**Exhibit 2.2**

**AMENDMENT TO**

**MEMBERSHIP INTEREST PURCHASE AGREEMENT**

This Amendment to Membership Interest Purchase Agreement (this “**Amendment**”), is dated as of July 8, 2015, by andamong Rex Energy Corporation, a Delaware corporation (“**Rex**”) and Sand Hills Management, LLC, a Pennsylvania limited liability company (“**Sand Hills**,” and, together with Rex, collectively, the“**Sellers**”), and American Industrial Water, LLC, an Ohio limited liability company (“**Purchaser**”, and, together with Sellers, the “**Parties**”). 

**RECITALS**

WHEREAS, theParties have previously entered into that certain Membership Interest Purchase Agreement, dated as of June 18, 2015, (the “**Purchase Agreement**”), pursuant to which Sellers desire to sell, and Purchaser agreed to purchase,the Shares (as defined in the Purchase Agreement); and 

WHEREAS, the Parties now wish to amend the Purchase Agreement pursuant to theterms hereof. 

NOW, THEREFORE, in consideration of the premises and of the mutual promises, representations, warranties, covenants,conditions, and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the Parties agree as follows: 

ARTICLE 1 

DEFINITIONS 

**1.1 Definitions**. Capitalized terms used but not otherwise defined herein shall have the meanings given to them in the PurchaseAgreement. 

ARTICLE 2 

AMENDMENT OF THE PURCHASE AGREEMENT 

**2.1 Amendment**. The definition of “**Escrow Amount**” in Section 1.2(p) of the Purchase Agreement shallbe deleted in its entirety and replaced with the following: 

“**Escrow Amount**” means One Millions Dollars($1,000,000). 

ARTICLE 3 

MISCELLANEOUS 

**3.1Interpretation**. The term “Agreement” as used in the Purchase Agreement shall be deemed to refer to the Purchase Agreement as amended hereby. 

**3.2 Continuing Effect of the Purchase Agreement**. This Amendment shall not constitute an amendment or waiver of any provision ofthe Purchase Agreement not expressly referred to herein and the Purchase Agreement shall remain in full force and effect as amended hereby. 

**3.3 Governing Law**. This Amendment and the legal relations between the Parties shallbe governed by and construed in accordance with the Laws of the State of Delaware, without regard to principles of conflicts of Laws that would direct the application of the Laws of another jurisdiction. 

**3.4 Counterparts**. This Amendment may be executed in counterparts, each of which shall be deemed an original instrument, but allsuch counterparts together shall constitute but one agreement. Delivery of an executed counterpart signature page by facsimile or e-mail in portable document format (.pdf) is as effective as executing and delivering this Amendment in the presence ofthe other Parties to this Amendment. 

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IN WITNESS WHEREOF, this Amendment has been signed by each of the Parties as of the date firstabove written. 

 
**SELLERS**:****Rex Energy CorporationBy: 
/s/ Curtis J. Walker
Name: Curtis J. WalkerTitle: Chief Accounting OfficerSand Hills Management, LLCBy: 
/s/ Ned E. Wehler
Name: Ned E. WehlerTitle: Manager**PURCHASER**:****AMERICAN INDUSTRIAL WATER, LLCBy: 
/s/ Mark F. Strauss
Name: Mark F. StraussTitle: SVP, Corporate Strategy and Business Development
 
[Signature Page toAmendment to Membership Interest Purchase Agreement]