Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/28—Treatment of water, waste water, or sewage by sorption
  • C02F1/286—Treatment of water, waste water, or sewage by sorption using natural organic sorbents or derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F9/00—Multistage treatment of water, waste water or sewage
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/16—Regeneration of sorbents, filters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
  • Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy

Definitions

• the present invention concerns a process and corresponding equipment, to remove and recover heavy metals from liquid effluents.
• the process includes two main stages. In the first stage, called biosorption, the heavy metals contaminating the effluent to be treated are adsorbed on the biomass: dried and ground grape stalks. This stage is carried out in a set of continuous mechanically stirred reactors (14), (15), (16), individually connected to continuous settlers (17), (18), (19). In the second stage the biomass is regenerated using a suitable eluent. This stage is carried out in a filter press with membrane plates (30) and control valves of the eluent flow (3) . From this integrated process results the removal of heavy metals from the effluent and their recovery as a concentrated aqueous solution. This solution can be effectively and profitably fed to a metals recovery hydrometallurgical process.
• the process proposed in the present invention allows to remove heavy metals in solution, that is, metallic ions of the elements from the d and f blocks of the periodic table, by biosorption, flocculation , sedimentation, filtration and elution.
• the effluent was contacted countercurrently with the dried and ground grape stalks, called biomass in this patent.
• biomass was contacted countercurrently with the dried and ground grape stalks, called biomass in this patent.
• the biomass loaded with heavy metals was filtered and immobilized in the filtration cakes of a filter press with membrane plates (30) which have control valves of the eluent flow (3) .
• Elution was carried out with an eluent of high ionic strength passing through the cakes sequentially.
• the elution stage allows regenerating the biomass for a new cycle of biosorption, flocculation, sedimentation, filtration and elution.
• An eluate with high heavy metals concentration is obtained, that can be effectively fed to a hydrometallurgical process of liquid-liquid extraction, cementation, chemical precipitation, membrane separation or electrolysis .
• the present invention applies to the mining sector namely to the treatment of acid effluents from abandoned mines and to the treatment of water coming from mining tailings dams, to the metal surface treatment industries sector and, on the whole, to the treatment of watercourses contaminated with heavy metals.
• Biosorption is defined as the capacity of biological materials (biomass) to adsorb metallic ions of the elements from the d and f blocks of the periodic table from aqueous effluents.
• Volesky et al. (1988, Pat. No. 4,769,223) developed a method for the biosorption of gold using seaweed (Sargassum genus) stabilized by a wide variety of natural and synthetic polymers.
• Jeffers et al. (1994, U.S. Pat. No. 5,279,745) developed the granular encapsulation in polysulfone polymers to immobilize absorbents, which constitutes the basis of the BIO- FIX system developed by the United States Bureau of Mines.
• Butter et al . presents a biosorption and elution system, using a suspension of Penicillium chrysogenum as biomass.
• the biosorption was carried out in a tubular reactor and the elution in a Niitsche filter.
• Matis et al. (2003) carries out the biosorption of heavy metals using the Streptoverticillium cinnamoneum and Penicillium chrysogenum non-viable microorganisms as biomass.
• the process proposed in the present invention allows treating, by biosorption, high flow rates of effluents with a low concentration of metallic contaminants.
• a biosorption process a reactional systems where the biomass is in homogeneous suspension is the most suitable process.
• the loaded biomass with heavy metals was immobilized in the filtration cakes obtained in the filter press with membrane plates (30) , characterized by having control valves of the eluent flow (3) .
• the biomass immobilization is a consequence of the filtration operation.
• the membrane filter plates developed allows for a sequential elution of the filter cakes, i.e. the eluent coming out of a given upstream filter cake enters directly in the next cake, this process being repeated until the last filter cake. This procedure, from the standpoint of view of elution, transforms the sequence of several filter cakes in a single packed column.
