Surface speciation of phosphate on goethite as seen by InfraRed Surface Titrations (IRST)

ZANINI, GRACIELA P.; AVENA, MARCELO J.; ARROYAVE, JEISON MANUEL; AVENA, MARCELO J.; ARROYAVE, JEISON MANUEL; PUCCIA, VIRGINIA; PUCCIA, VIRGINIA; ZANINI, GRACIELA P.

SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY.

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2018 vol. 199 p. 57 - 64

1386-1425

Pho sp hat e adsorpti on a t the m eta l oxide -w ate r interfa ce ha s bee n intensely s tu d ied, and the sy st em ph o spha teg oethite in aqueous me di a i s nor m ally u se d a s a mo de l system with a bun dant inf orm atio n regardin g ads orptio ndes orption u nder v er y di f fe rent c onditi ons. I n spite of t his, th ere is stil l dis cu ssion on wh ether th e mai n in ners phere s urface c om ple xes t ha t p ho sp hat e fo rms o n goethite are mo nodentate or biden tate. A ne w sp ectro sc opicte ch nique, Inf raRed S urf ac e Titrat ion (I RST), is prese nt ed here a nd used to sys tematically explor e t he su rface sp ec iati on of pho spha te on go ethite i n the p H ran g e 4 .5?9.5 at di ffere nt surface cove rage s. IRS T enab le d to co ns tructdi stri buti on c u rv es of su rface sp eci es a nd distribution curve s of dis so lved phos pha te sp eci es. In co mbi na ti on w ithth e CD-MUSIC su rf ac e c om ple xation m ode l it was possible t o co nclude that su rface co mplexes ar e m o nodentate .Very acc urat e d istri bution c urves w ere ob tained, sh owing a cr oss ing po int at pH 5.5 at a s u rf ace c o verage o f 2. 0μm o l m−2 , w ith a m on o nucl e ar m on opro t o na t ed s pecie s pr ed om in ati ng a t p H N 5 .5 a nd a mo n o n uc l ea rdi protonat ed s pec i es p reva ili ng at pH b 5.5. On t he co n trary, a t t h e low sur face cov erage of 0.7 μm o l m−2 thereis no cr o ssing poi nt, wi th t he mononucle ar m ono protonated spe ci es p re vailin g at all p H. IRST c an becom e a po werful t echniqu e to i nv e stig ate s truc ture, prop ertie s an d r eacti ons of any I R-ac tiv e s u rf ace co mplex at t he s o lid -wat er int erface