The structure-property relationship of p-alkoxyl benzohydroxamic acids towards wolframite flotation: Theoretical and experimental investigations

Electron donating ability and hydrophobicity are of the two aspects related to flotation performance of a collector. To solve the insufficient collecting power of benzohydroxamic acid (BHA) in tungsten ores flotation, its derivatives p-alkoxyl benzohydroxamic acids (AOBHAs) were designed as the advanced wolframite collectors. The computational results inferred that compared with BHA, the p-π conjugation between the alkoxyl oxygen and phenyl ring enhanced the electron donating ability of AOBHAs. Meanwhile, AOBHAs exhibited higher hydrophobicity which increased with expanding the carbon chain length of alkoxyl. On this basis, MOBHA (p-methoxy BHA), EOBHA (p-ethoxyl BHA), POBHA (p-propoxyl BHA) and BOBHA (p-butoxyl BHA) were synthesized, and their flotation response towards wolframite was explored through adsorption, zeta(ζ)-potential and contact angle measurements as well as micro-flotation tests. The findings indicated that the adsorption capacities, rangeability of ζ-potential and hydrophobization to wolframite followed the sequence of BOBHA > POBHA > EOBHA > MOBHA > BHA. After pre-activation with 1.0 × 10−4 mol/L lead nitrate, the flotation recovery of wolframite reached about 12.6%, 87.6%, 93.1%, 93.4% and 95.2% for 2.0 × 10−5 mol/L BHA, MOBHA, EOBHA, POBHA and BOBHA, respectively. The experimental findings well supported the molecular design hypothesis.