WO2001038229A2

WO2001038229A2 - A method for cleaning wastewater from petroleum and oil contamination

Info

Publication number: WO2001038229A2
Application number: PCT/IL2000/000788
Authority: WO
Inventors: Simeon Abramovich; Gregori Pipko; Benjamin Doron
Original assignee: Simeon Abramovich; Gregori Pipko; Benjamin Doron
Priority date: 1999-11-29
Filing date: 2000-11-27
Publication date: 2001-05-31
Also published as: WO2001038229A3; IL133181A0; AU1727401A

Abstract

The invention relates to a method for cleaning water surfaces and wastewater from petroleum, petroleum components and petroleum by-products emulsified or dissolved in the wastewater by passing the wastewater through a layer of absorbing particles comprising partly vulcanized rubber, wherein the partially vulcanized rubber, obtained by partial vulcanization, characterized by having a limited swelling capacity of 300-2000 % its own weight when saturated in diesel fuel.

Description

A METHOD FOR CLEANING WASTEWATER FROM PETROLEUM AND OIL CONTAMINATION

FIELD OF THE INVENTION

The present invention relates to a method for cleaning industrial wastewater from contaminants of petroleum, petroleum components and petroleum by-products. Furthermore the present invention generally relates to a method for cleaning water, soil and work surfaces from petroleum, petroleum components and petroleum by-products contamination slicks.

BACKGROUND

The environmental pollution caused by petroleum and its products is one of the main environmental problems facing environmentalists for more than a century. One important aspect of petroleum pollution is of wastewater contamination by soluble petroleum components which pollute groundwater and water reservoirs. Sources for this type of wastewater pollution vary from big plants involved in the petroleum industry, through any kind of petroleum and petroleum products transportation, to small plants, garages and businesses that are using fuel oil and various petroleum based solvents. The contribution of the last, i.e. of small plants and businesses, to water pollution amounts to a significant part of overall water pollution.

The increasing environmental awareness during the last decades has led in many countries to governmental regulations, enforcing standards for maximal admissible concentrations of petroleum and other organic contamination in industrial sewage. These standards become more and more rigid over the years and consequently force the industries to perfect their purifying systems and to develop new technologies and materials for this purpose.

Presently, there are various different processes for sewage purifying based on different absorbents, filters and chemicals. These processes differ from each l other by their affectivity and their pricing. The situation with regard to purifying industrial wastewater is even more complicated because there is no universal process or material with the ability to purify different sewage with very different contaminants. Therefore, several purifying processes have to be used together, including the purifying by biological means. This kind of complex process, which requires expensive equipment and materials, is available only for very large plants, such as big chemical a petroleum manufactures. However, small plants and businesses such as garages, repair workshops, small metal manufacturing industries, refueling and washing stations, varnish and dye industries etc., are not able to build up complicated purifying systems. These small industries and businesses would have, in the best case, a settling tank or a simple gravitation separator. Many simple filters (for example, different types of natural clay, polymer filters) are offered on the market, however these filters suffer from a basic drawback, namely, their low adsorption capacity relatively to the petroleum products which have to be extracted from wastewater. This capacity usually does not exceed 20 - 30% of the absorbent's own weight. Even the widely used absorbent, active carbon, is able to absorb no more than 20% from its own weight. Because of their relatively low adsorption capacity, these adsorbents cannot be used when the concentration of petroleum contaminants exceed 100-150 PPM. Another drawback of existing adsorbents is the complicated recycling process, i.e., the extraction of oil.

Another environmental problem relates to accidental petroleum spills on water, soil surfaces and at workplaces where petroleum-related components are used. Immediate localization and removal of these slicks is vital. A number of materials were developed to treat this problem, however, they are not always successful. Some of said materials have low adsorption capacity (0.5-5 kg of petroleum on 1 kg of adsorbent). Some of said materials cannot be easily removed from water surfaces. Some of them do not sufficiently float, and drive petroleum down to the bottom. Some of these materials cannot be properly used, since they discharge gases when fired and they resist biodegradation. It is the purpose of the present invention to provide a polymeric material with a very high absorbing capacity for petroleum and other non-polar hydrocarbons, for cleaning wastewater from petroleum, petroleum components and petroleum by-products contamination.

