In this survey, Bacillus subtilis biomodified PSAC, was utilizing as a biosorbent for the remotion of lead from aqueous solution. The biomodified PSAC was characterized for its surface country, point of zero charge and acidic surface group concentration. Batch surface assimilation experiments were carried out to analyze the effects of different initial metal ions concentration ( from 30 mg/L to 300 mg/L ) and initial solution pH ( from pH 3 to pH 6 ) . Percentage consumption of biomodified PSAC was found to diminish with an addition in initial lead concentration. This was due to restriction of the adsorbent mass where the binding site of adsorbent or solute ratio was smaller. The sorption capacity of biomodified PSAC increased with increasing in initial lead concentration and pH. This biosorbent showed high surface assimilation capacity for lead ions particularly at pH 6 with an ultimate consumption of 71.43 mg/g due to the lower competition between protons and lead ions at higher pH. Biosorption of lead by biomodified PSAC was best described by the Langmuir surface assimilation isotherm theoretical account, in which the procedure can be concluded as monolayer sorption procedure of lead ions onto biomodified PSAC. The findings of this probe suggest that biomodified PSAC can be used as an effectual adsorbent for the remotion of lead from effluent.
There is an increasing concern about heavy metal pollution in Malaysia due to the industrial and agricultural development, increasing life criterions and broad domains of human activities. Heavy metal such as lead ( Pb ) , Cu ( Cu ) , nickel ( Ni ) , Cr ( Cr ) , Cd ( Cd ) , quicksilver ( Ag ) , aluminium ( Al ) and Zn ( Zn ) are normally found to be disposed to the drainage system and flux directly to the river. Heavy metal ions are toxic, non-biodegradable and extremely carcinogenic. In order to take heavy metal ions from effluent, many researches had been look intoing effectual H2O intervention engineerings such as surface assimilation, chemical precipitation, rearward osmosis, solvent extraction and ion exchange. Among the assorted engineerings available, surface assimilation by utilizing activated C is the most popular and has been widely used for the remotion of pollutants from effluent in footings of the initial cost, simpleness of design, easiness of operation and insensibility to toxic substances ( Meshko, Markovska, Mincheva and Rodrigues, 2001 ) . However, production and regeneration of commercial activated C is still expensive. Therefore, research attending has been focused on the industrial and agricultural wastes based activated Cs that are lower in cost. The transition of natural organic wastes into environmentally-friendly porous stuffs is a technological option to their disposal.
In the twelvemonth of 2006, Malaysia was the largest manufacturer and exporter of palm oil in the universe ( Sumathi et al. , 2008 ) . With such a immense sum of palm oil production, the measure of oil thenar biomass produced is besides high. In Malaysia, around 2 million metric tons of thenar shell is generated yearly ( Chan, 1999 ) . Therefore, application of thenar shell activated C as adsorptive serves a dual intent by change overing unwanted and excess agricultural waste to utile, valuable stuff and provides an efficient adsorptive stuff for the remotion of pollutants from H2O. Recently, several research workers have studied heavy metals removal from aqueous solution utilizing PSAC ( Issabaveya, 2005 ; Gueu, Yao, Adouby and Ado, 2006 ; Shilpi, Suparna and Padmaja, 2008 ; Chun, Mohamed and Wan Mohd Ashri, 2008 ) .The researches indicated this stuff exhibited high surface assimilation capacity towards heavy metals. However, merely few surveies focused to the bacteriums consequence on heavy metals removal in farinaceous activated C. Rivera-Utrilla, et Al. ( 2001 ) investigated surface assimilation belongingss of Escherichia coli biomodification activated C toward lead aqueous solution. Kim, Chang, Jeong and Song ( 2010 ) studied capacity of iron-impregnated activated C to take arsenous anhydride from aqueous solution in the presence of bacteriums. The information on the biomodification of PSAC with bacteriums is scarce.