• the present invention concerns a process and corresponding equipment, to remove and recover heavy metals from liquid effluents.
• the process includes two main stages. In the first stage, called biosorption, the heavy metals contaminating the effluent to be treated are adsorbed on the biomass: dried and ground grape stalks. This stage is carried out in a set of continuous mechanically stirred reactors (14), (15), (16), individually connected to continuous settlers (17), (18), (19). In the second stage the biomass is regenerated using a suitable eluent. This stage is carried out in a filter press with membrane plates (30) and control valves of the eluent flow (3) . From this integrated process results the removal of heavy metals from the effluent and their recovery as a concentrated aqueous solution. This solution can be effectively and profitably fed to a metals recovery hydrometallurgical process.
• the process proposed in the present invention consists in contacting the liquid effluent contaminated with heavy metals with dried and ground grape stalks.
• the particle size distribution of the ground grape stalks is characterized by a Sauter mean diameter in the range between 5 mm and 250 mm.
• the contact is carried out in countercurrent and in a set of continuous mechanically stirred reactors (14), (15), (16) and settlers (17), (18), (19).
• a suspension of dried and ground grape stalks with 6 a 15% (w/w) of solids is obtained; this suspension is sent to a filter press with membrane plates (30) .
• a filtration and compression of the filter cakes is performed in order to obtain a filter cake with 30%-70% of solids.
• the elution of the cake was carried out with an eluent of high ionic strength as example: solution of NaCl 4 molar or a2S0 4 1 molar, which must contain a complexing agent for heavy metal such as tri-sodium citrate dehydrate.
• Elution is carried out in the filter press with membrane plates (30) with the eluent passing sequentially through the filter cakes.
• the entrance of the eluent into the filter press with membrane plates (30) is accomplished through the flow channels of the filtrate.
• the elution is called sequential because the eluent passes through the filter cakes sequentially, i.e., the eluent that leaves the first filter cake enters into the second cake and this procedure is repeated until the last filter cake is reached.
• the passive transport mode means that the driving force for the transport of the eluent is the hydraulic gradient of pressure between entrance and exit, as result of the specific resistance of the filter cake, which is overcome by the feed pump.
• the active transport mode the eluent passes through the cakes forced by inflating sequentially the membrane of each membrane filter plate. The active transport of the eluent allows working at low eluent feeding pressures because the pressure drop is only related to the specific resistance of a single cake. Thus, the leakage at the junction of two consecutives filtration plates is minimized and also the formation of preferential flow channels is avoided.
• the sequential elution with active transport allows concentrating in a reduced volume of eluent the metals that were adsorbed by the biomass in the biosorption stage.
• the sequential passage of the eluent through the cake is only possible due to the innovative design of the membrane plates with control valves of the eluent flow (3) in the main flow channels.
• the main channels for the flow of the filtrate of each plate are also the feed channels in the elution stage, those being the orifices located in the corners of the filtration plates.
• each main flow channel/feed channel is controlled by a control valve of the eluent flow (3) which is designated herein with the abbreviation VCFE.
• Figure 1 presents a diagram related to the sequential elution of filter cakes in order to simplify the exposition of the elution process.
• the central channel is filled with biomass, which hinders the passage of eluent through this channel.
• the technology developed in the present invention allows removing toxic from wastewater and concentrating the same heavy metals 8 to 50 times into a new aqueous phase with reduced volume at low cost, since energy is only required for pumping the biomass suspensions through several pieces of equipment that constitutes the invention.
• the washing of the cakes can be performed at the filter press with membrane plates (30) by sequentially passing the wash water, from the tank (11), through the filter cake. After washing, the filter press with membrane plates (30) is opened and the biomass unloaded in the receiving tank (13) .