It is yet another purpose of the present invention to provide such a material which is cheap, easily prepared, and easily recycled or destroyed without causing environmental hazards.

The first step toward that purpose is to start with a polymer which has a good solubility in hydrocarbons. High solubility of the polymer in hydrocarbons ensures the opposite, i.e., high solubility of hydrocarbons in the polymer and therefore its ability to take up large amounts of hydrocarbons, i.e., high absorption capacity for petroleum. However, upon taking large amounts of oil, most material will lose their structure and will become sticky and dissolved. Therefore, the material must fulfil another requirement, i.e. it must retain its structure when loaded with large amounts of petroleum.

Different rubbers, e.g.., natural rubber, polyisoprene, polybutadiene etc., have high solubility in hydrocarbons and vice versa. It is known that rubber put in oil will swell and eventually will dissolve completely. One of the main reasons for rubbers vulcanization is to prevent their swelling upon contact with oil. Thus, for example, rubber designated for tires undergoes a very high degree of vulcanization.

It is the purpose of the present invention to provide a rubber material which has intermediate features between these two extremes, i.e., swelling till complete dissolvent on the one extreme and complete prevention of oil up-taking on the other extreme. The rubber according to the present invention, is vulcanized to a certain degree such that it has a very high capacity for oil absorbing, up to several times its own weight, while still retaining a rigid structure. Although the main purpose of the present invention is to provide a method for cleaning water from dissolved petroleum, the rubbers of the present invention can be suitable for removing petroleum spoilage as well. In the context of the present invention the terms absorption and adsorption are used without distinction, although the term adsorption usually refers to the physical process that leads to localization of adsorbed molecules on the adsorbent surface and pores, while absorption refers to the diffusion of adsorbed molecules into the adsorbent, a process which leads to the adsorbent's swelling. In the method of the present invention both processes occur. The materials of the present invention selectively adsorb and absorb non-polar hydrocarbons while water pass through them without being adsorbed or absorbed.

SUMMARY OF THE INVENTION

The present invention relates to a method for cleaning industrial wastewater from petroleum, petroleum components and petroleum by-products emulsified or dissolved in said wastewater by passing said wastewater through a layer of absorbing particles, of 1-20 mm size, comprising partially vulcanized rubber obtain by partial vulcanization, wherein said partially vulcanized rubber is characterized by having an absorption capacity of 800-1000% its own weight when saturated in diesel fuel.

The partly-vulcanized rubber particles adsorb selectively the petroleum and petroleum components , thus leaving the water petroleum-free. The rubber according to the present invention is selected from the group consisting of natural rubber, polyisoprene, polybutadiene, ethylene-propylene copolymer, butadiene-natural rubber copolymer butadiene-styrene copolymer and butadiene-styrene carboxilate copolymer. The vulcanization of the rubber is carried out in block, in latex, in organic solvents or preferably in foamed latex. In a preferred embodiment of the present the vulcanization of the rubber is carried out by elemental sulfur at concentration in the range of 0.1-2% of the rubber weight. The rubber can further comprise active and inert fillers, such as soot, silicon dioxide, kaolin, chalk, or crushed particles of recycled rigid rubber, at concentrations of up to 30% of total weight of the rubber composition.

The rubber particles of the present invention can be regenerated for further use by washing with organic solvents, such as light petrol or light alcohols, followed by the removal of said organic solvents by evaporation, or by water steam blowing, or by washing with water in case of alcohol.

DETAILED DESCRIPTION OF THE INVENTION

The aim of the present invention is to create a polymer, which is able to effectively absorb and hold the petroleum and its products. The polymer according to the present invention has to fulfil two basic requirements. It must interact and be compatible with hydrocarbons so that it can dissolve them easily which means that the polymer can be dissolved by the hydrocarbons easily itself. On the other side, complete dissolving of polymer in hydrocarbons creates a sticky solution, that is difficult to separate. So, there must be a limit to the interaction process between polymer and hydrocarbons, such that it stops when a certain degree of swelling is reached. These requirements are opposite to the regular requirements from a polymer with regard to their oil and petrol stability.