The species used in our experiments is Bacillus subtilis, a gm positive aerophilic species normally found in effluent system. Most of the bacteriums are negatively charged because the anionic group nowadays within the cell wall ( Sukdeb, Joardar and Joon, 2006 ) . Therefore, alteration of the surface potency of PSAC to be positive is expected better bacteriums surface assimilation efficiency. Bacterial cell walls contain a assortment of surface organic functional groups, including amino, carboxylic, hydroxyl and phosphate sites ( Jeremy, Christopher, Nathan and Thomas, 1997 ) . B. subtilis is bacillar and typically 5.0 Aµm long and1.0 Aµm broad. Kim et Al. ( 2010 ) indicated that the bacterial fond regard could be restricted largely to the external surfaces of farinaceous activated C due to their smaller size relation to bacterial sizes. The waste micro-organisms had been used as alternate adsorbent for the intervention of heavy metal incorporating effluent. Bacteria attach on PSAC will alter the belongingss and construction of adsorbent, in bend consequence the surface assimilation belongingss of adsorbent. It was show that Bacillus sp. efficaciously cleans 21mg/g of Cu ions ( Lo et al. , 2003 ) and take 68.5 mg/g of quicksilver ( Xue et al. , 2010 )
In this research undertaking, a survey has been carried out to analyze the surface assimilation capacity of untreated and pretreatment of PSAC with Bacillus subtilis toward Pb ( II ) , Cd ( II ) , Zn ( II ) and Cu ( II ) nowadays in aqueous solution. Both of the adsorbent were characterized by different physio-chemical methods. The consequence of initial adsorbable concentration, solution pH and contact clip on the surface assimilation of heavy metals were besides evaluated.
MATERIALS AND METHODS
Preparation of Adsorbate. Lead ( Pb ) , Zinc ( Zn ) , Cadmium ( Cd ) and Copper ( Cu ) were selected as the key sorbates in this survey. 0.15 M of NaNO3 from Merck was used as the background electrolyte while 0.1 M of Pb ( NO3 ) 2, Zn ( NO3 ) 2, Cd ( NO3 ) 2, and Cu ( NO3 ) 2 were used as the heavy metals ions beginning. Stock solutions of the four heavy metal solution with concentration of 0.1 M were prepared by fade outing with background solution. The trial solutions were prepared by thining the stock solution to the desired heavy metals concentrations.
Preparation of Adsorbent. The commercial farinaceous thenar shell based activated C ( PSAC ) was provided by a local maker “ Bravo Green ” Sdn Bhd in Kuching, Sarawak, Malaysia. The PSAC was produced by physical activation procedure with steam as the energizing agent. It was crushed and sieved to bring forth fix atoms of sizes runing from 0.6 to 1.2 millimeter for used throughout the experiment. Bacillus subtilis, gram positive bacteriums that obtained from Universiti Tunku Abdul Rahman ( UTAR ) was used to biomodified PSAC in this survey. A sum of 40 milliliter of bacteriums cell suspension was added to a 50 milliliter extractor tubing which incorporating 1.2 g of PSAC. The contents of the extractor tubing were stirred with a whirl sociable for 2 min and the tubing was so placed in an orbital shaker. The tubings were maintained at 27A°C with little agitation ( 45rpm ) for 24-h ( Rivera-Utrilla, et Ac, 2001 ) . After that, the biomodified PSAC was filtered and washed gently with unfertile deionizer H2O. It was dried in brooder ( 80A°C ) overnight and so cooled down in desiccators.
Adsorption Studies. In this survey, the surface assimilation experiments were carried out in an orbital shaker ( LabTech ) at a changeless velocity of 220 revolutions per minute at 27A°C utilizing 250 mL conelike flask. The flasks contain 250 milligram of adsorbent in 100 milliliters heavy metal solution with concentration scope from 30 to 300 mg/L were placed in the shaker for 24-h unless otherwise stated. At the terminal of the experiments, the adsorbent was removed by filtration through ”Double-ring ” No. 102 filter paper ( Xinhua Papermaking Ltd Co. , Hangzhou, China ) . The staying heavy metal concentrations in the solution were estimated by utilizing Optima 7000 DV Inductively Coupled Plasma-Optical Emission Spectrometer ( ICP-OES ) ( Perkin Elmer, USA ) harmonizing to standard processs. All the experiments were carried out in extras and the consequences are presented in the per centum consumption and sorption capacity.
However, positively-charged aminoalkane groups ( NH+3 ) are besides present on bacterial surfaces, [ 44 ] so anionic species can adsorb to bacteria via electrostatic attractive force or H bonding. [ 43 ] . At a reaction clip of 12 hour, the per centum of As ( III ) remotion in the presence of bacterium was 61.3 % , which was somewhat lower than that in the absence of bacteriums ( 65.2 % ) . The per centum of As ( V ) remotion in the presence of bacteriums ( 64.4 % ) was besides somewhat lower than that in the absence of bacteriums ( 69.9 % ) . At 72 hour, the per centum of As ( III ) remotion in the presence of bacteriawas 61.0 % , while it was 61.5 % in the absence of bacteriums. The per centums of As ( V ) remotion in the presence and absence of bacteriums were 61.0 % and 62.5 % , severally. This indicated that the influence of bacteriums on arsenic remotion in Fe-GAC was non high in our experimental conditions.