• This tank continuously feeds the conveyor screw or biomass pneumatic conveyor (29) that continuously recirculates the biomass to the continuous mechanically stirred reactor (16) .
• the high concentration of metals in the eluate at the exit of the filter press with membrane plates (30) allows them to be efficiently recovered by chemical precipitation, electrochemical precipitation, solvent extraction or by electrolysis. This operation of final recovery of the metal allows regenerating the eluent to be used again for the biosorption and elution process.
• the process and equipment proposed in this invention enables the removal and recovery of heavy metals from wastewater using an integrated unit of biosorption, sedimentation flocculation, filtration and elution composed by a battery of continuous mechanically stirred reactors (14), (15), (16) and continuous settlers (17), (18), (19) and a filter press with membrane plates (30) characterized by having control valves of the eluent flow (3) in closed and open positions.
• the process comprises four main stages:
• step c) Filtration of the suspension obtained in step a) in a filter press with membrane plates (30) having control valves of the eluent flow (3) in the open position, forming filter cakes with a solids concentration between 30 and 70 % (w/w) ; d) Elution of the metals existing in the dried ground grape stalks, immobilized in the form of filter cakes through the eluent active or passive transport mode by passing the eluent sequentially in the filter cake using the head membrane filter plate (6), the inner membrane filter plates (7), the end membrane filter plate (5) and the control valves of the eluent flow (3) in the closed and open positions.
• biomass used for the biosorption of the heavy metals There are several factors that determine the choice of biomass which are listed below:
• the biomass must have high affinity and high maximum saturation capacity towards the targeted heavy metals.
• the filter cakes should be porous in order to allow the eluent flow without excessive losses of hydraulic load.
• the heavy metals should be reversibly bonded to the biomass, allowing the regeneration of the biomass by using appropriate eluents, in order to obtain concentrated eluates with the targeted heavy metals .
• the fresh grape stalks are obtained from wineries, washed and dried by exposure to direct sunlight or in greenhouses, and then ground using hammers or knives mills in order to obtain the appropriate particle size distribution.
• the fresh grape stalks are stored in the receiving tank (13) that also receives the filter cakes with 65% to 75% dried solids, obtained after cake elution and washing.
• the grape stalks from the receiving tank (13) are continuously fed using an auger conveyor or biomass pneumatic conveyor (29) to the last continuous mechanically stirred reactor (16) of the battery of the reactional system comprised by the continuous mechanically stirred reactors (14), (15), (16) and by the continuous settlers (17) , (18) and (19) .
• the aqueous phase from the continuous settler (18) enters in the continuous mechanical stirring reactor (16) .
• the suspension is forwarded to the continuous settler (19) , where a solid liquid separation is performed.
• the treated effluent overflows at the top of the continuous settler (19) and at the bottom of the same continuous settler (19) a suspension leaves with a solids concentration ranging from 8 to 15%, which it is transported by a positive displacement pump (22) to the continuous mechanically stirred reactor (15) .
• This same continuous mechanical stirred reactor (15) receives the aqueous phase from the continuous settler (17).
• the process just described above is a countercurrent process and can be repeated for an arbitrary number of continuous mechanical stirred reactors (14), (15), (16) and continuous settlers (17), (18) and (19) .
• the number of reactors is a function of the composition and concentration of heavy metals present in the effluent as well as of the required rate of removal of heavy metals.
• the number of reactors in the battery or the concentration of biomass in the reactor can be increased.
• the latter alternative causes dilution of the heavy metals in the biomass and hinders the final concentration factor.
• Figure 2 only shows a battery with three reactors, for the purposes of mere illustration without binding the invention to a specific number of reactors in the battery.
• the elution of the existing heavy metals in the dried and ground grape stalks is held in active or passive sequentially mode inside the filter press with membrane plates (30) .
• the eluent is stored in the feed tank (9) of eluent and is introduced into the filter chambers of the filter press with membrane plates (30) using a centrifugal pump (26) .
