Sulfomethylation of radiata pine kraft lignin and its use as a molybdenite depressant in selective chalcopyrite-molybdenite separation by flotation

Abstract

Sulfomethylation of radiata pine kraft lignin was performed using formaldehyde and sodium sulfite under alkaline conditions to determine its potential as a mineral depressant for the separation of molybdenite and chalcopyrite by froth flotation. Optimal conditions for the sulfomethylation reaction were 20% (w/w) Na2SO3 at 130 °C for 4.2 h, which resulted in lignin with a sulfonate content of 2.2 mmol/g. Microflotation assays showed that the optimized sulfomethylated kraft lignin (OSKL) depressed the molybdenite in flotation by 93% using 200 mg/L OSKL, while only 5% chalcopyrite depression was achieved. The performance of OSKL was compared with those of commercial lignosulfonates, and the OSKL displayed a better ability to separate molybdenite and chalcopyrite, even at lower concentration doses. FTIR and 1H-NMR analyses showed that sulfonic groups were incorporated into the C5 position of the aromatic ring and into the aliphatic chain of the OSKL. The hydroxymethyl content of the OSKL was increased, and most β-O-4′, β-1′ and β-5′ bonds were broken, with the exception of the β-β’ bond. Sulfomethylation gives kraft lignin the chemical characteristics of a wood-based molybdenite depressant, making it an alternative to current reagents used in the chalcopyrite-molybdenite flotation process.

Improved Flotation Separation of Scheelite from Calcite by Sulfomethylated Kraft Lignin

“…Previous reports have revealed that kraft lignin (KL) has the potential to be a good depressant [ 12 ]. This is a promising and renewable material mainly derived from the paper industry [ 13 ].…”

“…This resulted in an increase in its hydrophilicity and electronegativity. Vidal et al sulfomethylated radiata pine kraft lignin and utilized it as a depressant for molybdenite, achieving the successful flotation separation of chalcopyrite and molybdenite [ 12 ]. Additionally, Sun et al indicated that the sulfonic acid groups of calcium lignosulphonate (CLS) interact strongly with the Ca sites on the surface of calcite, chemically adsorbing as Ca−SO 3 .…”

Produção integrada de monossacarídeos e lignosulfonatos a partir de bagaço de cana-de-açúcar

“…A análise de infravermelho (FTIR) do licor negro (Figura 13A) apresentou semelhança ao FTIR de um lignosulfonato comercial (Figura 13B). A banda intensa em 1042 cm -1 pode ser atribuída a ligações S=O e várias bandas de média intensidade entre 800 cm -1 e 400 cm -1 são atribuídas a ligações S-O e C-S dos grupos sulfônicos ligados à lignina (VIDAL et al, 2021).…”

“…Os dados mostram que o teor de carbono aumentou após a ultrafiltração, o que parece estar associado com a remoção expressiva de compostos inorgânicos do licor. O teor de carbono estimado para os lignosulfonatos purificados foi de 45% para ambas as amostras, sendo condizente ao teor encontrado na literatura para lignosulfonatos (GUTIERREZ et al, 2020;VIDAL et al, 2021).…”

“…Outra banda característica de lignosulfonatos é encontrada em 1042 cm -1 , sendo atribuída a vibração de alongamento das ligações S=O, indicando que o grupamento sulfônico está presente na molécula e a banda em 1042 cm -1 se intensifica quando o licor é purificado (LI et al, 2018;DEMUNER et al, 2021). Outras bandas de baixa intensidade de 800 cm -1 a 400 cm -1 são atribuídas a ligações SO e CS de grupos sulfônicos ligados a lignina (LI et al, 2018;VIDAL et al, 2021). licor negro e do licor de ressulfonação do ponto ótimo apresentaram banda típica em 280 nm atribuída a anéis aromáticos substituídos por grupos hidroxila (-OH) e metoxila (-OCH3) de estruturas de lignina.…”