Organo-Clay/Anthracite Filtration for Oil Removal
Authors: Moazed H. , Viraraghavan T. 
Published: March 2010

A bentonite organo-clay/anthracite mixture in the granular form (EC-100) was used in filtration (column) studies in treating four representative oil-in-water emulsions. The oil-in-water emulsions used were as follows: Standard Mineral Oil (SMO); Kutwell 45 (KUT) and Valcool (VAL), two cutting oils; and Refinery Effluent (RE) from the Co-operative Oil Refinery, Regina, Saskatchewan. The concentrations of oil in the oily waters varied from 8.3 to 69.3 mg/L. Eight-hour column studies were conducted in a 19 mm ID, 450 mm/1200 mm long cast acrylic pipe with an organo-clay/anthracite depth of 300 mm/1,000 mm. The SMO, KUT, and VAL oil-in-water emulsions were pumped into the column at four flow rates of 3, 6, 9, and 12 mL/min (0.3, 0.5, 0.8, and 1.0 gpm/ft2, respectively). Column breakthrough studies were conducted in a 19 mm ID, 1,200 mm long cast acrylic pipe using the organo-clay/anthracite mixture of 1,000 mm depth. The study was conducted for SMO, KUT, VAL and RE oil-in-water emulsions with a flow rate of 12 mL/mim (1 gpm/ft2). The eight-hour column tests with 300 mm bed depth and all oil-in-water emulsions indicated that generally, the oil removal efficiencies decreased with an increase in flow rate. The percentage reduction in oil removal efficiency was 29 and 37 for SMO, 51 and 59 for KUT, and 9 and 57 for VAL when the flow rate was increased from 3 mL/min to 6 and 9 mL/min, respectively. The results of the eight-hour experiments with a 1,000 mm depth of organo-clay/anthracite bed and with a flow rate of 12 mL/min showed that oil removal efficiency for SMO, KUT, and VAL varied between 65 and 70﹪. In the ase of RE, which is a treated and highly stable emulsion, the oil removal efficiency was found to be 99.5﹪. The results from the breakthrough studies clearly indicated that the Thomas equation provides a reasonable fit of the data. The oil-sorption capacities (x/m) based on a mass balance analysis were found to be 0.0036, 0.0019, 0.0015, and 0.0018 for SMO, KUT, VAL, and RE, respectively. The analysis of the breakthrough data using the Thomas model resulted in similar values of x/m. The results also showed that uptake of oil by an organo-clay/anthracite mixture can well be described by a simple equation involving time, such as Weber and Morris model.

Introduction

Organo-clay can be described as modified bentonite. The modification process becomes complete by exchanging the inorganic cations (sodium and calcium) present on the surfaces and interlayer spaces of clays by the nitrogen end of a Quaternary amine, and, thus, changing the hydrophilic nature of clays to organophilic(1, 2).

As a result, organo-clays become excellent sorbents for hydrophobic organics such as oil(3). An advantage of organo-clay compared to other sorbents is that it can selectively remove organic pollutants from contaminated waters.

The sorptive nature of bentonite organo-clay for some organic pollutants has been extensively studied(4-8). However, the effectiveness of organo-clay/anthracite mixture as a filter in the removal of oil from water has not been studied extensively.