The present invention gives a prescription for the preparation of a material which on one hand is able to absorb big quantities of hydrocarbons, suspended or dissolved in water, and on the other hand, holds the integrity of its structure when a specific limit of material's swelling has being reached. Apart from these main demands, the material must also meet the following requirements: - The absorption of the hydrocarbons by the absorbent material has to be fast enough so that the residence time of the polluted wastewater in the absorbent's zone would be reasonable. - The material in its block or plate shape has to be easily broken up and granulated. This property is especially emphasized when dealing with materials of high elasticity.

- The absorbent granules must not stick together also when they stored in a container under a small pressure.

- The absorbent material should have specific gravity lower than 1 so that it floats on water and can be effective on the water surface as well, especially in open settling tanks.

- The absorbent material cannot comprise components that might leak out or washed out and pollute the water.

- The absorbent material after loaded with hydrocarbons must be recycled easily for reuse and/or can be destroyed without creating of harmful waste.

The conditions and extent of vulcanization, according to the present invention, have to provide a rubber with saturated swelling upon absorbing fuel oil not less than 300 -2000 % of its own weight, at room temperature. The saturated swelling is realized during 0.2 - 6.0 hours depending on the size of the vulcanized polymer particles.

The vulcanization process can be carried out in block, in latex, in foamed latex or in organic solvents. The foamed latex must have not less than 80% opened pores.

The term "in block" means the polymer in a form of soft solid, like dough while

"latex" means an aqueous dispersion of the polymer.

Several types of non-polar polymers can be used for achieving the goals of the present invention. In particular, suitable for the present invention are natural rubber, isoprene, butadiene, co-polymers of butadiene with styrene or with natural rubber.

These polymers have a highest affinity to non-polar hydrocarbons, which are basic components of petroleum wastewater industrial polluting. The vulcanization process of the rubber must be carried out under special conditions in order for the final materials to posses the properties as described above.

The high absorption ability of the adsorbent is provided by the correct selection of the vulcanization reagents and vulcanization system and conditions. Most crucial is the quantity of the cross-linking (vulcanization) agent.

In a preferred embodiment of the present invention, the vulcanization agent is an elementary sulfur at a quantity 3-10 times less than is usually used in the industry for rubber vulcanization, or about 0.1-2% of the rubber weight.

Usually the process of swelling of rubber in petroleum products is quite slow, especially with heavy fraction like crude oil. A significant acceleration of the process can be achieved by increasing the contact surface. Vulcanization of foamed latex can be answer. In this case the time getting to maximal swelling may be reduced from 5-8 hours to 2-10 minutes. It was found that by using vulcanizate, the residence time of the wastewater in a column apparatus can be reduced to 3-5 minutes. In addition to the advantage of reducing contact time, this vulcanizate floats on the water surface which makes it appropriate not only for removing dissolved and emulsified petroleum components, but also for cleaning water surface from floating petroleum pollution. It also prevents a bottom pollution of water reservoirs and of water cleaning systems by adsorbent's particles, which are petroleum saturated and settled down.

Proposed material adsorbs petroleum and petroleum-related products from water and soil surfaces not just by swelling but by porosity of material as well. In this case, said material is able to adsorb up to 20 kg of petroleum-related products using 1 kg of the material. The adsorbent saturates completely within one minute.

Adding a certain amount of fillers into the polymers composition provides the crushing ability to the under-structured rubber with the sparse cross-linking net, and prevents the material from collapsing under storage conditions. The fillers can be selected from soot, silicon oxide, delicate crushed clay and crumbed rigid rubber. These fillers increase the rubber's rigidity thus facilitate its easier crushing, and reduce the cost of the finished product.

