cm³ CE 1,8%); B) silafluofem (200 cm³ CE 80%); C) silafluofem (400 cm³ CE 80%); D) fipronil (15g G 2%); E) fipronil (20g G 2%); F) clorpirifós (30g G 0,125%). Nos tratamentos A, B, C, as quantidades entre parênteses são da formulação comercial em 100 litros de água. Em D, E, F, são do granulado para cada ninho. Dos líquidos, usou-se um litro de calda por monte. A demolição dos montes deu-se após 103 dias da aplicação. Os melhores resultados foram obtidos com a abamectina e fipronil. Experimento II: Também neste ensaio os cupinzeiros foram 60, abrangendo 6 tratamentos com 10 repetições: A) fipronil (l0g G 2%); B) fipronil (15g G 2%); C) bendiocarbe (20g G 0,1%); D) bendiocarbe (20g G 0,5%); E) imidaclopride (0,15g G 70%); F) imidaclopride (0,30g G 70%). Em A, B, C, D, as quantidades de granulados são por ninho. Em E, F são de granulado dispersível em um litro de água, por ninho. A destruição dos cupinzeiros foi feita 148 e 149 dias após a aplicação. Os melhores resultados foram o fipronil e imidaclopride.Two field tests were carried out to evaluate the performance of several pesticides for the control of the mound termite pest in pastures. Experiment I: 60 mounds were selected and measured outside. There were 6 treatments with 10 replicátions: A) abamectin (50 cm³ 1.8% EC); B) silafluofen (200 cm³ 80% EC); C) silafluofen (400 cm³ 80% EC); D) fipronil (15g 2% G); E) fipronil (20g 2% G); F) chlorpirifos (30g 0.125% G). In A,B,C, the quantities between parenthesis are of the commercial formulation in 100 liters of water. In D,E,F, are of granular insecticides per mound. One liter of the liquids was used per nest. Demolition of the mounds were made 103 days after the application. The most efficient were abamectin and fipronil. Experiment II: Also 60 nests, with 6 treatments and 10 replicátions: A) fipronil (lOg 2% G); B) fipronil (15g 2% G); C) bendiocarb (20g 0.1% G); D) bendiocarh (20g 0.5% G); E) imidacloprid (0.15g 70% G); F) imidacloprid (0.30g 70% G). In A,B,C,D, the quantities of granular insecticides are by nest. In E,F, of dispersible granule in 1 liter of water, by nest. The demolition of the nests was made 148 and 149 days after the application. The most efficient were fipronil and imidacloprid