Adsorption of Commercial Lignosulphonates On Fractionated Bentonitic Clays
Authors: Fertl Walter , Jessen F.W. 
Published: March 2010

Adsorption of Q-Broxin, a Fee Cr-Lignosulphonate, and Unical, a Cr-Lignosulphonate, on fractioned-sized natural and monoionic clay particles has been studied. Adsorption takes place predominantly on the broken edges of the clay particles.

The adsorbed lignosulphonate molecules caused no change in either the Na.+ or Ca++ replacement at low electrolyte concentrations. However, when the concentration was increased a decrease of 8 to 15 per cent in total cation replacement was noted.

INTRODUCTION AND STATEMENT OF PROBLEM

IN THE DEVELOPMENT OF DRILLING FLUIDS, various lignosulphonates have been employed successfully for several years in rheology control for both fresh-water-and salt-water-base muds and for filtration control of weighted muds.

The purpose of this investigation was to study the adsorption behaviour of Q-Broxin. a Fe-Cr-Lignosulphonate, and Unical, a Cr-Lignosulphonate, on various clay suspensions and to observe the effect of the adsorption on cationic exchange with electrolyte concentration under equilibrium conditions.

EXPERIMENTAL TECHNIQUES

Wyoming bentonite fractions obtained by Mungan(1) were used in this study. A quantity of 500 mg of each clay fraction ranging in size from 1 to .05 micron, which had been stored dry in an air-conditioned room at 74–77 °F. were mixed with 100 ml of demineralized water. These hydrated stock suspensions were allowed to stand for five days and were stirred several times a day. Using a batch-treatment technique and proper exchange resins, each fraction was converted to monoionic systems of both the Na+ and Ca2+ form. Completeness of the conversion was checked by titration, using specific glass electrodes, and by X-ray analysis.

The Fe-Cr-Lignosulphonate (Q-Broxin) and the Cr Lignosulphonate (Unical) were both commercial-grade materials in common use in treating oil-well drilling fluids.

Apparatus and Equipment Used

A Beckman Sodium Ion Glass Electrode(2) was used to measure the Na'" concentration; the Ca2+ concentration was monitored by the Calcium Activity Electrode, l\!Iodcl 92–20(3). A Beckman Calomel Electrode was used as a reference electrode. The sensitivity and detection limits of these electrodes have been described previously by Fertl and Jessen(4).

For both mono- and divalent electrodes, calibration curves were established by plotting known normalities of the ion to be determined against the potential, in mv, obtained from an electrometer output. After each measurement, the electrodes were rinsed and dried before immersing them into a different sample. As response to H+ can interfere with specific ions being measured, the operable range, with a pH of 6.8–7.5, was monitored. The electrodes were checked against the calibration curves intermittently during the experiments and, when necessary, the base line of the calibration curve was reset with one of the calibrating solutions. Also, several blank tests were run to determine the effect of the lignosulphonates on the calibration of the specific ion electrodes. No noticeable effect was observed.

A wide-band D.C. amplifier. IHodel 603 from Keithley Instruments Incorporated ‘5J, with nine,’ oltagerang-es from 2.5 to 1000 mv full scale, was used. This amplifier has an extremely high input impedance and high voltage and current sensitivity.