Polymer adsorbents, made as described, might contain residues of chemical reagents (such as emulsion stabilizers, vulcanization accelerators, activators, fillers etc.) that are added into the latex while foaming and vulcanizing. Some of these residues are soluble in water and might leak from the absorbent material and pollute the water. Therefore, residues of hydrophilic chemical components must be removed from the adsorbent before its use. This can be done by washing with basic water or with hot ethanol, followed by the removal of ethanol residues by evaporation or by water washing. The ethanol can be regenerated for next applications.

The material, which was compounded from small parts with size of 4-10 mm and placed into a column, absorbs the dissolved petroleum products and their emulsions from the polluting water going through the column. Table 1 summarizes the results for wastewater cleaning obtained by several preferred embodiments of the present invention. The initial concentration of the petroleum components in the water was in the range of 200-300 ppm. The absorption does not depend on the initial concentration of the petroleum products in polluted water and it brings it down to less than 5 mg L with after a contact time of 4 to 15 minutes.

The polluted water were passed through a column of 36 mm diameter, filled with 200 mm layer of adsorbent particles, of 3-8 mm size.

The absorbents tested were the following:

- isoprene rubber, vulcanized in a block.

- isoprene rubber, vulcanized in latex.

- Butadiene-styrene rubber (30% styrene), vulcanized in latex - Two samples of natural rubber vulcanized in latex and foamed. Sample 2 is as Sample 1, with optimal valcanization of the rubber, since Sample 1 contains 2% sulfur, while Sample 2 contains 0.8% sulfur.

Recycling the absorbent material is done by the following procedure: The absorbent saturated by petroleum is treated by solvents, such as light petrol or ethanol, at temperature of 80-100° C. After 1 or 2 treatments, depending on the pollution character, the solvents are removed from the absorbent by evaporation or by water steam blowing, or are washed by water in case of ethanol.

After a number of regeneration cycles, when there is a significant decrease in the absorbent absorption capacity, it can be burned in a proper place or in a firebox. The resulting gases are similar to the gases produced by petroleum burning and there are no specific toxic components in them. Another way to destroy the material is to heat it with tar or in heavy fuels to temperature of 350-380° C. At these elevated temperatures the rubber disintegrates and becomes an integral part of the tar or the heavy oil.

Table 1: Results of removing petroleum from water

Claims

1. A method for cleaning water surfaces and wastewater from petroleum, petroleum components and petroleum by-products emulsified or dissolved in said wastewater by passing said wastewater through a layer of absorbing particles comprising partly vulcanized rubber, wherein said partially vulcanized rubber, obtained by partial vulcanization, is characterized by having a limited swelling capacity of 300-2000% its own weight when saturated in diesel fuel.

2. A method according to claim 1 wherein said rubber is selected from the group consisting of natural rubber, polyisoprene, polybutadiene, ethylene-propylene copolymer, butadiene-natural rubber copolymer, butadiene-styrene copolymer and butadiene-styrene carboxilate copolymer.

3. A method according to claim 1 wherein said absorbing particles are of 2-20 mm size.

4. A method according to claim 1 wherein the vulcanization of said rubber is carried out in block, in latex, in foamed latex or in organic solvents.

5. A method according to claim 1 wherein the vulcanization of said rubber is carried out by elemental sulfur at concentration in the range of 0.1-2% of the rubber weight.

6. A method according to claim 1 wherein said rubber further comprises active and inert fillers at concentrations of up to 30% of total weight of the rubber composition.

7. A method according to claim 6 wherein the fillers are selected from the group consisting of soot, silicon dioxide, kaolin, chalk, or crushed particles of recycled rigid rubber.

8. A method according to claim 1 further comprising regeneration of the rubber particles saturated with oil, by washing or squeezing with organic solvents followed by the removal of said organic solvents from said rubber particles and reusing the regenerated rubber for further cleaning of wastewater.

9. A method according to claim 8 wherein said organic solvents are light petrol or light alcohols.

10. A method according to claim 1 wherein an additional liquid product is created that can be used as a fuel, by drying rubber particles saturated with oil, and destroying said rubber products by heating at 300-380°C.