• the centrifugal pump (26) is used for feeding the. filter press with membrane plates (30) with the eluent and also with the cake washing water.
• the eluent with high metal concentrations, 8 to 50 times higher than those in the initial effluent is stored in the receiving tank (10) .
• Tank (11) is the cake washing water
• tank (12) is the cake washing water receiving tank.
• Figure 1 shows an exploded view of three filtration plates and two filter cakes and exemplifies the sequential elution of the filter cakes with the input of fresh eluent (1), output of eluent loaded with heavy metals (2), control valves of the eluent flow (3), the end membrane filter plate (5), the head membrane filter plate (6), and the inner membrane filter plate (7) .
• the process may take place with an arbitrary number of inner membrane filter plates (7) .
• Figure (1) only shows one inner membrane filter plate (7) for mere illustrative purpose, without binding the invention to a specific number of inner membrane filter plates (7).
• the central channel is filled with solids with high resistance to the passage of the eluent .
• FIG. 2 shows the diagram of the process, with the tank (8) of the effluent containing heavy metals, the eluent feeding tank (9) to the press filter with membrane plates (30), the receiving tank (10) containing the eluate concentrated with heavy metals, the tank (11) of fresh water for cake washing, the receiving tank (12) of cake washing water, receiving tank (13) of filtration cakes after elution and washing, continuous mechanically stirred reactors (14), (15) and (16), forming a battery of three reactors, continuous settlers (17), (18) and (19), effluent feeding centrifugal pump (20) to the continuous mechanically stirred reactors (14), (15) and (16), positive displacement pumps (21), (22) for transport of the suspension between the different continuous mechanically stirred reactors (14), (15) and (16) and continuous settlers (17), (18), (19), progressive displacement pump (23) for feeding the filter press with membrane plates (30), centrifugal pumps (24), (25) for transport of the aqueous phase between the different continuous mechanically stirred reactors (14), (15)
• Example 1 Removal/recovery of copper from a waste water containing 10 ppm of copper in aqueous solution.
• Each inner membrane filter plate (7) has a surface filter area of 40x40 cm 2 allowing the formation of cakes 4 cm thick.
• Three inner membrane filter plates (7) were used, plus the head membrane filter plate (6) and the end membrane filter plate (5), which formed altogether four filter chambers. Elution was performed using 200 L of eluent made with the following composition: 1 Molar solution of Na 2 S0 4 and 0.1 Molar tri-sodium citrate dehydrate.
• the control valves of the eluent flow (3) were closed to allow sequential elution as described earlier.
• the eluent passive mode of transport was used, with an inlet pressure of 300 mbar.
• the feeding rate was 30L/h. An average concentration of 280 ppm was achieved with an elution rate of 95%.
• the cake washing was conducted with 20 L of water. The filter cakes were recirculated to the battery of two continuous mechanically stirred reactors (14) and (15). Given the initial concentration of the effluent to treat the average concentration of Cu 2+ obtained in the eluate represents a concentration factor of 28 times.
• Example 2 Removal/recovery of copper from a waste water containing 50 ppm of copper in aqueous solution.
• Each inner membrane filter plate (7) has a surface area of 40x40 cm 2 allowing the formation of cakes 4 cm thick.
• Seven inner membrane filter plates (7) plus the head membrane filter plate (6) and an end membrane filter plate (5) were used forming eight filter chambers.
• Elution was performed with 250 L of eluent with the following composition: 1 Molar solution of Na 2 SC>4 and 0.1 Molar tri-sodium citrate dehydrate.
• the control valves of the eluent flow (3) were closed in order to allow sequential elution as described earlier. Active mode of transport of the eluent was used.

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• Life Sciences & Earth Sciences (AREA)
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• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Processing Of Solid Wastes (AREA)

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Citations (9)

• 2013
  • 2013-09-11 PT PT10715113A patent/PT107151B/pt active IP Right Grant
• 2014
  • 2014-09-09 WO PCT/PT2014/000060 patent/WO2015038021A1/en active Application Filing

Patent Citations (9)

Non-Patent Citations (5)

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